Category: Biology

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Structure Of Ecosystem

Ecosystem comprises of two major components. They are:

(i) Abiotic (non-living) components:

It includes climatic factors (air, water, sunlight, rainfall, temperature and humidity), edaphic factors (soil air, soil water and pH of soil), topography (latitude, altitude), organic components (carbohydrates, proteins, lipids and humic substances) and inorganic substances (C, H, O, N and P). Abiotic components play vital role in any ecosystem and hence the total inorganic substances present in any ecosystem at a given time is called standing quality (or) standing state.

(ii) Biotic (living) components:

It includes all living organisms like plants, animals, fungi and bacteria. They form the trophic structures of any ecosystem. On the basis of nutritional relationships, trophic levels of an ecosystem have two components.

• autotrophic components and
• heterotrophic components.

1. Autotrophic components:

Autotrophs are organisms which can manufacture the organic compounds from simple inorganic components through a process called photosynthesis. In most of the ecosystems, green plants are the autotrophs and are also called producers.

2. Heterotrophic components:

These organisms which consume the producers are called consumers and can be recognized into macro and micro consumers. Macroconsumers refer to herbivores, carnivores and omnivores (primary, secondary and tertiary consumers).

Microconsumers are called decomposers. Decomposers are organisms that decompose the dead plants and animals to release organic and inorganic nutrients into the environment which are again reused by plants. Example: Bacteria, Actinomycetes and Fungi.

The amount of living materials present in a population at any given time is known as standing crop, which may be expressed in terms of number or biomass per unit area. Biomass can be measured as fresh weight or dry weight or carbon weight of organisms. Biotic components are essential to construct the food chain, food web and ecological pyramids.

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Dispersal of Seeds and Fruits

Both fruits and seeds possess attractive colour, odour, shape and taste needed for the dispersal by birds, mammals, reptiles, fish, ants and insects even earthworms. The seed consists of an embryo, stored food material and a protective covering called seed coat.

As seeds contain miniature but dormant future plants, their dispersal is an important criterion for distribution and establishment of plants over a wide geographical area. The dissemination of seeds and fruits to various distances from the parent plant is called seed and fruit dispersal.

It takes place with the help of ecological factors such as wind, water and animals. Seed dispersal is a regeneration process of plant populations and a common means of colonizing new areas to avoid seedling level competition and from natural enemies like herbivores, frugivores and pathogens.

Fruit maturation and seed dispersal is inflenced by many ecologically favourable conditions such as Season (Example: Summer), suitable environment, and seasonal availability of dispersal agents like birds, insects etc.

Seeds require agents for dispersal which are crucial in plant community dynamics in many ecosystems around the globe. They offer many benefis to communities such as food and nutrients, migration of seeds across habitats and helps spreading plant genetic diversity.

Dispersal by Wind (Anemochory)

The individual seeds or the whole fruit may be modified to help for the dispersal by wind. Wind dispersal of fruits and seeds is quite common in tall trees. The adaptation of the wind dispersed plants are

• Minute seeds: Seeds are minute, very small, light and with inflted covering. Example: Orchids.
• Wings: Seeds or whole fruits are flattened to form a wing. Examples: Maple, Gyrocarpus, Dipterocarpus and Terminalia
  

Feathery Appendages:

Seeds or fruits may have feathery appendages which greatly increase their buoyancy to disperse to high altitudes. Examples: Vernonia and Asclepias.

Censor mechanisms:

The fruits of many plants open in such a way that the seeds can escape only when the fruit is violently shaken by a strong wind. Examples: Aristolochia and Poppy

Dispersal by Water (Hydrochory)

Dispersal of seeds and fruits by water usually occurs in those plants which grow in or near water bodies. Adaptation of hydrochory are:-

• Obconical receptacle with prominent air spaces. Example: Nelumbo.
• Presence of firous mesocarp and light pericarp. Example: Coconut.
• Seeds are light, small, provided with aril which encloses air.Example: Nymphaea.
• The fruit may be inflted. Examples: Heritiera littoralis.
• Seeds by themselves would not flat may be carried by water current. Example: Coconut
  

Dispersal by Animals (Zoochory)

Birds and mammals, including human beings play an effient and important role in the dispersal of fruit and seeds. They have the following devices.

(i) Hooked fruit:

The surface of the fruit or seeds have hooks,(Xanthium), barbs (Andropogon), spines (Aristida) by means of which they adhere to the body of animals or clothes of human beings and get dispersed.

(ii) Sticky fruits and seeds:

• Some fruits have sticky glandular hairs by which they adhere to the fur of grazing animals. Example: Boerhaavia and Cleome.
• Some fruits have viscid layer which adhere to the beak of the bird which eat them and when they rub them on to the branch of the tree, they disperse and germinate. Example: Cordia and Alangium

(iii) Fleshy fruits:

Some flshy fruits with conspicuous colours are dispersed by human beings to distant places after consumption. Example: Mango and Diplocyclos.

Dispersal by Explosive Mechanism (Autochory)

Some fruits burst suddenly with a force enabling to throw seeds to a little distance away from the plant. Autochory shows the following adaptations.

Mere touch of some plants causes the ripened fruit to explode suddenly and seeds are thrown out with great force. Example: Impatiens (Balsam), Hura.

Some fruits when they come in contact with water particularly after a shower of rain, burst suddenly with a noise and scatter the seeds. Examples: Ruellia and Crossandra.

Certain long pods explode with a loud noise like cracker, scattering the seeds in all directions. Example: Bauhinia vahlii (Camel’s foot climber).

As the fruit matures, tissues around seeds are converted into a mucilaginous fluid, due to which a high turgor pressure develops inside the fruit which leads to the dispersal of seeds. Example: Ecballium elatrium (Squirting cucumber) Gyrocsrpus and Dipterocarpius.

Human aided seed dispersal Seed Ball:

Seed ball is an ancient Japanese technique of encasing seeds in a mixture of clay and soil humus (also in cow dung) and scattering them on to suitable ground, not planting of trees manually. This method is suitable for barren and degraded lands for tree regeneration and vegetation before monsoon period where the suitable dispersal agents become rare.

Advantages of seed dispersal:

• Seeds escape from mortality near the parent plants due to predation by animals or getting diseases and also avoiding competition.
• Dispersal also gives a chance to occupy favourable sites for growth.
• It is an important process in the movement of plant genes particularly this is the only method available for self-fertilized flowers and maternally transmitted genes in outcrossing plants.
• Seed dispersal by animals help in conservation of many species even in human altered ecosystems.
• Understanding of fruits and seed dispersal acts as a key for proper functioning and establishment of many ecosystems from deserts to evergreen forests and also for the maintenance of biodiversity conservation and restoration of ecosystems.

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Ecological Adaptations | Hydrophytes | Xerophytes | Mesophytes | Epiphytes | Halophytes

The modifications in the structure of organisms to survive successfully in an environment are called adaptations of organisms. Adaptations help the organisms to exist under the prevailing ecological habitat. Based on the habitats and the corresponding adaptations of plants, they are classified as hydrophytes, xerophytes, mesophytes, epiphytes and halophytes.

Hydrophytes

The plants which are living in water or wet places are called hydrophytes. According to their relation to water and air, they are subdivided into following categories:

1. Free floating hydrophytes
2. Rooted – floating hydrophytes
3. Submerged floating hydrophytes
4. Rooted – submerged hydrophytes
5. Amphibious hydrophytes.

1. Free floating hydrophytes:

These plants float freely on the surface of water. They remain in contact with water and air, but not with soil. Examples: Eichhornia, Pistia and Wolffia (smallest flowering plant).

2. Rooted flating hydrophytes:

In these plants, the roots are field in mud, but their leaves and flowers are flating on the surface of water. These plants are in contact with soil, water and air. Examples: Nelumbo, Nymphaea, Potomogeton and Marsilea. Lotus seeds show highest longevity in plant kingdom.

3. Submerged flating hydrophytes:

These plants are completely submerged in water and not in contact with soil and air. Examples: Ceratophyllum and Utricularia.

4. Rooted – submerged hydrophytes:

These plants are completely submerged in water and rooted in soil and not in contact with air.
Examples: Hydrilla, Vallisneria and Isoetes.

5. Amphibious hydrophytes (Rooted emergent hydrophytes):

These plants are adapted to both aquatic and terrestrial modes of life. They grow in shallow water. Examples: Ranunculus, Typha and Sagittaria.

Hygrophytes:

The plants which can grow in moist damp and shady places are called hygrophytes. Examples: Habenaria (Orchid), Mosses (Bryophytes), etc.

Morphological adaptations of Hydrophytes: In root

• Roots are totally absent in Wolff and Salvinia or poorly developed in Hydrilla or well developed in Ranunculus.
• The root caps are replaced by root pockets. Example: Eichhornia

In stem

• The stem is long, slender, spongy and flexible in submerged forms.
• In free flating forms the stem is thick, short stoloniferous and spongy; and in rooted floating forms, it is a rhizome.
• Vegetative propagation is through runners, stolon, stem and root cuttings, tubers, dormant apices and offets.

In leaves

• The leaves are thin, long and ribbon shaped in Vallisneria or long and linear in Potamogeton or finely dissected in Ceratophyllum.
• The floating leaves are large and flat as in Nymphaea and Nelumbo. In Eichhornia and Trapa petioles become swollen and spongy.
• In emergent forms, the leaves show heterophylly (Submerged leaves are dissected and aerial leaves are entire).

Example: Ranunculus, Limnophila heterophylla and Sagittaria

Anatomical adaptations

• Cuticle is either completely absent or if present it is thin and poorly developed
• Single layer of epidermis is present
• Cortex is well developed with aerenchyma
• Vascular tissues are poorly developed. In emergent forms vascular elements are well developed.
• Mechanical tissues are generally absent except in some emergent forms. Pith cells are sclerenchymatous.
  

Physiological adaptations of Hydrophytes:

• Hydrophytes have the ability to withstand anaerobic conditions.
• They possess special aerating organs.

Xerophytes

The plants which are living in dry or xeric condition are known as Xerophytes. Xerophytic habitat can be of two different types. They are:

a. Physical dryness:

In these habitats, soil has a little amount of water due to the inability of the soil to hold water because of low rainfall.

b. Physiological dryness:

In these habitats, water is suffiently present but plants are unable to absorb it because of the absence of capillary spaces. Example: Plants in salty and acidic soil. Based on adaptive characters xerophytes are classified into three categories. They are Ephemerals, Succulents and Non succulent plants.

(i) Ephemerals:

These are also called drought escapers or drought evaders. These plants complete their life cycle within a short period (single season). These are not true xerophytes. Examples: Argemone, Mollugo, Tribulus and Tephrosia.

(ii) Succulents:

These are also called drought enduring plants. These plants store water in their plant parts during the dry period. These plants develop certain adaptive characters to resist extreme drought conditions. Examples: Opuntia, Aloe, Bryophyllum and Begonia.

(iii) Non succulents:

These are also called drought resistant plants (true xerophytes). They face both external and internal dryness. They have many adaptations to resist dry conditions. Examples: Casuarina, Nerium, Zizyphus and Acacia.

Morphological Adaptations In root

• Root system is well developed and is greater than that of shoot system.
• Root hairs and root caps are also well developed.

In xerophytic plants with the leaves and stem are covered with hairs are called trichophyllous plants. Example: Cucurbits (Melothria and Mukia)

In stem

• Stems are mostly hard and woody. They may be aerial or underground.
• The stems and leaves are covered with wax coating or covered with dense hairs.
• In some xerophytes all the internodes in the stem are modifid into a flashy leaf structure called phylloclades (Opuntia).
• In some of the others single or occasionally two internodes modifid into flashy green structure called cladode (Asparagus).

In some the petiole is modifid into a flashy leaf like structure called phyllode (Acacia melanoxylon).

In leaves

• Leaves are generally leathery and shiny to reflect light and heat.
• In some plants like Euphorbia, Acacia, Ziziphus and Capparis, the stipules are modified into spines.
• The entire leaves are modifid into spines (Opuntia) or reduced to scales (Asparagus).

Anatomical adaptations

• Presence of multilayered epidermis with heavy cuticle to prevent water loss due to transpiration.
• Hypodermis is well developed with sclerenchymatous tissues.
• Sunken stomata are present only in the lower epidermis with hairs in the sunken pits.
• Scotoactive type of stomata found in succulent plants.
• Vascular bundles are well developed with several layered bundle sheath.
• Mesophyll is well diffrentiated into palisade and spongy parenchyma.
• In succulents the stem possesses a water storage region.
  

Physiological adaptations

• Most of the physiological processes are designed to reduce transpiration.
• Life cycle is completed within a short period (Ephemerals).

Mesophytes

The plants which are living in moderate conditions (neither too wet nor too dry) are known as mesophytes. These are common land plants. Example: Maize and Hibiscus.

Morphological adaptations

• Root system is well developed with root caps and root hairs.
• Stems are generally aerial, stout and highly branched.
• Leaves are generally large, broad, thin with different shapes.

Anatomical adaptations

• Cuticle in aerial parts are moderately developed.
• Epidermis is well developed and stomata are generally present on both the epidermis.
• Mesophyll is well diffrentiated into palisade and spongy parenchyma.
• Vascular and mechanical tissues are fairly developed and well diffrentiated.

Physiological adaptations

• All physiological processes are normal.
• Temporary wilting takes place at room temperature when there is water scarcity.

Tropophytes are plants which behave as xerophytes at summer and behave as mesophytes (or) hydrophytes during rainy season.

Epiphytes

Epiphytes are plants which grow perched on other plants (Supporting plants). They use the supporting plants only as shelter and not for water or food supply. These epiphytes are commonly seen in tropical rain forests. Examples: Orchids, Lianas, Hanging Mosses and Money plant.

Morphological adaptations

• Root system is extensively developed. These roots may be of two types. They are Clinging roots and Aerial roots. Clinging roots fix the epiphytes firmly on the surface of the supporting objects.
• Aerial roots are green coloured roots which may hang downwardly and absorb moisture from the atmosphere with the help of a spongy tissue called velamen.
• Stem of some epiphytes are succulent and develop pseudobulb or tuber.
• Generally the leaves are lesser in number and may be fleshy and leathery.
• Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the predators.
• The fruits and seeds are very small and usually dispersed by wind, insects and birds.

Anatomical adaptations

• Multilayered epidermis is present. Inner to the velamen tissue, the peculiar exodermis layer is present.
• Presence of thick cuticle and sunken stomata greatly reduces transpiration.
• Succulent epiphytes contain well developed parenchymatous cells to store water.
  

Physiological adaptations

Special absorption processes of water by velamen tissue.

Halophytes

There are special type of Halophytic plants which grow on soils with high concentration of salts. Examples: Rhizophora, Sonneratia and Avicennia.

Halophytes are usually found near the seashores and Estuaries. The soils are physically wet but physiologically dry. As plants cannot use salt water directly they require filtration of salt using physiological processes. This vegetation is also known as mangrove forest and the plants are called mangroves.

Morphological adaptations

• The temperate halophytes are herbaceous but the tropical halophytes are mostly bushy
• In addition to the normal roots, many stilt roots are developed
• A special type of negatively geotropic roots called pneumatophores with pneumathodes to get sufficient aeration are also present. They are called breathing roots. Example: Avicennia
  
• Presence of thick cuticle on the aerial parts of the plant body
• Leaves are thick, entire, succulent and glossy. Some species are aphyllous (without leaves).
  
• Viviparous mode of seed germination is found in halophytes
  

Anatomical adaptations

• Epidermal cells of stem is heavy cutinized, almost squarish and are filled with oil and tannins.
• ‘Star’ shaped sclereids and ‘H’ shaped heavy thickened spicules that provide mechanical strength to cortex are present in the stem.
• The leaves may be dorsiventral or isobilateral with salt secreting glands.

Physiological adaptations

• High osmotic pressure exists in some plants.
• Seeds germinate in the fruits while on the mother plant (Vivipary).

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Ecological Factors | Climatic Factors | Edaphic Factors | Topographic Factors | Biotic Factors

Many organisms, co-exist in an environment. The environment (surrounding) includes physical, chemical and biological components. When a component surrounding an organism affects the life of an organism, it becomes a factor.

All such factors together are called environmental factors or ecological factors. These factors can be classified into living (biotic) and non-living (abiotic) which make the environment of an organism. However the ecological factors are meaningfully grouped into four classes, which are as follows:

• Climatic factors
• Edaphic factors
• Topographic factors
• Biotic factors

We will discuss the above factors in a concise manner.

Climatic Factors

Climate is one of the important natural factors controlling the plant life. The climatic factors includes light, temperature, water, wind and fire.

a. Light

Light is a well known factor needed for the basic physiological processes of plants, such as photosynthesis, transpiration, seed germination and flowering. The portion of the sunlight which can be resolved by the human eye is called visible light.

The visible part of light is madeup of wavelength from about 400 nm (violet) to 700 nm (red). The rate of photosynthesis is maximum at blue (400 – 500 nm) and red (600 – 700 nm). The green (500 – 600 nm) wave length of spectrum is less strongly absorbed by plants.

Based on the tolerance to intensities of light, the plants are divided into two types. They are:-

• Heliophytes – Light loving plants. Example: Angiosperms.
• Sciophytes – Shade loving plants. Example: Bryophytes and Pteridophytes.

b. Temperature

Temperature is one of the important factors which affect almost all the metabolic activities of an organism. Every physiological process in an organism requires an optimum temperature at which it shows the maximum metabolic rate. Three limits of temperature can be recognized for any organism. They are

• Minimum temperature – Physiological activities are lowest.
• Optimum temperature – Physiological activities are maximum.
• Maximum temperature – Physiological activities will stop.

Based on the temperature prevailing in an area, Raunkiaer classified the world’s vegetation into the following four types. They are megatherms, mesotherms, microtherms and hekistotherms. In thermal springs and deep sea hydrothermal vents the average temperature exceed 100°c. Based on the range of thermal tolerance, organisms are divided into two types.

1. Eurythermal:

Organisms which can tolerate a wide range of temperature fluctuations.
Example: Zostera (A marine Angiosperm) and Artemisia tridentata.

2. Stenothermal:

Organisms which can tolerate only small range of temperature variations. Example: Mango and Palm (Terrestrial Angiosperms). Mango plant does not grow in temperate countries like Canada and Germany.

Thermal Stratifiation:

It is usually found in aquatic habitat. The change in the temperature profile with increasing depth in a water body is called thermal stratifiation. There are three levels of thermal stratifiations.

• Epilimnion – The upper layer of warmer water.
• Metalimnion – The middle layer with a zone of gradual decrease in temperature.
• Hypolimnion – The bottom layer of colder water.

Temperature based zonation

Variations in latitude and altitude do affect the temperature and the vegetation on the earth surface. The latitudinal and altitudinal zonation of vegetation is illustrated below:

Latitude:
Latitude is an angle which ranges from 0° at the equator to 90° at the place.

Altitude:
How high a place is located above the sea level is called the altitude of the place.

Timber line/Tree line:
It is an imaginary line in a mountain or higher areas of land that marks the level above which trees do not grow. The altitudinal limit of normal tree growth is about 3000 to 4000m.

Effects of temperature

The following physiological processes are inflenced by temperature:

• Temperature affcts the enzymatic action of all the bio-chemical reactions in a plant body.
• It inflences CO₂ and O₂ solubility in the biological systems. Increases respiration and stimulates growth of seedlings.
• Low temperature with high humidity can cause spread of diseases in plants.
• The varying temperature with moisture determines the distribution of the vegetation types.

c. Water

Water is one of the most important climatic factors. It affects the vital processes of all living organisms. It is believed that even life had originated only in water during the evolution of Earth. Water covers more than 70% of the earth’s surface. In nature, water is available to plants in three ways. They are atmospheric moisture, precipitation and soil water.

The productivity and distribution of plants depend upon the availability of water. Further the quality of water is also important especially for the aquatic organisms. The total amount of water salinity in different water bodies are:

• 5% in inland water (Fresh water)
• 30 – 35% in sea water and
• More than 100% in hypersaline water (Lagoons) Based on the range of tolerance of salinity, organisms are divided into two types.

1. Euryhaline:
Organisms which can live in water with wide range of salinity. Examples: Marine algae and marina angiosperms

2. Stenohaline:
Organisms which can withstand only small range of salinity. Example: Plants of estuaries.

Examples of tolerance to toxicity

(i) Soyabean and tomato manage to tolerate presence of cadmium poisoning by isolating cadmium and storing into few group of cells and prevent cadmium affcting other cells.

(ii) Rice and Eichhornia (water hyacinth) tolerate cadmium by binding it to their proteins. These plants otherwise can also be used to remove cadmium from contaminated soil, this is known as Phytoremediation.

d. Wind

Air in motion is called wind. It is also a vital ecological factor. The atmospheric air contains a number of gases, particles and other constituents. The composition of gases in atmosphere is as follows: Nitrogen – 78% , Oxygen – 21%, Carbon-di-oxide – 0.03%, Argon and other gases – 0.93%. The other components of wind are water vapour, gaseous pollutants, dust, smoke particles, microorganisms, pollen grains, spores, etc. Anemometer is the instrument used to measure the speed of wind.

Effects of wind

• Wind is an important factor for the formation of rain
• Causes wave formation in lakes and ocean, promotes aeration of water
• Strong wind causes soil erosion and reduces soil fertility
• Increases the rate of transpiration
• Helps in pollination in anemophilous plants
• It also helps in dispersal of many fruits, seeds, spores, etc.
• Strong wind may cause up-rooting of big trees
• Unidirectional wind stimulates the development of flag forms in trees.
  

e. Fire

Fire is an exothermic factor caused due to the chemical process of combustion, releasing heat and light. It is mostly man-made and sometimes develops naturally due to the friction between the tree surfaces. Fire is generally divided into

• Ground fie – Which is flameless and subterranean.
• Surface fie – Which consumes the herbs and shrubs.
• Crown fie – Which burns the forest canopy.

Effects of fie

• Fire has a direct lethal effect on plants
• Burning scars are the suitable places for the entry of parasitic fungi and insects
• It brings out the alteration of light, rainfall, nutrient cycle, fertility of soil, pH, soil flora and fauna
• Some fungi which grow in soil of burnt areas called pyrophilous. Example: Pyronema conflens.

Edaphic factors

Edaphic factors, the abiotic factors related to soil, include the physical and chemical composition of the soil formed in a particular area. The study of soils is called Pedology.

The soil

Soil is the weathered superfiial layer of the Earth in which plants can grow. It is a complex composite mass consisting of soil constituents, soil water, soil air and soil organisms, etc.

Soil formation

Soil originates from rocks and develops gradually at different rates, depending upon the ecological and climatic conditions. Soil formation is initiated by the weathering process. Biological weathering takes place when organisms like bacteria, fungi, lichens and plants help in the breakdown of rocks through the production of acids and certain chemical substances.

Soil types

Based on soil formation (pedogenesis), the soils are divided into

• Residual soils – These are soils formed by weathering and pedogenesis of the rock.
• Transported soils – These are transported by various agencies.

The important edaphic factors which affect vegetation are as follows:

1. Soil moisture:
Plants absorbs rain water and moisture directly from the air

2. Soil water:
Soil water is more important than any other ecological factors affecting the distribution of plants. Rain is the main source of soil water. Capillary water held between pore spaces of soil particles and angles between them is the most important form of water available to the plants.

3. Soil reactions:
Soil may be acidic or alkaline or neutral in their reaction. pH value of the soil solution determines the availability of plant nutrients. The best pH range of the soil for cultivation of crop plants is 5.5 to 6.8.

4. Soil nutrients:
Soil fertility and productivity is the ability of soil to provide all essential plant nutrients such as minerals and organic nutrients in the form of ions.

5. Soil temperature:
Soil temperature of an area plays an important role in determining the geographical distribution of plants. Low temperature reduces use of water and solute absorption by roots.

6. Soil atmosphere:
The spaces left between soil particles are called pore spaces which contains oxygen and carbon-di-oxide.

7. Soil organisms:
Many organisms existing in the soil like bacteria, fungi, algae, protozoans, nematodes, insects, earthworms, etc. are called soil organisms.

Soil Profie

Soil is commonly stratified into horizons at different depth. These layers differ in their physical, chemical and biological properties. This succession of super-imposed horizons is called soil profie.

Types of soil particles

Based on the relative proportion of soil particles, four types of soil are recognized.

Loamy soil is ideal soil for cultivation. It consists of 70% sand and 30% clay or silt or both. It ensures good retention and proper drainage of water. Th porosity of soil provides adequate aeration and allows the penetration of roots.

Based on the water retention, aeration and mineral contents of soil, the distribution of vegetation is divided into following types.

• Halophytes: Plants living in saline soils
• Psammophytes: Plants living in sandy soils
• Lithophytes: Plants living on rocky surface
• Chasmophytes: Plants living in rocky crevices
• Cryptophytes: Plants living below the soil surface
• Cryophytes: Plants living on surface of ice
• Oxylophytes: Plants living in acidic soil
• Calciphytes: Plants living in calcium rich alkaline soil

Topographic factors

The surface features of earth are called topography. Topographic influence on the climate of any area is determined by the interaction of solar radiation, temperature, humidity, rainfall, latitude and altitude. It affects the vegetation through climatic variations in small areas (micro climate) and even changes the soil conditions. Topographic factors include latitude, altitude, direction of mountain, steepness of mountain etc.

a. Latitudes and altitudes

Latitudes represent distance from the equator. Temperature values are maximum at the equator and decrease gradually towards poles. Different types of vegetation occur from equator to poles which are illustrated below.

Height above the sea level forms the altitude. At high altitudes, the velocity of wind remains high, temperature and air pressure decrease while humidity and intensity of light increases. Due to these factors, vegetation at different altitudes varies, showing distinct zonation.

b. Direction of Mountain

North and south faces of mountain or hill possess different types of flra and fauna because they differ in their humidity, rainfall, light intensity, light duration and temperature regions.

Ecotone – The transition zone between two ecosystems.
Example: The border between forest and grassland.

Edge effect – Spices found in ecotone areas are unique due to the effect of the two habitats. This is called edge effect. Example: Owl in the ecotone area between forest and grassland.

The two faces of the mountain or hill receive different amount of solar radiation, wind action and rain. Of these two faces, the windward region possesses good vegetation due to heavy rains and the leeward region possesses poor vegetation due to rain shadows (rain defit).

Similarly in the soil of aquatic bodies like ponds the center and edge possess different depth of water due to soil slope and different wave actions in the water body. Therefore, different parts of the same area may possess different species of organisms.

c. Steepness of the mountain

The steepness of the mountain or hill allows the rain to run off As a result the loss of water causes water deficit and quick erosion of the top soil resulting in poor vegetation. On the other hand, the plains and valley are rich in vegetation due to the slow drain of surface water and better retention of water in the soil.

Biotic factors

The interactions among living organisms such as plants and animals are called biotic factors, which may cause marked effects upon vegetation. The effcts may be direct and indirect and modifies the environment. The plants mostly which lives together in a community and influence one another. Similarly, animals in association with plants also affect the plant life in one or several ways.

The different interactions among them can be classified into following two types they are positive interaction and negative interaction Positive interactions When one or both the participating species are benefied, it is positive interaction. Examples; Mutualism and Commensalism.

a. Mutualism:

It is an interaction between two species of organisms in which both are benefited from the obligate association. The following are common examples of mutualism.

Nitrogen fiation

Rhizobium (Bacterium) forms nodules in the roots of leguminous plants and lives symbiotically. The Rhizobium obtains food from leguminous plant and in turn fies atmospheric nitrogen into nitrate, making it available to host plants.

Other examples:

• Water fern (Azolla) and Nitrogen fixing Cyanobacterium (Anabaena).
• Anabaena present in coralloid roots of Cycas. (Gymnosperm)
• Cyanobacterium (Nostoc) found in the thalloid body of Anthoceros. (Bryophytes)
• Wasps present in fruits of fig.
• Lichen is a mutual association of an alga and a fungus.
• Roots of terrestrial plants and fungal hyphae – Mycorrhiza

b. Commensalism:

It is an interaction between two organisms in which one is benefitted and the other is neither benefited nor harmed. The species that derives benefit is called the commensal, while the other species is called the host. The common examples of commensalism are listed below:

Epiphytes

The plants which are found growing on other plants without harming them are called epiphytes. They are commonly found in tropical rain forest.

The epiphytic higher plant (Orchid) gets its nutrients and water from the atmosphere with the help of the hygroscopic roots which contain special type of spongy tissue called Velamen. It prepares its own food and does not depend on the host. Using the host plant only they support and does not harm it in any way.

• Many orchids, ferns, lianas, hanging mosses, Peperomia, money plant and Usnea (Lichen) are some of the examples of epiphytes.
• Spanish Moss – Tillandsia grows on the bark of Oak and Pine trees.

Negative interactions

When one of the interacting species is benefitted and the other is harmed, it is called negative interaction. Examples: predation, parasitism, competition and amensalism.

a. Predation:

It is an interaction between two species, one of which captures, kills and eats up the other. The species which kills is called a predator and the species which is killed is called a prey. The predator is benefitted while the prey is harmed.

Examples:

A number of plants like Drosera (Sun dew plant), Nepenthes (Pitcher Plant), Dionaea (Venus fly trap), Utricularia (Bladder wort) and Sarracenia are predators which consume insects and other small animals for their food as a source of nitrogen. They are also called as insectivorous plants.

Many herbivores are predators. Cattles, Camels, Goats etc., frequently browse on the tender shoots of herbs, shrubs and trees. Generally annuals suffer more than the perennials. Grazing and browsing may cause remarkable changes in vegetation. Nearly 25 percent of all insects are known as phytophagous (feeds on plant sap and other parts of plant)

Many defense mechanisms are evolved to avoid their predations by plants. Examples: Calotropis produces highly poisonous cardiac glycosides, Tobacco produces nicotine, coffe plants produce caffine, Cinchona plant produces quinine. Throns of Bougainvillea, spines of Opuntia, and latex of cacti also protect them from predators.

b. Parasitism:

It is an interaction between two different species in which the smaller partner (parasite) obtains food from the larger partner (host or plant). So the parasitic species is benefied while the host species is harmed. Based on the host-parasite relationship, parasitism is classified into two types they are holoparasite and hemiparasite.

Holoparasites

The organisms which are dependent upon the host plants for their entire nutrition are called Holoparasites. They are also called total parasites.

Examples:

• Cuscuta is a total stem parasite of the host plant Acacia, Duranta and many other plants. Cuscuta even gets flower inducing hormone from its host plant.
• Balanophora, Orobanche and Rafflia are the total root parasites found on higher plants.

Hemiparasites

The organisms which derive only water and minerals from their host plant while synthesizing their own food by photosynthesis are called Hemiparasites. They are also called partial parasites.

Examples:

• Viscum and Loranthus are partial stem parasites.
• Santalum (Sandal Wood) is a partial root parasite.

The parasitic plants produce the haustorial roots inside the host plant to absorb nutrients from the vascular tissues of host plants.

c. Competition:

It is an interaction between two organisms or species in which both the organisms or species are harmed. Competition is the severest in population that has irregular distribution. Competition is classified into intraspecific and interspecific.

1. Intraspecific competition:

It is an interaction between individuals of the same species. This competition is very severe because all the members of species have similar requirements of food, habitat, pollination etc. and they also have similar adaptations to fulfill their needs.

2. Interspecific competition:

It is an interaction between individuals of different species. In grassland, many species of grasses grow well as there is little competition when enough nutrients and water is available.

During drought shortage of water occurs. A life and death competition starts among the different species of grass lands. Survival in both these competitions is determined by the quantity of nutrients, availability of water and migration to new areas.

Different species of herbivores, larvae and grass hopper competing for fodder or forage plants. Trees, shrubs and herbs in a forest struggle for sunlight, water and nutrients and also for pollination and dispersal of fruits and seeds. The Utricularia (Bladderwort) competes with tiny fishes for small crustaceans and insects.

d. Amensalism:

It is an interspecific interaction in which one species is inhibited while the other species is neither benefited nor harmed. The inhibition is achieved by the secretion of certain chemicals called allelopathic substances. Amensalism is also called antibiosis.

• Penicillium notatum produces penicillin to inhibit the growth of a variety of bacteria especially Staphylococcus.
• Trichoderma inhibits the growth of fungus Aspergillus.
• Roots and hulls of Black Walnut Juglans nigra secretes an alkaloid Juglone which inhibits the growth of seedlings of Apple, Tomato and Alfalfa around it.

Interspecific interactions / Co-evolutionary dynamics

i. Mimicry:

It is a phenomenon in which living organism modifis its form, appearance, structure or behaviour and looks like another living organism as a self defence and increases the chance of its survival. Floral mimicry is for usually inviting pollinators but animal mimicry is often protective. Mimicry is a result of evolutionary signifiance due to shape and sudden heritable mutation and preservation by natural selection.

Example:

• The plant, Ophrys an orchid, the flower looks like a female insect to attract the male insect to get pollinated by the male insect and it is otherwise called ‘floral mimicry’.
• Carausium morosus – stick insect or walking stick. It is a protective mimicry.
• Phyllium frondosum – leaf insect, another example of protective mimicry.

ii. Myrmecophily:

Sometimes, ants take their shelter on some trees such as Mango, Litchi, Jamun, Acacia etc. These ants act as body guards of the plants against any disturbing agent and the plants in turn provide food and shelter to these ants. This phenomenon is known as Myrmecophily. Example: Acacia and acacia ants.

iii. Co-evolution:

The interaction between organisms, when continues for generations, involves reciprocal changes in genetic and morphological characters of both organisms. This type of evolution is called Co-evolution. It is a kind of co-adaptation and mutual change among interactive species. Examples:

Corolla length and proboscis length of butterfles and moths (Habenaria and Moth).

• Bird’s beak shape and flower shape and size.
• More examples: Horn bills and birds of Scrub jungles, Slit size of pollinia of Apocynaceae members and leg size of insects.

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Principles of Ecology

The term “ecology” (oekologie) is derived from two Greek words – oikos (meaning house or dwelling place and logos meaning study) It was first proposed by Reiter (1868). However, the most widely accepted defiition of ecology was given by Ernest Haeckel (1869).

Alexandar von Humbolt – Father of Ecology
Eugene P. Odum – Father of modern Ecology
R. Misra – Father of Indian Ecology

Definitions of ecology

“The study of living organisms, both plants and animals, in their natural habitats or homes.” – Reiter (1885)

“Ecology is the study of the reciprocal relationship between living organisms and their environment.” – Earnest Haeckel (1889)

Ecological hierarchy

The interaction of organisms with their environment results in the establishment of grouping of organisms which is called ecological hierarchy or ecological levels of organization.

The basic unit of ecological hierarchy is an individual organism. The hierarchy of ecological systems is illustrated below:

Branches of Ecology:

Ecology is mainly divided into two branches, they are autecology and synecology.

• Autecology is the ecology of an individual species and is also called species ecology.
• Synecology is the ecology of a population or community with one or more species and also called as community ecology.

Many advances and developments in the field ecology resulted in various new dimensions and branches. Some of the advanced fields are Molecular ecology, Eco technology, Statistical ecology and Environmental toxicology.

Habitat and Niche

Habitat

Habitat is a specifi physical place or locality occupied by an organism or any species which has a particular combination of abiotic or environmental factors. But the environment of any community is called Biotope.

Niche

An ecological niche refers to an organism’s place in the biotic environment and its functional role in an ecosystem. The term was coined by the naturalist Roswell Hill Johnson but Grinell (1917) was probably first to use this term. The habitat and niche of any organism is called Ecotope.

The differences between habitat and niche are as follows.

Ecological equivalents

Taxonomically diffrent species occupying similar habitats (Niches) in diffrent geographical regions are called Ecological equivalents.

Examples:

• Certain species of epiphytic orchids of Western Ghats of India differ from the epiphytic orchids of South America. But they are epiphytes.
• Species of the grass lands of Western Ghats of India differ from the grass species of temperate grass lands of Steppe in North America. But they are all ecologically primary producers and fulfiling similar roles in their respective communities.

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Future Biotechnology

Biotechnology has become a comprehensive scientific venture from the point of academic and commercial angles, within a short time with the sequencing of human genome and genome of some important organisms. The future developments in biotechnology will be exciting. Thus the development in biotechnology will lead to a new scientific revolution that would change the lives and future of people.

Like industrial and computer revolution, biotechnological revolution will also promise major changes in many aspects of modern life.

Biotechnology is also revolutionizing the diagnosis of diseases caused by genetic factors. New tests can detect changes in the DNA sequence of genes associated with disease risk and can predict the likelihood that a patient will develop a disease.

The ability of therapeutics and vaccines to treat and prevent diseases has been well documented. Biotechnology has been central to these advances, progressively offering the ability to make more complicated medicines and vaccines, opening up the treatment and prevention of a broader set of diseases.

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Intellectual Rights of Property (Ipr), Biosafety and Bioethics

Intellectual property right (IPR) is a category of rights that includes intangible creation of the human intellect, and primarily consists of copyrights, patents, and trademarks. It also includes other types of rights, such as trade secrets, publicity rights, moral rights, and rights against unfair competition.

In biotechnology, the transformed microorganisms and plants and technologies for the production of commercial products are exclusively the property of the discoverer. The discoverer has the full rights on his property. It should not be neglected by the others without legal permission.

The right of discoverer must be protected and it does by certain laws framed by a country. The IPR is protected by different ways like patents, copyrights, trade secrets and trademarks, designs and geographical indications.

Patents

It is a special right to the discoverer/inventor that has been granted by the government through legislation for trading new articles. A patent is a personal property which can be licensed or sold by the person or organisation just like any other property. Patent terms give the inventor the rights to exclude others from making, using or selling his invention.

Biosafety and Bioethics

Advances in biotechnology and their applications deals with genetic manipulation.

Biosafety

Biosafety is the prevention of large-scale loss of biological integrity, focusing both on ecology and human health. These prevention mechanisms include conduction of regular reviews of the biosafety in laboratory settings, as well as strict guidelines to follow. Many laboratories handling biohazards employ an ongoing risk management assessment and enforcement process for biosafety. Failures to follow such protocols can lead to increased risk of exposure to biohazards or pathogens.

Bioethics – Ethical, Legal and Social Implications (ELSI)

Bioethics refers to the study of ethical issues emerging from advances in biology and medicine. It is also a moral discernment as it relates to medical policy and practice. Bioethicists are concerned with the ethical questions that arise in the relationships among life sciences, biotechnology and medicine. It includes the study of values relating to primary care and other branches of medicine.

The scope of bioethics is directly related to biotechnology, including cloning, gene therapy, life extension, human genetic engineering, astroethics life in space, and manipulation of basic biology through altered DNA, RNA and proteins.

These developments in biotechnology will affect future evolution, and may require new principles, such as biotic ethics, that values life and its basic biological characters and structures. The Ethical, Legal, and Social Implications (ELSI) program was founded in 1990 as an integral part of the Human Genome Project.

The mission of the ELSI program was to identify and address issues raised by genomic research that would affect individuals, families, and society. A percentage of the Human Genome Project budget at the National Institutes of Health and the U.S. Department of Energy was devoted to ELSI research.

Genetic Engineering Appraisal Committee (GEAC)

GEAC is an apex body under Ministry of Environment, Forests and Climate change for regulating manufacturing, use, import, export and storage of hazardous microbes or genetically modifid organisms (GMOs) and cells in the country. It was established as an apex body to accord approval of activities involving large scale use of hazardous microorganisms and recombinants in research and industrial production.

The GEAC is also responsible for approval of proposals relating to release of genetically engineered organisms and products into the environment including experimental field trials.

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Conservation of Plant Genetic Resources

Germplasm Conservation

Germplasm conservation refers to the conservation of living genetic resources like pollen, seeds or tissue of plant material maintained for the purpose of selective plant breeding, preservation in live condition and used for many research works. Germplasm conservation resources is a part of collection of seeds and pollen that are stored in seed or pollen banks, so as to maintain their viability and fertility for any later use such as hybridization and crop improvement.

Germplasm conservation may also involve a gene bank, DNA bank of elite breeding lines of plant resources for the maintenance of biological diversity and also for food security.

Cryopreservation (- 195.C)

Cryopreservation, also known as Cryoconservation, is a process by which protoplasts, cells, tissues, organelles, organs, extracellular matrix, enzymes or any other biological materials are subjected to preservation by cooling to very low temperature of – 196°C using liquid nitrogen.

At this extreme low temperature any enzymatic or chemical activity of the biological material will be totally stopped and this leads to preservation of material in dormant status. Later these materials can be activated by bringing to room temperature slowly for any experimental work.

Protective agents like dimethyl sulphoxide, glycerol or sucrose are added before cryopreservation process. These protective agents are called cryoprotectants, since they protect the cells, or tissues from the stress of freezing temperature.

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Applications of Plant Tissue Culture

Plant tissue culture techniques have several applications such as:

• Improved hybrids production through somatic hybridization.
• Somatic embryoids can be encapsulated into synthetic seeds (synseeds). These encapsulated seeds or synthetic seeds help in conservation of plant biodiversity.
• Production of disease resistant plants through meristem and shoot tip culture.
• Production of stress resistant plants like herbicide tolerant, heat tolerant plants.
• Micropropagation technique to obtain large numbers of plantlets of both crop and tree species useful in forestry within a short span of time and all through the year.
• Production of secondary metabolites from cell culture utilized in pharmaceutical, cosmetic and food industries.

Micropropagation of Banana

Micropropagation of plants at industrial level maintains high standards of homogeneity in plants like pineapple, banana, strawberry and potato.

Artificial Seed

Artificial seeds or synthetic seeds (synseeds) are produced by using embryoids (somatic embryos) obtained through in vitro culture. They may even be derived from single cells from any part of the plant that later divide to form cell mass containing dense cytoplasm, large nuclceus, starch grains, proteins, and oils etc., To prepare the artifiial seeds different inert materials are used for coating the somatic embryoids like agrose and sodium alginate.

Advantages of Artifiial seeds

Artifiial seeds have many advantages over the true seeds

• Millions of artifiial seeds can be produced at any time at low cost.
• They provide an easy method to produce genetically engineered plants with desirable traits.
• It is easy to test the genotype of plants.
• They can potentially stored for long time under cryopreservation method.
• Artificial seeds produce identical plants
• The period of dormancy of artificial seeds is greatly reduced, hence growth is faster with a shortened life cycle.

Virus-free plants

The filed grown plants like perennial crops, usually are infected by variety of pathogens like fungi, bacteria, mycoplasma, viruses which cause considerable economic losses. Chemical methods can be used to control fungal and bacterial pathogens, but not viruses generally. Shoot meristem tip culture is the method to produce virus-free plants, because the shoot meristem tip is always free from viruses.

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Plant Regeneration Pathway

From the explants, plants can be regenerated by somatic embryogenesis or organogenesis.

Somatic Embryogenesis

Somatic embryogenesis is the formation of embryos from the callus tissue directly and these embryos are called Embryoids or from then in vitro cells directly form pre-embryonic cells which diffrentiate into embryoids.

Applications

• Somatic embryogenesis provides potential plantlets which after hardening period can establish into plants.
• Somatic embryoids can be be used for the production of synthetic seeds.
• Somatic embryogenesis is now reported in many plants such as Allium sativum, Hordeum vulgare, Oryza sativa, Zea mays and this possible in any plant.

Organogenesis

The morphological changes occur in the callus leading to the formation of shoot and roots is called organogenesis.

• Organogenesis can be induced in vitro by introducing plant growth regulators in the MS medium.
• Auxin and cytokinins induce shoot and root formation.

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Plant Tissue Culture Techniques and Types

Plant Tissue Culture (PTC)

Plant tissue culture is used to describe the in vitro and aseptic growth of any plant part on a tissue culture medium. This technology is based on three fundamental principles:

• The plant part or explant must be selected and isolated from the rest of plant body.
• The explant must be maintained in controlled physically (environmental) and chemically defined (nutrient medium) conditions.

Laboratory Facilities for PTC

For PTC, the laboratory must have the following facilities:

• Washing facility for glassware and ovens for drying glassware.
• Medium preparation room with autoclave, electronic balance and pH meter.
• Transfer area sterile room with laminar air-flw bench and a positive pressure ventilation unit called High Efficiency Particulate Air (HEPA) filter to maintain aseptic condition.
• Culture facility: Growing the explant inoculated into culture tubes at 22-28° C with illumination of light 2400 lux, with a photoperiod of 8-16 hours and a relative humidity of about 60%.

Technique Involved in PTC

1. Sterilization:

Sterilization is the technique employed to get rid of microbes such as bacteria and fungi in the culture medium, vessels and explants.

(i) Maintenance of Aseptic Environment:

During in vitro tissue culture maintenance of aseptic environmental condition should be followed, i.e., sterilization of glassware, forceps, scalpels, and all accessories in wet steam sterilization by autoclaving at 15 psi (121°C) for 15 to 30 minutes or dipping in 70% ethanol followed by flming and cooling.

(ii) Sterilization of culture room:

Floor and walls are washed fist with detergent and then with 2% sodium hypochlorite or 95% ethanol. The cabinet of laminar airflow is sterilized by clearing the work surface with 95% ethanol and then exposure of UV radiation for 15 minutes.

(iii) Sterilization of Nutrient Media:

Culture media are dispensed in glass containers, plugged with non-absorbent cotton or sealed with plastic closures and then sterilized using autoclave at 15 psi (121°C) for 15 to 30 minutes. The plant extracts, vitamins, amino acids and hormones are sterilized by passing through Millipore filter with 0.2 mm pore diameter and then added to sterilized culture medium inside Laminar Airflow Chamber under sterile condition.

(iv) Sterilization of Explants:

The plant materials to be used for tissue culture should be surface sterilized by fist exposing the material in running tap water and then treating it in surface sterilization agents like 0.1% mercuric chloride, 70% ethanol under aseptic condition inside the Laminar Air Flow Chamber.

2. Media Preparation

The success of tissue culture lies in the composition of the growth medium, plant growth regulators and culture conditions such as temperature, pH, light and humidity. No single medium is capable of maintaining optimum growth of all plant tissues. Suitable nutrient medium as per the principle of tissue culture is prepared and used.

MS nutrient medium (Murashige and Skoog 1962) is commonly used. It has carbon sources, with suitable vitamins and hormones. The media formulations available for plant tissue culture other than MS are B5 medium (Gamborg.et.al 1968), White medium (white 1943), Nitsch’s medium (Nitsch & Nitsch 1969). A medium may be solid or semisolid or liquid. For solidifiation, a gelling agent such as agar is added.

3. Culture condition

pH

The pH of medium is normally adjusted between 5.6 to 6.0 for the best result.

Temperature

The cultures should be incubated normally at constant temperature of 25°C ± 2°C for optimal growth.

Humidity and Light Intensity

The cultures require 50-60% relative humidity and 16 hours of photoperiod by the illumination of cool white florescent tubes of approximately 1000 lux.

Aeration

Aeration to the culture can be provided by shaking the flasks or tubes of liquid culture on automatic shaker or aeration of the medium by passing with fiter-sterilized air.

4. Induction of Callus

Explant of 1-2 cm sterile segment selected from leaf, stem, tuber or root is inoculated (transferring the explants to sterile glass tube containing nutrient medium) in the MS nutrient medium supplemented with auxins and incubated at 25°C ± 2°C in an alternate light and dark period of 12 hours to induce cell division and soon the upper surface of explant develops into callus. Callus is a mass of unorganized growth of plant cells or tissues in in vitro culture medium.

5. Embryogenesis

The callus cells undergoes differentiation and produces somatic embryos, known as Embryoids. The embryoids are sub-cultured to produce plantlets.

6. Hardening

The planets developed in vitro require a hardening period and so are transferred to greenhouse or hardening chamber and then to normal environmental conditions.

Hardening is the gradual exposure of in vitro developed plantlets in humid chambers in diffused light for acclimatization so as to enable them to grow under normal field conditions.

Types of Plant tissue cultures

Based on the type of explants other plant tissue culture types are:-

1. Organ culture
2. Meristem culture
3. Protoplast culture
4. Cell suspension culture.

1. Organ culture:
The culture of embryos, anthers, ovaries, roots, shoots or other organs of plants on culture media.

2. Meristem Culture:
The culture of any plant meristematic tissue on culture media.

3. Protoplast Culture:
Protoplasts are cells without a cell wall, but bound by a cell membrane or plasma membrane.Using protoplasts, it is possible to regenerate whole plants from single cells and also develop somatic hybrids. Th steps involved in protoplast culture.

(i) Isolation of protoplast:
Small bits of plant tissue like leaf tissue are used for isolation of protoplast. The leaf tissue is immersed in 0.5% Macrozyme and 2% Onozuka cellulase enzymes dissolved in 13% sorbitol or mannitol at pH 5.4. It is then incubated over-night at 25°C.

After a gentle teasing of cells, protoplasts are obtained, and these are then transferred to 20% sucrose solution to retain their viability. They are then centrifuged to get pure protoplasts as different from debris of cell walls.

(ii) Fusion of protoplast:
It is done through the use of a suitable fusogen. This is normally PEG (Polyethylene Glycol). The isolated protoplast are incubated in 25 to 30% concentration of PEG with Ca++ ions and the protoplast shows agglutination (the formation of clumps of cells) and fusion.

(iii) Culture of protoplast:
MS liquid medium is used with some modifiation in droplet, plating or micro-drop array techniques. Protoplast viability is tested with florescein diacetate before the culture. The cultures are incubated in continuous light 1000-2000 lux at 25°C. The cell wall formation occurs within 24-48 hours and the first division of new cells occurs between 2-7 days of culture.

(iv) Selection of somatic hybrid cells:
The fusion product of protoplasts without nucleus of different cells is called a cybrid. Following this nuclear fusion take place. This process is called somatic hybridization.

4. Cell Suspension Culture

The growing of cells including the culture of single cells or small aggregates of cells in vitro in liquid medium is known as cell suspension culture. The cell suspension is prepared by transferring a portion of callus to the liquid medium and agitated using rotary shaker instrument. The cells are separated from the callus tissue and used for cell suspension culture.

Production of Secondary Metabolites

Cell suspension culture can be useful for the production of secondary metabolites like alkaloids, flvonoids, terpenoids, phenolic compounds and recombinant proteins. Secondary metabolites are chemical compounds that are not required by the plant for normal growth and development but are produced in the plant as ‘byproducts’ of cell metabolism. For Example: Biosynthesis and isolation of indole alkaloids from Catharanthus roseus plant cell culture.

The process of production of secondary metabolites can be scaled up and automated using bio-reactors for commercial production. Many strategies such as biotransformation, elicitation and immobilization have been used to make cell suspension cultures more efficient in the production of secondary metabolites. Few examples of industrially important plant secondary metabolites are listed below in the table: