Ecological Adaptation ppt.pptx

“Any characteristic of an organism or its part which enable it to survive in its own particular habitat is called adaptation”. It is also defined as, “Adaptation is the evolutionary process whereby an organism becomes able to survive and reproduce in its habitat or habitats”. Adaptation is nothing but any changes in the structure or function of an organism or in any parts of its that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment.

1. B.Sc. I, Sem. II, Paper III PLANT ECOLOGY Associate Professor, Dr. S. A. Gaikwad Dept. of Botany Vidnyan Mahavidyalaya , Sangola

2. Ecological adaptation Adaptations in an organism or in the community are generally for the changes in the entire environment. The organisms adapt to the changes in the surrounding atmosphere because of the basic property of the protoplasm, known as the adaptability. The adaptability helps the organisms to remain in the process of evolution. The ecological adaptations are the responses shown by the plants to the environmental conditions and they are the adjustments as per environmental changes. “The changes in the characters, which enable the organisms to withstand the changes in the surrounding environment and to make use of these changes for the maximum benefits, are known as adaptations.” The adaptations which are induced by water factor or availability of water in the environment are of three types – xeric, hydric and mesic. These terms are used for the environmental conditions which are responsible for respective adaptations.

3. Ecological adaptation All adaptations may be structural, physiological or behavioral, are the result of evolution, which is a change in a species over thousands of years or within a few lifetimes. The life cycle of any organism is controlled by number of environmental factors. Water is the most essential factor for every living organism. Plants growing under different environmental conditions exhibit various adaptation. For the first time, Warming (1895) had realized the impact of different factors upon the vegetation in ecology and he classified plants on the basis of nature of substratum on which they grow. Later on, Warming (1909) classified the plants on the basis of their water requirements. The plants are divided into three major groups as per their water requirements- 1. Hydrophytes- Plants growing in abundant water i.e., in maximum water supply and near the water, 2. Xerophytes- Plants growing in dry, arid region which shows shortage of water in the soil i.e., in minimum supply of water, 3. Mesophytes - Plants growing in habitat with neither less nor more water is available i.e., moderate water supply is required.

4. Ecological adaptation - Hydric adaptation Plants are either growing on land or in water. The land plants get essential water from the soil but the aquatic plants are growing within or near the water. On the basis of availability of water, the adaptations are of three types – Xeric, Hydric and Mesic. Hydric Adaptations: Water availability is far more than the requirement of plants. There is no need of mechanical strengthening as plants are supported by water all around them. Aquatic plants can only grow partially or completely in water or in soil that is permanently saturated with water. The habitat of aquatic plants is either fresh water or marine. Underwater leaves and stems are flexible to move with water currents. As the plants are growing in hydric conditions these are known as hydrophytes (Hydro- water, phytes -plants). There are three different types of hydrophytes -

5. Ecological adaptation- Hydric adaptation As the plants are growing in hydric conditions these are known as hydrophytes (Hydro- water, phytes -plants). There are three different types of hydrophytes - a. Submerged hydrophytes- Plants are b. Floating hydrophytes – These are of two types growing under the water surface 1. Free floating hydrophytes: Freely floats on the water e.g., Hydrilla, Potamogeton , Utricularia surface, not rooted in the soil e.g., Eichhornia, Pistia .

6. Ecological adaptation- Hydric adaptation 2. Floating but rooted hydrophytes: Plants are rooted in the soil but leaves are floating on the surface of water e.g. Nymphaea, Marsilea. c. Amphibious hydrophytes - These are growing in shallow water or in muddy soil i.e., in marshy places e.g. Cyperus , Typha All these hydrophytes have certain morphological, anatomical and physiological modifications while growing in above aquatic conditions. These modifications are known as hydrophytic adaptations which are discussed below-

7. Ecological adaptation- Hydric adaptation

8. Ecological adaptation- Hydric adaptation Roots: Root system of hydrophytes is not of much importance, because they grow partially or completely in water. Roots are poorly developed (e.g., Hydrilla, Vallisneria .), reduced or completely absent (e.g., Utricularia, Ceratophyllum ,). However, some hydrophytes have well developed adventitious roots (e.g., Eichhornia, Pistia ). Root caps usually absent. Root hairs are poorly developed in most hydrophytes. Root tips are often provided with root pockets (e.g., Eichhornia). Stem: In submerged hydrophytes, the stem is long, slender thin, spongy and flexible e.g., Hydrilla . In free floating hydrophytes, the stem or stolon is horizontal, spongy , thick and short, floating on the surface of water e.g., Eichhornia, Azolla, Pistia while in rooted hydrophytes like Nymphaea, Nelumbium , Cyperus , the stem is a rhi­zome. These rhizomes live for many years and produce leaves every year. Mucilaginous or waxy coating is present on entire plant body. Morphological(External)adaptations of Hydrophytes:

9. Ecological adaptation- Hydric adaptation Morphological adaptations of Hydrophytes: Petioles : Some floating hydrophytes show special features in the petioles. In free floating but rooted hydrophytes like Nymphaea and Nelumbium , petioles are long, slender and spongy while they are swollen, spongy in free floating hydrophyte like Eichhornia, helps in floating. Leaves: The leaves are thin, long or ribbon like (e.g., Vallisnaria ). linear (e.g., Potamogaton ) or finally dissected (e.g., Ceratophyllum ). The leaves may be long, flat, and entire as in Nelumbo, Nymphaea . The petioles are long swollen and spongy (e.g., Eichhornia, Trapa ). Heterophylly is observed in some plants. Generally, the leaves are reduced in thickness and covered by waxy coating.

10. Anatomical (Internal) adaptations of Hydrophytes: Leaves: Root: Cuticle is very thin or absent. Root hairs present in amphibious hydrophytes. Epidermis is single layered made up of thin-walled cells. Parenchymatous cortex i.e., arenchyma is well developed. It has numerous air chambers which help in buoyancy (floating) and rapid gaseous exchange. Conducting tissues, i.e., xylem and phloem, developed poorly and less differentiated. Only xylem tracheids are present in submerged forms while phloem is well differentiated in amphibious hydrophytes. Mechanical tissues are generally absent. Pith is absent. Cuticle is absent or poorly developed in Nymphaea leaves . Epidermis is single layered with thin walled parenchymatous cells. Chlorophyll found in all the tissues. Epidermal cells of leaves contain abundant chloroplasts and they can function as photosynthetic tissue, especially where the leaves and stems are very thin e.g., Hydrilla. Stomata are totally absent in submerged plants, but in floating leaves, stomata are present on the upper surface. In amphibious plants stomata may be scattered on all the aerial parts. In submerged plants, mesophyll tissues are not differentiated while in other forms of hydrophytes these are well differentiated into spongy parenchyma and palisade tissues. They show air cavities. In submerged leaves, air chambers are filled with respiratory and other gases. Mucilage canals and mucilage cells are present which secrete mucilage to protect the plant body. Mechanical tissues are poorly developed or completely absent.

11. Ecological adaptation- Hydric adaptation Anatomical (Internal) adaptations of Hydrophytes: Stem: Cuticle is very thin, poorly developed or absent. Epidermis is single layered with thin walled parenchymatous cells. The rhizome of Nymphaea and stem of Typha shows well developed epidermis. In floating forms, thin walled parenchymatous or collenchymatous hypodermis is present which is containing chloroplasts. Parenchymatous cortex is well developed with number of air chambers which help in buoyancy (floating) and rapid gaseous exchange. Endodermis and pericycle is generally distinct. The vascular tissues, i.e., xylem and phloem, developed poorly, thin walled except in amphibious hydrophytes. Mechanical tissues are poorly developed or absent.

12. Ecological adaptation- Hydric adaptation Physiological Adaptations  of Hydrophytes: Osmotic concentrations of cell sap are low. Entire plant surface absorbs water and nutrients. Hydrophytes maintain active photosynthesis as chloroplasts are distributed throughout the plant body. CO 2 and O 2 evolved during respiration and photosynthesis is stored in air chambers for future use. No transpiration from submerged plants.

13. Ecological adaptation- Xeric adaptation As the plants are growing in xeric conditions these are known as xerophytes. There are three different types of xerophytes - Drought escaping plants (Ephemerals) - These are also called as drought evaders which have a very short life cycle i.e., they are annuals, to avoid the drought e.g. Tribulus terrestris , Argemone mexicana , Cassia tora etc. b. Drought tolerant/enduring plants (succulents) - They store large amount of water in different organs of their body, so they become fleshy. They are called succulents. The stem succulents store water in stem so it becomes fleshy, green and photosynthetic leaves are reduced to spines e. g. Opuntia. In leaf succulents store water in leaves and they become thick fleshy as in Aloe, Portulaca. Water availability in the soil is very low than the requirement of plants. The temperature is very high so humidity is less which results in the loss of water. Arid, dry area with low rainfall, Hot, dry climate is responsible for increasing evaporation and transpiration. All these environmental conditions are responsible for drought in that habitat

14. Ecological adaptation- Xeric adaptation c. Drought resisting plants (Non- succulents) - These plants are the true xerophytes. They resist the drought by showing external and internal adaptations to dry conditions. Examples are Calotropis, Casuarina, Nerium, Acacia.

15. Ecological adaptation- Xeric adaptation Stem: The stem is hard, woody either aerial or subterranean, sometimes covered with wax e.g., Equisetum . Stem may be covered with dense hairs as in Calotropis or thorns. In some succulents, it is bulbous and fleshy. The extreme xerophytes like Opuntia, stem is modified into leaf like, flattened fleshy structure known as phylloclade while in Asparagus it is modified into small needle-like green structures exactly looking like leaves called as cladodes. Both phylloclade and cladodes perform the function of leaf i.e., photosynthesis. Morphological adaptations of xerophytes: Root: Root system is well developed and profusely branched. The roots of perennial xerophytes grow deep into the ground that can penetrate several meters down where plenty of water is available. Most of the desert plants like Cacti develop superficial and shallow root system which is able to absorb water that is available near the surface of the earth .

16. Morphological adaptations of xerophytes: Ecological adaptation- Xeric adaptation Leaves: Leaves are thick and leathery, tough, shining ( Nerium ) or may be thick, fleshy & succulent ( Aloe ). In some plants like Cacti, leaves are reduced, usually small and fall off during prolonged dry conditions to prevent water loss by simply losing their leaves, absent or modified into spines ( Zizyphus , Capparis, Acacia ). Leaf lamina may be long, narrow needle like as in Pinus or divided into many leaflets like Acacia , leaf apex & margin is spiny ( Aloe ). Curled leaves are present in some extreme xerophytic grasses. The rolling or folding of leaves minimizing the evaporation and water loss.

17. Ecological adaptation- Xeric adaptation Succulent Xerophyte- Aloe b) Non succulent xerophyte- Ziziphus

18. Anatomical adaptations of xerophytes: Ecological adaptation- Xeric adaptation Roots: Root cap is present. Root hairs are large in number. Conducting tissues, i.e., xylem and phloem, developed very well. Thick cuticle is present which protects internal tissues from dry and hot soils. Stem: Epidermis is thick walled and lignified. Some plants show wax deposition on the surface of epidermis and even in the hypodermis. In succulent stems, thin walled parenchymatous cells store excess amount of water, mucilage, latex, etc. called water storage tissues. Woody xerophytes produce very well-developed cork in the stem . Mechanical tissues and vascular tissues are well developed.

19. Anatomical adaptations of xerophytes: Ecological adaptation- Xeric adaptation Leaves: Epidermis with thick cuticle & epidermal cells are thick walled. Multilayered epidermis is present on both upper and lower surface of leaves. Sunken stomata are present and stomatal opening is covered with number of hairs, presence of many layered palisade tissue. Mesophyll is very compact with reduced intercellular spaces. In succulent leaves, spongy parenchyma i.e., water storage tissue stores water. Thick-walled sclerenchyma cells are seen in the hypodermis e.g., Pinus needle. Well-developed vascular and mechanical tissues are present.

20. Ecological adaptation- Xeric adaptation Physiological Adaptations  of Xerophytes: The stomata of these plants open during night hours and remain closed during the day to prevent water loss by reducing evaporation rate. The xerophytes have very high osmotic pressure of the cell sap , which increases the turgidity of the cell sap. These plants control the excessive loss of water during transpiration by reducing total transpiring surface, Xerophytes have greater potentiality to resist wilting. The protoplasm in these plants is less viscous and more permeable and resistant to heat. These plants may secrete resins and waxes ( epicuticular wax ) on their surfaces, which reduce evaporation.