नमस्कार मित्रांनो इयत्ता बारावी Biology या Subject च्या Practical मध्ये PART - B: Demonstration Experiments (Spotting) हा भाग Practical Exam च्या दृष्टीने फार महत्त्वाचा आहे. या Blog Post मध्ये आपण Spotting Practical Number 8: Study of plants found in xerophytic and aquatic conditions/habitats. And comment on their adaptations ह्या Practical Experiment चे Answer पाहणार आहोत. खाली दिलेल्या उत्तरांमध्ये काही अडचण असल्यास आम्हाला comment करा किंवा तुमच्या संबंधीत विषय शिक्षकांशी चर्चा करा.
B. DEMONSTRATION EXPERIMENTS (Spotting)
8. Study of plants found in xerophytic and aquatic conditions/habitats. And comment on their adaptations.
Introduction :-
• Adjustment (acclimatization) of plants and animals for their survival and perpetuation, to their environment by means of special structures or functions, is known as adaptation.
• The plants that can grow and survive in deserts, dry conditions of soil and high temperature, are called xerophytes.
• All xerophytes show adaptations to reduce the loss of water due to transpiration. Some xerophytes show the presence of stored mucilage in the plant parts that help in retaining water. Some plants have latex, that help retaining water and sealing the place of injury. e.g. Euphorbia, Calotropis, Acacia, Opuntia.
• The plants that grow in abundance of water are, called hydrophytes. They are generally adapted to remain buoyant and avoid decaying and tearing effects of water. They have developed arenchyma tissue for bouyancy. e.g. Hydrilla, Vallisneria, Eichhornia, Pistia, Nelumbo (Lotus), Typha.
1. Calotropis procera (Ruee) :-
Comments :
1. It is non-succulent, drought enduring, wild shrubs of arid, desert and waste lands.
2. The leaves and young branches are covered by a mealy coating along with hair which acts as an insulating covering.
3. The leaves are thick and somewhat leathery.
4. The plant possess latex.
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| Fig. Calotropis |
2. Acacia arabica (Babhool) :-
Comments :
1. It is a non-succulent xerophyte.
2. The leaves are bipinnately compound. Leaflets are very small in size to reduce transpiration.
3. The stipules are modified into spines to reduce transpiration and also to protect plants against marauding/ grazing animals.
4. The older parts of the stem are covered over by thick, brown bark.
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| Fig. Acacia arabica |
3. Opuntia dillenii (Nagphani) :-
Comments :
1. It is a succulent (drought resisting or enduring) xerophyte.
2. The stem is flattened, jointed, green and is called phylloclade. It takes over the function of photosynthesis because the leaves are modified into spines.
3. The stem i.e. phylloclade is fleshy succulent due to the presence of mucilage that retains water (water storage tissue).
4. Phylloclades are with many nodes (areoles) and internodes. The areoles have one or more spines which represent the modified leaves of the axillary branch.
5. Bristles (Trichomes) provide protection against grazing animals.
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| Fig. Opuntia |
4. Hydrilla :-
Comments :
1. It is a submerged hydrophyte i.e. grows entirely under water.
2. It is attached to the substratum by poorly developed adventitious roots in fresh water.
3. The stem is slender and soft. It is without mechanical tissue, hence it limps, when taken out of water.
4. Leaves are very thin, membranous and are arranged in whorls. They lack cuticles and stomata.
5. The entire plant is covered by mucilage that protects it from the rottening effect of water.
Vallisneria is another submerged hydrophyte.
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| Fig. Hydrilla |
5. Eichhornia (Water Hyacinth) :-
Comments :
1. It is a free floating hydrophyte that grows in fresh water ponds, lakes, etc.
2. The stem is short and spongy due to the aerenchyma that stores air. It is the offset that grows prostrate just below the water surface and serve as means for vegetative, reproduction.
3. Leaves show swollen, spongy, petioles and arise in clusters at nodes. They have a waxy coating in addition to the cuticle to prevent wetting and rottening.
4. Adventitious roots are also produced in clusters at nodes. They act as balancers. They have root pockets root hair is absent.
Pistia is another free floating hydrophyte, while Nelumbo (lotus) is an anchored or rooted hydrophyte with floating leaves.
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| Fig. Eichhornia |
6. Typha (Cattail) :-
Comments :
1. It is an amphibious and anchored hydrophyte which grows in marshy places or shallow waters.
2. The stem is rhizome with adventitious roots and emergent leaves, coming out of the water surface.
3. The leaves are long, linear, soft, spongy, thick and sub-cylindrical. They have aerenchyma tissue.
4. The leaves show the presence of mechanical tissue also and hence they are able to stand erect. They have cuticles and stomata on the emergent part.
(Actually Typha is a hygrophyte)
Questions
1. Enlist the morphological adaptations in xerophytic plants.
Ans :- 1. Thick, waxy cuticle to reduce water loss.
2. Reduced or modified leaves (e.g., spines) to minimize transpiration.
3. Deep or widespread root systems for efficient water absorption.
2. Write anatomical adaptations in desert plants.
Ans :- 1. Sunken stomata and fewer stomata to reduce water loss.
2. Thick-walled epidermal cells and a multilayered cuticle to prevent desiccation.
3. Well-developed parenchyma or water-storing tissues in stems and leaves for water storage.
3. Enlist the morphological adaptations in aquatic plants.
Ans :- 1. Presence of large air spaces (aerenchyma) in stems and leaves for buoyancy.
2. Thin, flexible stems and leaves to withstand water currents.
3. Reduced or absent cuticle and stomata for direct gas exchange with water.
4. Write anatomical adaptations in aquatic plants.
Ans :- 1. Aerenchyma tissues for buoyancy and efficient gas exchange.
2. Reduced vascular tissues as water is readily available.
3. Thin epidermis without a thick cuticle for easy absorption of water and nutrients.
5. Why petiole in the Eichhornica plant spongy?
Ans :- The petiole in the Eichhornia plant is spongy due to the presence of aerenchyma tissue. This adaptation provides buoyancy, allowing the plant to float on water. It also facilitates gas exchange in aquatic environments.
6. What are the advantages of leaves modified into spines in cactus plant.
Ans :- Leaves modified into spines in cactus reduce water loss by minimizing transpiration. They provide protection against herbivores. Additionally, spines help in shading the plant, reducing water evaporation in hot desert environments.
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