Question

explain Plant adaptations to light, water, temperature, physical environments

Answer 1

Adaptations to light

1) Plants have different molecules to absorb light of different wavelengths for photosynthesis (Photosystem 1 and Photosystem 2 which contains chlorophylls and other accessory pigments).

2) Light-induced stomatal closure and opening to allow or inhibit transpiration.

3) Leaf size, color, variegation and plant height to get more light in dense forests is another adaptation in some plants.

4) Phototropism is a necessary adaptation in plants which make the plant shoot to grow in the direction of light.

5) Aquatic plants have floating leaves and that get direct sunlight to perform photosynthesis.

Adaptations to water

Plants have a vascular system (Xylem, phloem, roots) to absorb water from the ground. They are adapted to grow in the direction of water or away from water (Hydroptropism)

Plants have different adaptations to water according to their environment, for example, Xerophytes (desert plants) have longer roots, thick waxy cuticles, fleshy stems, flat or cylindrical stems containing chlorophylls. This prevents the loss of water from transpiration and helps in quick water absorption and storage of water in the fleshy stems. These are called succulent plants. The flowers can remain dormant for long times and bloom only when it rains.

Plants adapt to water stress by increased rooting, hydraulic conductance, reduced transpiration, the reduced surface area of transpiration. Underwater plants have a flexible structure to prevent damage from strong water currents. They lack a strong vascular system and absorb their nutrients, gases, and light directly from the water through the leaves.

Adaptations to temperature

Plants have adaptations to survive under high and low temperatures stress.

Plants thriving in hot climates have thermotolerance (e.g. Cacti). Their membrane lipids contain more amount of saturated fatty acids to maintain the fluidity and stability at high temperatures. They also have heat shock proteins. Other adaptations include vertical orientation of leaves, rolling off leaves to prevent transpiration, leaf hairs, waxy cuticle, smaller leaves. They have leaves with thin boundaries to increase heat loss.

Under extreme cold stress, plants respond to accumulating sugars, dehydrins to prevent ice crystal formation in cells. They synthesize proteins to stabilize the cell membrane. Certain genes regulating phytohormones and antifreeze proteins are expressed in cold stress-tolerant plants.

Adaptations to physical environments

To prevent physical damage due to weather and grazing animals plants have certain adaptations such as taste, thorns, hard shells, spines, thigmotropism, etc.

These adaptations discourage the animal from grazing by causing irritation, and allergic reaction and thus provide protection.

Thigmotropism is a directional response in some plants (Mimosa pudica, sweet pea plant) which allow them to close their leaves, curl tendrils upon some physical touch.  

Some plants can easily survive under high salinity by having the ability to break the salt to sodium and chloride ions.