Zoology Test Paper

 Majorly the intensity of light regulates the temperature.

By utilizing capillary action and the inherent surface tension of water, transpiration pull and cohesion force transport the water by xylem in tall trees.

Sir J.C. Bose (1923) advocated pulsation theory to explain ascent of sap. He proved that the living cells of innermost layer of cortex lying just outside the endodermis were in a state of rhythmic pulsations.

Guttation is the secretion of water, during conditions of high humidity, on to the surface of leaves through specialized pores, or hydathodes. 

Guard cells contain chloroplasts to manufacture the food by photosynthesis, but epidermal cells lack chloroplasts.

Due to the hypertonic nature of salt. Any living cell in such an environment will become plasmolysed (loss of water) and die or become temporarily inactivated.

Transpiration primarily occurs through the stomata, which are located in the epidermis of the leaves. The epidermis is a type of dermal tissue, making it the site of maximum water loss.

The cohesion-tension theory, which combines the cohesive properties of water molecules and the pull created by transpiration in the leaves, is the main mechanism for transporting water to the tops of tall trees.

The transpiration pull and cohesion theory (Cohesion-Tension theory) is the most widely accepted explanation for the ascent of sap because it accounts for the physical forces needed to move water over great heights.

Guttation is the process by which plants lose water in the form of liquid droplets through specialized pores called hydathodes, typically occurring under conditions of high humidity and low transpiration.

Root hairs are found only in the zone of maturation, and not the zone of elongation, possibly because any root hairs that arise are sheared off as the root elongates and moves through the soil.

In cactus, stomata close at night to reduce water loss. They lose water when it is open so they open in the day when CO₂ is at its best.

Plasmodesmata are microscopic channels that traverse the cell walls of plant cells enabling the transport and communication between the cells.

An increase in CO2 concentration in the leaf's micro-environment generally triggers the closure of stomata. This response helps the plant conserve water when CO2 levels are sufficient for photosynthesis.

The conversion of starch into organic acids like malate increases the solute concentration in guard cells. This lowers the water potential, causing water to enter the cells and the stomata to open.

 When the cell is fully turgid then the diffusion pressure deficit (DPD) becomes zero to avoid the furthur absorption of water by the cell.

The plant cell is placed in a hypertonic solution, through which plant cell loses water and make the plant cell flaccid and causes the plasmolysis.

The solution having high solute concenteration is known as hypertonic solution.

If the anthocyanin pigments do not leak out of the beet root cells into the cold water, it demonstrates that the plasma membrane is impermeable to these molecules under those specific conditions.

Levitt (1974) postulate the theory of active potassium ion (<span style="font-family:" arial;="" font-size:="" small;="">K<sup style="font-family:" arial;="">+) transport mechanism <span style="font-family:" arial;="" font-size:="" small;="">for opening and closing of stomata.

Osmotic pressure is a colligative property that increases with the concentration of solutes. Since pure solvent has an osmotic pressure of zero, any solution containing solutes will have a greater osmotic pressure.

If a piece of potato tuber is placed in a concentrated sugar solution, it will become limp due to exosmosis (water moves out of the cell).

The synthesis of organic acids from starch in guard cells is a key step in stomatal opening. It leads to an influx of potassium ions and water, increasing the turgidity of the guard cells.

Transpiration causes evaporative cooling as water changes from liquid to vapor on the leaf surface. This process absorbs latent heat from the plant, effectively lowering its temperature.

Ascent of sap is the upward movement of water from the root to the crown. This movement is caused by the attraction of water molecules, i.e. cohesion force.