Question

which plant hormone is responsible for the wilting and falling of leaves?

Answer 1

ANSWER
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THE PLANT _____ABSCISIC ACID ________HARMONE IS RESPONSIBLE FOR THE FALLING OF LEAVES

Answer 2

Answer:

Abscisic Acid (ABA) is the plant hormone responsible for the wilting and falling of leaves.

Explanation:

• Wilting may be defined as the drooping of leaves due to loss of turgidity.
• This occurs when transpiration exceeds the amount of water absorbed by the plants.

• On bright warm days when the rate of transpiration exceeds the absorption, creating water deficiency in the cells of the leaf. Thus, there is a partial loss of turgidity that does not cause visible wilting. Such a process is called incipient wilting.

• In dry and hot summer afternoons, the leaves wilt due to a high rate of transpiration, causing a loss of turgor. The wilted leaves and twigs recover at night when water absorption becomes more than transpiration. This is called temporary wilting.
• Sometimes, the amount of available soil water is so low that it is not available to the plants. At this stage, there is a general loss of turgidity and plants do not recover even after watering. This condition is referred to as permanent wilting.
• Even though the plant has wilted permanently, there is still some amount of water left in the soil.

• The percentage of water left in the soil when plants wilt permanently is called wilting coefficient or the permanent wilting percentage of the soil. It varies with different kinds of soils.

• Thus, wilting in the case of leaf occurs when the turgor pressure of leaf cells falls towards zero due to which plant will lose the turgidity and rigidity.
• This loss in turgidity leads to droop down of leaves and ultimately the leaves fall off.
• In leaves, the rate of transpiration occurs at a faster rate as compared to the rate at which water is absorbed.

• Therefore, the stress hormone Abscisic acid (ABA) is produced in the leaves.

• This helps in the closing of stomata by causing $K^{+}$ ions to leave the guard cells (thus reducing their turgidity) during periods of water shortage or drought and is involved in the wilting and falling to minimize the surface area for transpiration.

Thus it is the ABA or Abscisic acid that causes wilting and falling of leaves.

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