Plant Growth And Development

Abscission is the separation of a leaf, fruit or other part from the body of a plant. It involves the formation of an abscission zone, at the base of the part within which a layer of cells (abscission layer) breaks down. This process is suppressed so long as sufficient amounts of auxin flow from the part through the abscission zone. However, if the auxin flow declines, for example, due to injury or ageing, abscission is activated and the part becomes separated.

Abscisic acid (ABA) is a naturally occurring plant growth substance that appears to be involved primarily in seed germination, stress responses and in regulating closure of stomata.

Day neutral plants can flower in all possible photoperiods. Such plants can blossom throughout the year, e.g., cucumber, cotton, sunflower, tomato, some varieties of pea, etc.

Auxanometer is used to measure the growth in length of a plant organ. There are two types of auxanometer-Arc auxanometer and Pfeffers auxanometer (Automatic auxanometer).

The correct answer is A:Gibberellin
Elongation of internode is caused by Gibberellin. Gibberellin is a class of hormone that helps in cell elongation. They promote the synthesis of
proteins that weakens the cell wall thus allowing them to grow.