Abscission, Fruit

Abscission, Fruit 

the separation of fruit from a branch caused by the formation of a separation layer of cells on the fruit stalk. It is also associated with the depletion of auxins by the fruit. The substance bonding the cells of the separation layer dissolves, and the cells separate from each other. At this stage of the process, the fruit is attached to the plant only by a vascular bundle. The wind and the force of gravity cause this bond to break, and the fruit falls. A fruit abscises soon after it sets. This is primarily because the plant cannot provide all of the developing fruits with the necessary amount of nutritive substances, and, as a result, those fruits that do not receive sufficient nourishment fall.

The premature abscission of fruit is often observed. The fruit abscises during infructescence and during the development of the germ. Premature abscission occurs as a result of damage by insects (primarily larvae of the codling moth) or by disease, low temperature, drought, and other unfavorable conditions. The principal method of combatting premature falling is the observance of a whole group of agricultural measures. Apple and pear trees should be sprayed with a weak auxin solution to delay the formation of the separation layer. To prevent the mass falling of cotton settings, the top of the main shoot is broken off and the branches growing on the lower part of the shrub are removed.