Explain the role of phytohormones in parthenocarpy and weed control



(a) Parthenocarpy : (i) The application of auxins and gibberellins on unpollinated flowers results in the production of seedless fruits.
(ii) It has been of great significance in such fruits where the number of seeds is very high and the seeds are of little food value (e.g., tomato, brinjal, guava, papaya, watermelon, orange) or the seeds are large in size (e.g., Litchi and Mango).
(iii) Natural parthenocarpy in banana and grapes is because their seedless varieties have higher content of endogenous auxins.
(b) Weed control: (i) Unwanted wild plants grow in a cultivated crop.
(ii) They interfere with the physiology of the crop. 2, 4-D and 2, 4, 5-T (Trichlorophenoxy acetic acid) are specific killers of dicot herbs and are known herbicides.
(iii) Thus in a field having monocot crop dicot weeds may be eradicated by spraying either 2, 4-D or 2,4,5-T.
(iv) These weedicides penetrate the meristematic tissues of the plant and inhibit cell division.
(v) They also affect metabolic activities resulting the death of the plant.