ENDOGENOUS INDOLEACETIC AND ABSCISIC ACIDS IN LEAVES AND REPRODUCTIVE-ORGANS AT THE LATE STAGES OF PLANT DEVELOPMENT

The content of endogenous indoleacetic acid (IAA) and abscisic acid (A BA) in the source leaves and reproductive organs of wheat (Triticum ae stivum L.) and cucumber (Cucumis sativus L.) during their growth and d evelopment was determined, High content of IAA in wheat leaves during vegetative development and its decrease by earing and caryopsis format ion were demonstrated. Wheat defoliation (only the flag leaf remained) and cucumber decapitation (the shoot apex was removed) decreased IAA content in the leaves, in these plants, an inhibition of assimilate ex port from the leaf and its senescence were observed. ABA content in th e leaf increased by the earing stage. In the ear, ABA content reached its greatest value at milky ripeness, but dropped again at wax ripenes s. The removal of half an ear favored ABA accumulation in the remainin g half. The greatest ABA content in cucumber fruits was recorded two w eeks after pollination, which correlated with the highest rate of biom ass production. A conclusion about IAA regulation of leaf source activ ity and ABA regulation of ear sink activity is drawn.