Abscisic acid in the ear of winter wheat: Transport from the roots, the leaves, or biosynthesis in situ?

Abstract

The role of abscisic acid (ABA) in the formation of yields of winter wheat was studied from the following points of view: transport of ¹⁴C-ABA from the flag leaf to the other parts of plant in the period prior to anthesis, effect of ABA and cytokinins on the transport of ¹⁴C-sucrose to the kernels, and endogenous level of (+)-S-ABA in the flag leaf and in the ear before and after anthesis. Experiments revealed that the transport of ¹⁴C-ABA from the flag leaf is directed to the internode and the ear. The application of ABA inhibited the transport of ¹⁴C-sucrose from the nutrient solution to the developing kernels simultaneously with the number of kernels. The interactions between ABA and cytokinins in the period prior to anthesis could be related to the effects on the respiration system which could consequently influence the transport of assimilates towards sink tissues and play an important role in yield formation. The endogenous level of ABA in the ear corresponded with its level in the flag leaf up to the period of kernel maturation: from this point the level sharply rose in the leaf whilst in kernels it started to decrease. The results indicate that the flag leaf could be a more important source of ABA than the roots and that ABA synthesised there could be easily transported to the developing ear.