INTERACTION OF CYTOKININS AND ABSCISIC-AC ID IN WINTER-WHEAT IN THE PERIOD PRIOR TO ANTHESIS

The effect of N6-(m-hydroxybenzyl) adenosine (HBA) on the transport an d distribution of flag-leaf-applied C-14-ABA in winter wheat Kosutka a nd Branka in the period prior to anthesis was followed as well as the effect of HBA and inhibitor of ABA biosynthesis - fluridone on the tra nsport and distribution of C-14-sucrose (applied throughout the whole experiments in week intervals) and some yield components as the number and mass of kernels. The distribution of radioactivity after the C-14 -ABA application suggested, that the transport of ABA into the ear und er the effect of 10(-5) mol.l-1 HBA was inversely related to the numbe r of kernels and their mass: in the cv. Kosutka the transport of C-14- ABA was stimulated (Fig. 1), whilst the number of kernels in the ear w as found to be lower (Fig. 5). In the cultivar Branka the transport of C-14-ABA was inhibited by HBA application (Fig. 2), but the number of kernels and their mass was higher in this cultivar (Figs 5 and 6). Th e transport of C-14-sucrose into the kernels was influenced by the app lication of HBA more in the Branka cv. (i.e. cv. where the effect of H BA on the number and mass of kernels was more expressive) than in the cv. Kosutka (Figs 3 and 4). The results suggest that in cultivars with a different number of kernels the exogenous application of cytokinins could influence the transport of ABA in a different manner and the in crease of the transport of ABA into the ear in the pre-anthesis period could influence the total (final) number of kernels. The data on the effect of HBA on the transport of C-14-sucrose correspond with earlier findings (e.g. Borkovec, Prochazka, 1992) regarding the relation of n umber and mass and the effect of cytokinins on these traits in the per iod prior to anthesis.