EFFECT OF DAMAGE DUE TO SIMULATED HAIL IN JURY IN DIFFERENT PHENOPHASES ON THE GROWTH AND DEVELOPMENT OF MAIZE

The aim of the experiments was to determine how a reduced leaf area of maize hit by hail during various phenophases in the vegetation period , influenced the growth, development and flowering time of the plants. The effect of various leaf injuries on plant height was found to be i nconsistent while the date of the injury was decisive. The plants were most sensitive to destructive effects damaging the leaf surface durin g the tasseling penophase. In earlier phenophases (4-, 8-leaf stages) damage to the whole of the above ground plant parts also reduced plant height. Plant height is generally of decisive importance in the case of male genotypes with shorter stalks, since it may limit the ability to provide pollen. The silking of plants defoliated at the beginning o f tasseling was considerably delayed compared with that of intact plan ts. In other words, pollination was restricted not only in space, but also in time, since asychronisation of flowering times was observed in the seed multiplication fields. Results corresponding to the literaty data (Pinter et al. 1977) were obtained as regards the assimilation a ctivity of the leaves. The role of the leaf next to the ear differed f rom one phenophase to the other and its outstanding importance was not confirmed. This was proved by grain yield data. All the treatments re duced the stalk diameter of the plants, the earlier the date of injury , the more severe this effect became. In future research the experimen ts will be extended to cover a wider range of genotypes.