DROUGHT RESPONSE OF YOUNG APPLE-TREES ON 3 ROOTSTOCKS - GROWTH AND DEVELOPMENT

'Imperial Gala' apple (Mains domestica Borkh,) trees, trained to two s hoots, on M.9 EMLA, MM.111, and Mark rootstocks were subjected to two drought-stress and recovery periods in a rainshelter. Leaf growth rate , leaf area, leaf emergence, shoot length, and trunk cross-sectional a rea were measured during each stress and recovery period, Leaf growth rate was reduced during both stress periods but most consistently duri ng the second drought stress. Length of the less-vigorous shoot was re duced most consistently due to drought stress hut did not recover upon irrigation, Leaf emergence and trunk cross-sectional area increment w ere inconsistent in response to stress. Tree growth was reduced by dro ught stress to the greatest extent for trees on Mark, with MM.111 inte rmediate and M.9 EMLA least affected. At termination, the plants were separated into roots, current-season shoot growth, previous-season sho ot growth, and rootstock, and dry weights were measured, Dry weights c onfirmed the growth measurements taken during the experiment with a 16 %, 27%, and 34% reduction in total plant dry weight for drought-stress ed trees on M.9 EMLA, MM.111, and Mark, respectively, compared to corr esponding controls, It was concluded that Mark was the most sensitive of the three rootstocks followed by MM.111; M.9 EMLA was the most drou ght resistant.