Aplicação de reguladores vegetais e de fosfito de potássio em mudas de eucalipto submetidas À deficiência hídrica

Abstract

The objective of this study was to evaluate the effects of plant growth regulators and potassium phosphite on hybrid seedlings of Eucalyptus grandis under water stress. The experiment was conducted using a completely randomized experimental design with nine treatments and four replicates in a greenhouse at the Center of Advanced Research in Weed Science in the Department of Plant Production and Breeding at the College of Agricultural Sciences, UNESP, Botucatu (SP). Each experimental plot consisted of a vase containing 5000 cm³ soil, in which a seedling was transplanted at 3-4 leaf stage. When plants were uniform and well acclimated, the treatments were sprayed on the leaves using 50 mL solution with the specific dose for each plant growth regulator and potassium phosphite. Each treatment consisted of 200 g ha^-1 salicylic acid, 200 g ha^-1 methyl salicylate, 1000 g ha^-1 jasmonic acid, 1000 g ha^-1 methyl jasmonate, 1000 g ha^-1 dihydro jasmonic acid, 1000 g ha^-1 methyl dihydro jasmonate, 5 L potassium phosphite and two control treatments, with no compound application, one under water stress and the other being irrigated. Irrigation was suspended seven days after treatment application. The following variables were analyzed: transpiration rate, electron transport rate (ETR) and content of lipoperoxides in the leaves. The results showed that water stress increased the levels of lipoperoxides and reduced ETR in the leaves of eucalyptus. However, application of plant growth regulators and potassium phosphite attenuated the effects of water stress in the plants, mostly in the treatments with salicylic acid and jasmonic acid and their methyl esters.