Déficit hídrico e ácido abscísico no crescimento, metabolismo fotossintético e antioxidante em mudas de Calophyllum brasiliense Cambess

Abstract

Plants submitted to water deficit conditions may present changes in morphological characteristics, which can guarantee their adaptability and survival to stress. In addition, the water deficit increases the concentration of abscisic acid (ABA), which triggers several responses in the plant. The objective of this study was to evaluate the intermittent water deficit in Calophyllum brasiliense Cambess. treated or not with abscisic acid, under morphophysiological, enzymatic and stomatal responses. The experiment was conducted in a greenhouse in a randomized design with six treatments: 1) daily irrigation without abscisic acid (ABA) (I 0 ABA); 2) daily irrigation + 10 μM ABA (I 10 ABA); 3) daily irrigation + 100 μM ABA (I 100 ABA); 4) suspension of daily irrigation without ABA (E 0 ABA); 5) daily irrigation suspension + 10 μM ABA (E 10 ABA); 6) suspension of daily irrigation + ABA 100 μM (E 100 ABA) and four replicates. The C. brasiliense seedlings submitted to the water deficit showed a reduction in gas exchange, leaf water potential, increased enzymatic activity, changes in biomass parameters such as stem diameter, chlorophyll index, root system growth, leaf area increase and stomatal density. The reduction of the stomatal conductance was accompanied by the photosynthetic and transpiratory rate, however, the seedlings receiving the 10 μM ABA dose maintained the photosynthetic rate higher than the other treatments of the water deficit. The influence of the 10 μM dose of ABA was also observed in the chlorophyll fluorescence where the seedlings that received that dose did not present a reduction in the efficiency of the photosynthetic apparatus. The activity of the antioxidant enzymes during the periods of water suspension varied according to the enzyme, dose of ABA and part of the plant. After reirrigation of the seedlings and until the end of the evaluations, all the physiological and enzymatic characteristics studied under water restriction recover. The water restriction triggered adaptive responses in Calophyllum brasiliense seedlings, as an increase in root growth and stomatal density. The application of 10 μM of ABA in the plants under water deficit stresses the effect and optimizes the recovery of the plants after reirrigation, maintaining the water balance and the relative water content in the leaf close to the control as well as the maintenance of the integrity and functioning of the photosynthetic apparatus . It was also observed that during the evaluation period the plants did not recover their growth and the stomatal aspects after the irrigation reestablishment.