Características fisiológicas de clones de seringueira (Hevea spp.) em função da disponibilidade de água no solo

Abstract

The objective of the present study was to verify metabolic changes related to carbon assimilation, antioxidant systems and osmolyte production in young plants of four rubber tree clones (GT1, IAC40, PR255 and RRIM600) submitted to progressive soil water deficit 32 days of water suspension (32 DIS). After this period of water suspension, the soil was rehydrated for 15 days (15 DRS). Evaluations were made at 32 DIS and 15 DRS for gas exchange and biochemical analyzes. The water potential was evaluated at 0, 16 and 32 days after the imposition of the water deficit and at 15 days after irrigation. Relative water content (RWC), water potential (Ψw), gas exchange, chlorophyll fluorescence, carbon metabolism and antioxidants as well as proline and glycine betaine were evaluated. The decrease of Ψw led to decreases in A, gs, and E. In relation to the internal carbon (Ci) only PR255 plants did not distinguish from the control, other clones reduced their internal carbon contents under water deficit. However, a recovery of these values was observed for all clones after 15 DRS. The A / Ci and US ratios were affected by water suppression, generally with increased water use efficiency in clones and A / Ci reduction. The photochemical process was altered under water deficit. At 32 DIS, a lower accumulation of dry leaf mass was observed for all the clones. An increase in the content of AST and AR and amino acids was observed for all clones in 32 DIS. In relation to total proteins, starch IAPC, INC and SUSY, a decrease occurred in all the clones at 32 DIS and after the restoration of the irrigation, no differences were observed compared to irrigated plants with the exception of the GT1 clone that did not differ in the activity of the SPS enzyme. The water deficit stimulated the enzymatic antioxidant system, the enzymes; SOD, CAT and APX in general had their activities increased with the return of values in 15 DRS in which the activity of the antioxidant enzymes remained similar to the control. In this study, an increase was observed in H2O2 contents under water deficit, in which, after restoration of irrigation, RRIM600, IAC40 and PR255 clones continued with higher levels compared to control. The levels of lipid peroxidation (MDA), reached higher levels due to the low water availability. The water deficiency promoted an accumulation in the contents of PRO and GB and as in the other characteristics, after the rehydration of the substrate these contents were similar to their respective controls. Clones GT1, IAC40 and RRIM600 showed superiority to clone PR255 in terms of stability and efficiency in the use of energy and antioxidant activity and accumulation of organic osmolytes under conditions of low availability of water. It is suggested that the clones GT1, IAC 40 and RRIM 600 are more tolerant to water stress and more suitable for non-traditional areas of rubber tree plantations that present summer or irregular distribution of rainfall.