Functional leaf responses of young Hevea brasiliensis plants subjected to water deficiency and rewatering

Hydric deficit is considered a factor that produces significant damage during the establishment and growth period of plantations. The goal of this study was to investigate morphophysiological and biochemical traits of leaves of the rubber seedlings in response to water deficiency and subsequent rewatering. Young Hevea brasiliensis plants of the RRIM 600 clone - Rubber Research Institute of Malaysia were divided into two treatments: treatment 1= irrigated plants (IR) and treatment 2= non-irrigated plants (NI). In these plants the photosynthesis (A) was monitored throughout the experimental period (0, 10, 25, 32, 38, 46, 54 and 68 days). The water potential in leaves (ψ_w) was determined using a Scholander pressure chamber. The photosynthesis (A), conductance (gs), transpiration (E) were determined using an infrared gas analyzer (LI-6400XT, LI-COR, Lincoln, Nebraska, USA) and leaf carbohydrates and proline content were determined by spectrophotometry (Amersham Biosciences Ultrospec 3100 pro). The ψ_w, A, gs, E and leaf starch content in treatment NI were reduced during the first 32 days, where A reached value close to 0 µmol m^-2s^-1. However, there was an increase in the concentration of total soluble sugar and proline during the same period. The recovery of photosynthesis (NI) occurred at 22 days after the rewatering when compared to irrigated plants (IR). Therefore, it can be concluded that the RRIM 600 clone has water stress tolerance in terms of how to deal with the progressive water stress, but the recovery from stress was relatively slow.

Keywords:
Carbohydrates; Growth; Stress; Gas exchange