Osmotic adjustment, proline accumulation and cell membrane stability in leaves of Cocos nucifera submitted to drought stress

The role of drought-induced prolme accumulation in coconut leaves is still unclear With the objective of evaluating the impact of water shortage on leaf osmotic potential, prolme accumulation and cell membrane stability in young plants of two Brazilian Green Dwarf coconut ecotypes from contrasting areas (Brazilian Green Dwarf from Una, Bahia, UGD, and from Jiqui. Rio Gi ande do Norte, JGD), a pot experiment was conducted under greenhouse conditions. Three drought cycles consisting of suspension of irrigation until the net photosynthetic rate (A) approached zero and rewatering until ecovery of A to 85% of the irrigated control plants Pre-dawn leaf water potential (psi(PD)) reached -1 2 MPa at the point of maximum stress (PMS) Dry matter production and leaf area were severely reduced by drought treatment in the two ecotypes Corrected values of osmotic potential were significantly reduced in stressed plants of the two ecotypes. Green dwarf coconut palm showed low osmotic adjustment (from 005 to 0.24 MPa) and significant accumulation of proline (from 1.5 to 2 1 times in relation to control) in leaflets in response to water deficit. Considering the growth reduction observed in both ecotypes, proline was not associated to osmoregulation On the other hand, the absence of membrane damage. as indicated by electrolyte leakage method, suggests that the protective role of praline in this specie can be more important The two ecotypes of Green dwarf coconut palm behaved similarly in the present experiment for most traits evaluated Slight differences among the ecotypes were observed with respect to the response to treatments, such as higher proline accumulation in JGD Crown Copyright (C) 2010 Published by Elsevier BV All rights reserved