Comparative growth and water relations of Cistus albidus and Cistus monspeliensis plants during water deficit conditions and recovery

Four month old Cistus albidus and Cistus monspeliensis plants growing in a growth chamber were submitted to two consecutive cycles. during which irrigation water was withheld for 7 days before being reconnected and the plants rewatered to run off (WD treatment). Control treatment plants were irrigated daily. At the end of the second dry period the treated plants were submitted to control plant conditions for 15 days. C. monspeliensis plants withstood the water deficit better than C. albidus, mainly due to its capacity to recover a water deficit situation. C. monspeliensis plants show net assimilation rate (NAR) levels above those of the control plants during the recovery period. In C. albidus the main growth limiting factor was the cellular expansion, whereas in C. monspeliensis photosynthesis was the limiting factor. Both species developed complementary avoidance mechanisms based on stomatal closure, a reduction in leaf area and root hydraulic conductivity, and epinasty. C. monspeliensis plants showed good osmotic adjustment in response to water deficit, which enabled it to avoid decreased leaf turgor potential and partial dehydration. After the water deficit, the mobilisation of accumulated organic solutes may also have contributed to the increased relative growth rate and NAR during the recovery period. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.