PHYSIOLOGICAL ALTERATIONS INDUCED BY DROUGHT STRESS ON PRICKLY PEAR (Opuntia ficus-indica)

Abstract

Photochemical changes caused by drought stress in prickly pear cactus (Opuntia ficus-indica) have been little studied. In this research the effect of drought stress was analyzed in six months old potted plants grown in a greenhouse for 180 d. Under severe drought (without any watering) the chlorophyll concentration was significantly reduced. In chlorenchyma, chlorophyll a+b was diminished in 42.3 %, chlorophyll a in 34.1 %, and chlorophyll b in 31.4 %. In parenchyma, chlorophyll a+b, a and b were decreased in 39.4, 35.7 and 23.5 %, respectively. Phosphoenol pyruvate carboxylase activity was also significantly diminished (19.0 % in chlorenchyma and 60 % in parenchyma). Photosynthetic electron transport was diminished by 29.5 % in chlorenchyma, while it increased (150 %) in parenchyma. Under drought stress the chlorophyll fluorescence was reduced in both chlorenchyma and parenchyma. However under a moderate stress (two waterings) these physiological traits were only slightly affected.