comparative study of two pear cultivars to peg-induced osmotic stress

We studied the effect of polyethylene glycol (peg)-induced osmotic stress on pear cultivars (harrow sweet and bartlett) under in-vitro culture conditions. explants were cultured in ql medium containing 4% and 8% peg6000 using a factorial experiment based on completely randomized design. the medium without peg was considered as control. drought injury index, which was calculated based on morphological disorders, increased at 8% peg nearly to 2.00 and 1.50 units in cvs. bartlett and harrow sweet, respectively. owing to osmotic stress, the increase of malondialdehyde was accompanied with the reduction of cell membrane stability index in both cultivars. total phenolic components and antioxidant activity in leaves increased significantly in response to application of 4% and 8% peg. however, the severity of increase was higher in cv. harrow sweet. it was revealed that cv. harrow sweet had higher tolerance to osmotic stress than bartlett. moreover, the parameters related to oxidative damages and ros scavenging capacity were more descriminant against osmotic stress under in vitro system.