Study of in vitro drought stress on the response of some genotypes of Damask rose relying on water relations

Damask rose is one of the oldest and most valuable rose varieties that to some extent, tolerates water deficiency. However, the selection and identification of genotypes that are more tolerant to drought stress will be effective in development of cultivation of the plant. In this case, an experiment was performed under in vitro conditions using polyethylene glycol at five levels (0, 25, 50, 75 and 100 g L-1) on four genotypes of Damask rose (Maragheh, Urmia, Pakdasht and Kashan) and the tolerance of genotypes to drought stress was measured based on water relations traits of the plant via response surface method (RSM). Results showed that as the severity of drought stress increased, the percentage of dry matter was increased in genotypes of Maragheh, Urmia and Kashan compared to the control. At concentration of 100 g L-1 PEG, Maragheh genotype had the highest fresh and dry weight, total chlorophyll, chl a and chl b and the lowest leaf number and height compared to the other genotypes. Carotenoid contents in Urmia and Maragheh genotypes were higher in 100 g L-1 PEG than other genotypes. As water deficiency increased, leaf water content in Maragheh, Kashan and Urmia genotypes decreased. Maragheh genotype with high values ​​of relative leaf water content, on the other hand, with a decrease in water moisture reduction, relative water loss and saturated water deficiency, showed a better protection mechanism against drought stress than the other three genotypes. After Maragheh genotype, Pakdasht genotype was partially resistance to drought stress up to 75 g L-1 polyethylene glycol.