Investigation of some physio-morphological traits of purslane (portulaca oleracea L.) landraces under drought stress

Purslane (Portulaca Oleracea L.) is a valuable medicinal plant growing in hot and dry conditions. Since drought stress is one of the most important factors limiting the production of agricultural products in these regions, this study aimed to evaluate the tolerance of different purslane landraces to drought stress in the greenhouse of Payame Noor University of Daregaz during the spring 2016. The experiment was as factorial based on completely randomized design with four levels of drought stress (field capacity, 75% FC, 50% FC and 25% FC), 5 landraces of purslane (Qom, Kalat, Sabzevar, Yazd, Gachsaran), and with three replications. The studied traits were relative water content, membrane sustainability index, photosynthetic pigment contents, chlorophyll sustainability index (the amount of chlorophylls and carotenoids), proline content, soluble carbohydrates, and fresh and dry weight of roots in two stages of vegetative and reproductive growth. Results showed that an increase in water stress level decreased the relative water content and cell membrane stability index while increasing the leaf chlorophyll index, carotenoid content, proline, and carbohydrates in different landraces of purslane. Results also indicated that the landraces of Gachsaran and Yazd had higher membrane stability index, lower RWC, and lower chlorophyll content under stress. Among the studied landraces, Qom and Kalat showed significant superiority compared to Sabzevar, Yazd and Gachsaran landraces in terms of proline and soluble carbohydrates. Also, the results showed that with increasing drought stress, fresh and dry weight of roots, leaves, and stems reduced at vegetative and generative stages of plant development such that the highest morphological and physiological traits in two stages of vegetative and reproductive growth were observed in 75% and 100% of field capacity and the minimum levels of these traits were obtained in 25% of field capacity. In general, Qom and Kalat landraces were more tolerant to drought stress compared to other landraces while Gachsaran, Yazd, and Sabzevar due to the relatively weak response to drought stress in most of the measured traits, were evaluated as susceptible landraces to drought stress.