Evaluation of Physiological Responses of Tuberose (Polianthes tuberosa L.) to Water Deficit Stress

Water stress is one of the main factors of severe damage and limitation of plant production in Iran. The paper reports a pot experiment conducted by using a factorial experiment based on a completely randomized design with three replications (each replication composed of four pots) to compare the physiological and biochemical characteristics of two varieties of tuberose (double- and single-flower) for their tolerance to water stress. Three water stress levels, including no stress (W1 = 90% of FC), moderate stress (W2 = 75% of FC) and severe stress (W3 = 60% of FC), were applied throughout the experiment.Physiological traits including relative water content (RWC) and electrolyte leakage (EL) and biochemical traits including total chlorophyll (Chl), carotenoid (Car) contents, proline, malondialdehyde (MDA), antioxidant enzymes activity (SOD, APX, and CAT), photosynthesis rate (A), transpiration rate (E), and stomatal resistance (rs) were investigated. Results showed that the physiological and biochemical characteristics of the tuberose plants were highly affected by the application of water stress. MDA and EL showed a significant correlation with most physiological characteristics. Water stress caused significant increases in RWC, A, E, rs, Chl, APX, and SOD activities of the leaves of the single-flower cultivar. CAT, MDA, and proline content in the leaves of the double-flower cultivar were significantly higher than those in the leaves of the single-flower cultivar, regardless of water treatments. The results showed that the single-flower cultivar grew better than the double-flower one under stress conditions.