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 limits of plant production in Iran. In this research, a pot experiment was conducted by using a factorial experiment based on a completely randomized design; there were three replications (each replication contained four pots) to compare physiological and biochemical characteristics of two varieties of tuberose (double- and single- flower) for their tolerance to water stress. Three water stress levels, no stress (W1 = 90 % of FC), moderate stress (W2 = 75 % of FC) and severe stress (W3=60 % of FC), were maintained throughout the experiment.Physiological traits including relative water content (RWC) and electrolyte leakage (EL) were investigated and also were 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). Results showed that physiological and biochemical characteristics of 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 a significant increase of RWC, A, E, rs, Chl, APX, and SOD activities in leaves of single-flower cultivar. CAT, MDA, and proline content in leaves of double-flower cultivar were significantly higher than single-flower cultivar, regardless of water treatments. The results of this study showed that the single-flower cultivar grows better than the double-flower one under stress conditions.