A study of physiological and antioxidant responses in Alcea rosea under drought stress during two phenological stages

In order to investigate the effect of drought stress on physiological responses of Alcea rosea plant in greenhouse at two growth stages, a factorial experiment was conducted in a completely randomized design with three replications. The experiment factors included two ecotypes (Mashhad and Tehran), five moisture levels (80 (control), 70, 60, 50 and 40% Field Capacity) at two growth stages (seedling and elongation stem). After applying drought stress at two growth stages, SPAD, electrolyte leakage, relative water content, proline, malondialdehyde, enzymes activity of leaf and total dry weight were measured. The highest relative content of leaf water (88.2%), total dry weight (36 g), and the lowest electrolyte leakage (6.23%) were recorded in Mashhad ecotype under 80% FC treatment at stage of stem elongation. In both ecotype, with increasing drought stress, the amount of proline had a rising trend at two stages. Also, the highest amount was recorded in ecotype Mashhad under 40% FC treatment at stage of stem elongation. In both ecotypes, the highest activity of malondialdehyde was observed in 40% FC treatment at seedling stage (11.9 and 11.4 nmol g-1 FW, respectively). In the ecotype of Mashhad and Tehran, with increasing drought stress from 80 to 40% FC at stage of stem elongation, the activity of the superoxide dismutase enzyme increased, from 49.9 to 1.98, and 1.91 U mg protein, respectively. The activity of ascorbate- peroxidase increased, when plants were under severe drought stress. There was a positive and significant correlation between chlorophyll index and relative water content with total dry weight of the plant. The results of this experiment showed that compared to two ecotypes, Mashhad ecotype compared to Tehran has more tolerance to water shortage.