Changes in morphophysiological traits and alkaloids yield of rosea periwinkle (Catharanthus roseus L. (G. Don)) in response to plant growth regulators under drought stress conditions

This research was aimed to investigate the foliar application of Plant Growth Regulators (PGRs) on growth parameters, yield, some morphophysiological traits, and alkaloids of rosea periwinkle (Catharanthus roseus L. (G. Don) under drought stress conditions. The field study was conducted based on split-plot factorial in the randomized complete block design (RCBD) with three replications at the research farms of Shahid Chamran University in Ahwaz city in 2016-17. The experimental treatments included drought stress as the main factor at three levels of 40% (control), 60% and 80% of maximum allowable depletion (MAD) and foliar application of jasmonic acid (JA) at two levels (0 and 10 µM) and salicylic acid (SA) at three levels (0, 0.1, 1, and 10 mM) as subplots. Based on the results of the mean comparison of main effects, drought stress (80% MAD) reduced 36.6% of fresh weight and 25.4% of the dry weight of the plant compared to the control. The treatment 10 mM SA resulted in 13.4, 125.5, and 59.6% increases in plant height, leaf area and flower dry weight, respectively, compared to the control. The foliar application of JA increased flower dry weight and plant fresh weight by 16.3 and 8.6%, respectively. The results showed that the foliar application of SA in concentrations of 1 and 10 mM caused the highest content of vincristine and vinblastine, respectively. The interaction of both PGRs and drought stress showed the highest alkaloids content. The highest vinblastine and vincristine under severe drought stress were obtained in foliar application of 1 mM SA+10µM JA and 10 mM SA+10µM JA, respectively.