Influencia de diferentes regímenes de riego y tiempo de siembra en la calidad y cantidad del cáliz, el contenido de aceite de las semillas y la eficiencia del uso del agua de la roselle (Hibiscus sabdariffa L.)

This study was carried out to examine the physiological traits, quality of calyx extract and seed oil content of roselle (Hibiscus sabdariffa L.) as affected by irrigation regimes and planting dates. The growth period from seed sowing to calyx harvesting was shortened as planting time was delayed. Stem diameter and plant height were decreased by drought stress or late planting, but calyx yield, total phenolic content, total anthocyanin content, vitamin C, and calyx water use efficiency increased under mild drought condition. In addition, antioxidant activity and calyx water use efficiency were significantly increased by late planting. It was suggested that an increase in calyx harvest index in delay in planting would be due to better photosynthesis activity and higher assimilate use efficiency because of the increase in sink capacity. Seed oil content decreased considerably due to drought stress and delay in planting date. These findings suggest that mild drought stress improves the quality and quantity of calyx and water use efficiency.Este estudio se llevó a cabo para examinar los rasgos fisiológicos, la calidad del extracto de cáliz y el contenido de aceite de semillas de roselle (Hibiscus sabdariffa L.) afectado por regímenes de riego y fecha de siembra. El período de crecimiento desde la siembra de la semilla hasta la cosecha del cáliz se acortó debido a que se retrasó el tiempo de siembra. El diámetro del tallo y la altura de la planta disminuyeron por el estrés por sequía o la siembra tardía, pero el rendimiento del cáliz, el contenido fenólico total, el contenido total de antocianinas, la vitamina C y la eficiencia del uso del agua del cáliz aumentaron en condiciones de sequía leve. Además, la actividad antioxidante y la eficiencia del uso del agua del cáliz aumentaron significativamente en la siembra tardía. Se sugirió que el aumento del índice de cosecha del cáliz en la demora en la siembra se debería a una mejor actividad de fotosíntesis y una mayor eficiencia en el uso de asimilación debido al aumento de la capacidad de hundimiento. El contenido de aceite de las semillas disminuyó considerablemente debido al estrés por sequía y al retraso en la fecha de siembra. Estos hallazgos sugieren que el estrés por sequía leve mejora la calidad y cantidad del cáliz y la eficiencia del uso del agua

Investigation of the role of exogenous use of sucrose as an osmoprotectant in increasing Azolla filiculoides resistance to air high temperature and salt stress

Influence of 2.75 to 11 moles sucrose as an exogenous osmoprotectant on salt stressed (7.8-9.1 and 18.2 ms/cm) and temperature stressed (42.36°C) Azolla (A. filiculoides Lam.) was studied. Results showed that enriching salt stressed (9.1 ms/cm) Azolla by 5.5 moles sucrose significantly increased survival percent (S%) and freshness percent (F%), in comparison with control treatment in which no sucrose was used. Enriching Azolla media by 2.75, 5.5 and 8.25 moles sucrose in optimum growth condition (24.18C and 0.65 mS/cm), had no significant effects on growth doubling time (D.T), S% and F% in comparison with control. Enriching Azolla media by 11 moles sucrose in optimum growth condition decreased significantly the S% and F%, in comparison with control plots. Enriching Azolla media by 5.5 moles sucrose, in all salinity levels (0.65, 7.8, 9.1 and 18.25 ms/cm), and air temperatures (24.18 and 42.36C), non-increased S% and F% but not significantly and decreased D.T.A positive correlation was observed between high air temperature and medium salinity in Azolla growth