EFFECT OF WATER STRESS ON VEGETATIVE GROWTH AND NITROGEN METABOLISM OF POMEGRANATE SEEDLING

Abstract

Water deficit is one of the serious environmental stresses that affect pomegranate growth, fruit production and quality. Pomegranate is one of the most valuable fruit tree crops in China. The objective of this study was to quantify the effects of water-deficit stress on leaf and shoot growth and leaf concentrations of arginine, praline, polyamines, and related metabolites in pomegranate compared with non-water-deficit treated pomegranate seedlings. Replicate pots, each containing one young seedling in 2 L of soil, were subjected to water deficit by withholding water or were maintained under well-watered (control) conditions. Water stress reduced both total and shoot dry matter (DW), but increased root DW and the value of root/shoot, compared to the control. Plant height and stem diameter were reduced by 26.53 and 34.93% respectively. Water stress decreased protein concentration in leaves of pomegranate, under well watered condition, leaves protein content of pomegranate was 16.72 mg/g fresh weight. However, when soil water was withheld to 20% water content treatment, leaves protein content was 7.19 mg/g fresh weight, decreased by 52.69%. Water stress increased leaf concentration of NH3-NH4+, arginine and proline. Under well watered condition, NH3-NH4+, Arginine and Proline concentrations of young, fully expanded leaves of pomegranate were the lowest, and these values were the highest at 20% water content treatment. Compared with control plants, concentrations of NH3-NH4+ in pomegranate leaves at 20% water content treatment increased 149.93%; free arginine concentration increased 79.96%; and concentration of proline increased 171.62%.