Physiological and growth responses of Lycium barbarum seedlings to water and salt stresses

Rational exploitation and utilization of brackish water resources is the basis of sustainable agricultural development in the oasis regions of arid inland basin. As a drought-and-salt-tolerant economic crop, irrigation management at seedling stage is particularly important for the fruit yield in Lycium barbarum adulthood. The effects of three irrigation levels (the lower limits of irrigation were 80 % (full irrigation), 70 %, and 60 % of field capacity) and two salinity levels in irrigation water (1.7 (fresh water) and 5.0 dS/m) on physiology and growth of Lycium barbarum seedlings were studied through pot experiments. The results showed that water deficit treatment promoted aboveground plant growth and water use efficiency, but decreased transpiration rate of Lycium barbarum seedlings. Compared with full irrigation, the averaged leaf chlorophyll content (SPAD), base stem diameter, branch diameter, and water use efficiency of Lycium barbarum seedlings under deficit irrigation treatments were increased by 4.6 % - 6.6 %, 15.1 % - 55.5 %, 12.8 % - 41.0 %, and 22.3 % - 23.9 %, respectively, while the transpiration rate was decreased by 6.5 % - 16.1 %. Soil water content under brackish water irrigation was generally slightly higher than that under freshwater irrigation, but its soil salinity was about 5.0 times higher than that under freshwater irrigation. Compared with freshwater irrigation, brackish water irrigation decreased root biomass by 6.7% - 9.0 % and transpiration rate by 2.5% - 10.5 %, and increased water use efficiency by 1.9 % - 24.8 %, and meanwhile it also promoted the growth of base stem (11.4 % - 32.4 %), branch (6.4 % - 18.9 %) and leaf aera (2.2 % - 6.8 %). The lower limit of irrigation and the salinity in irrigation water imposed significant interactive effects on photosynthesis, stem and branch growth, and crop water consumption of Lycium barbarum seedlings. The analysis results of structural equation model showed that the lower limit of irrigation mainly affected water use efficiency of Lycium barbarum seedlings, while the salinity in irrigation water mainly did its root biomass. The lower limit of irrigation with 70 % field capacity may be a preferred scheme of brackish water irrigation for the planting of Lycium barbarum seedlings in arid oasis regions.