Effects of NaCl on Growth and Photosynthesis of Semi-dwarf Blueberry Bushes

  Objective  Salt tolerance of blueberry plants were studied for possible cultivation in saline-alkali lands.

  Method  A pot experiment was conducted using varied salt additions [0(CK), 30, 60, 90, 120, 150, 180, and 210 mmol·L^-1)] NaCl in a medium to artificially simulate the environmental stress. Two-year-old seedlings of semi-dwarf Vaccinium Northland blueberry were treated under the stress for 50d. Effects on the physiological and biochemical properties, as well as the photosynthesis, net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO₂ concentration (Ci), and stomatal conductance (Gs), were determined.

  Result  (1) A salt concentration at 30, 60 or 90 mmol·L^-1 promoted the seedling growth, but the enhancing effect disappeared when it reached 120 mmol·L^-1, where the result became similar to CK. Further increase to 150 or 180 mmol·L^-1 inhibited the seedling growth. At 210 mmol·L^-1, a threshold that caused plant death was observed. (2) When the salt concentration was less or equal to 90 mmol·L^-1, the blueberry seedlings grew better than CK with increased plant height, crown width, dry and fresh weights of shoots, and soluble sugar content in leaves. The biochemical indices, such as Pro, superoxide dismutase (SOD) activity, relative permeability of cell membrane, and malondialdehyde (MDA) content, were elevated as well. (3) The daily variations on Pn, Tr and Gs of the treated plants were on an upward trend, but Ci downward. The responses of Pn, Tr and Ci to light exposure showed an upward trend, while that of Gs downward. These effects were most significant under 60 mmol·L^-1 NaCl.

  Conclusion  The semi-dwarf blueberry bushes exhibited a significant salt tolerance within 0-180 mmol·L^-1. Northland blueberry was conceivably a variety that could be cultivated on soil that has a salt content below 90 mmol·L^-1.