Drought stress, mercuric chloride, and β-mercaptoethanol effects on hydraulic characteristics of three cultivars of wolfberry (Lycium chinense)

In order to further understand the effects of drought stress on hydraulic characteristics and the relationship between hydraulic conductivity and aquaporins or water channels of root systems of three wolfberry cultivars (Lycium chinense Mill.), hydraulic conductivity of 2-year-old pot-grown seedlings was measured under drought stress, rewatering, and treatment with exogenous mercuric chloride and β-mercaptoethanol. Under moderate and severe drought stress levels, the most significant decrease of hydraulic conductivity was 37.3% and 24.0%, respectively, in the ‘Ningqi 5’ cultivar compared with the non-stressed control. After rewatering, the rate of recovery in specific conductivity was most rapid in the ‘Mengqi 1’ cultivar, at 0.058 and 0.072 kg MPa−1 m−2 s−1 h−1 under moderate and severe drought stress levels, respectively. The ‘Mengqi 1’ cultivar had the highest recovery degree of hydraulic conductivity under two concentrations of β-ME (500 or 1000 μmol L− 1), reaching 82.4% and 88.5%, respectively, of the initial conductivity. The adaptive capacity of hydraulic conductivity in the ‘Ningqi 5’ cultivar was weaker than in the ‘Ningqi 1’ and ‘Mengqi 1’ cultivars under drought stress. The recovery capacity of hydraulic conductivity in ‘Mengqi 1’ cultivar was stronger than the ‘Ningqi 1’ and ‘Ningqi 5’ cultivars after rewatering. Aquaporins of the ‘Ningqi 1’ cultivar root systems had the highest binding affinity with mercuric chloride, which was the most likely cause in the decrease in hydraulic conductivity, whereas aquaporins of ‘Mengqi 1’ root systems had the weakest binding affinity. The inhibitory effect of mercuric chloride was readily eliminated by β-mercaptoethanol in the ‘Mengqi 1’ cultivar. The hydraulic characteristics of this cultivar were more sensitive to drought, mercuric chloride and β-mercaptoethanol than the other cultivars.