干旱胁迫及复水对耐旱枸杞水力学特性的影响

耐旱枸杞是西北干旱地区重要的经济作物,为进一步明确枸杞水分运输特性,提高农业生产潜力,在甘肃省古浪县农业示范基地(37.09°N,102.79°E)以2年生‘宁杞1号’、‘宁杞5号’和‘蒙杞1号’3个枸杞品种苗木为试验材料,设计3个处理N:正常水分;M:中度干旱;S:重度干旱],研究干旱胁迫对光合速率、气孔导度、冠层和根系导水率的影响,以及干旱胁迫后复水对枝条导水率的影响。结果表明:随着干旱程度增加,枸杞冠层、枝条和根系导水率均下降,‘宁杞5号’在干旱胁迫后植株导水率的减小和根系导水阻力在整个植株中所占比例的增大最显著;通过拟合木质部脆弱性曲线发现,‘宁杞1号’导水率损失50%时木质部水势显著高于‘宁杞5号’和‘蒙杞1号’。枸杞叶片净光合速率和气孔导度与植株叶片导水速率具有显著相关性。干旱胁迫复水后植物生长主要取决于根系恢复吸水的能力,干旱胁迫复水4 d后苗木导水率呈现不同程度的恢复,‘蒙杞1号’导水率恢复速度最快,并出现显著补偿效应,恢复速度最慢的为‘宁杞5号’。综合分析表明,枸杞耐旱特性与导水能力有关,根系导水对干旱胁迫的敏感性可以反映植株持续抗旱能力,干旱胁迫复水后根系导水率恢复能力和补偿效应对植株在逆境条件下土壤水分利用具有显著影响,调控根系导水率对于提高土壤水分利用率具有重要意义。

Hydraulic characteristics of Lycium barbarum L. seedlings under drought stress and re-watering conditions

Lycium barbarum L. is the main commercial crop across the arid lands in northwestern China, which is drought resistant with various functions, such as soil improvement, soil fertility enhancement. To determine water transport characteristics and increase the potential for agricultural productivity of L. barbarum, we conducted a pot experiment at the agricultural demonstration site in Gulang, Gansu Province (37.09oN, 102.79oE). The experiment consisted of 3 treatments — normal water application (N), moderate drought (M) and severe drought (S). The hydraulics characteristics of the canopy and root, photosynthetic rate (Pn) and stomatal conductance (Gs) were monitored in 2-year-old seedlings of 'Ningqi 1', 'Ningqi 5' and 'Mengqi 1' varieties of L. barbarum during drought stress. The effect of re-watering after drought stress on the hydraulics characteristics of the shoot system was determined inthe study. The results showed that hydraulic conductance of canopy, shoot and root gradually declined with increasing drought stress. Also hydraulic conductance of the plant decreased with increasing degree of drought stress and the ratio of root to plant (Rroot/Rplant) hydraulic conductance resistance increased the most in 'Ningqi 5'. It was also noted that the canopy equation of xylem embolism vulnerability curve in L. barbarum seedlings and xylem water potential loss of hydraulic conductance was 50% in 'Ningqi 1', sig-nificant higher than those in 'Ningqi 5' and 'Mengqi 1'. Also there was a statistically significant correlation (P < 0.05) among spe-cific hydraulic conductance of leaf (Kl,leaf) and stomatal conductance (Gs) as well as photosynthetic rate (Pn) of leaf of L. barbarum. The growth of plants after drought stress was largely determined by the ability of root system to absorb water following re-watering after 4 days of drought stress. The recovery of hydraulic conductance was fastest with the most obvious compensation effect of water transportation for 'Mengqi 1' and the slowest hydraulic conductance recovery for 'Ningqi 5'. The results suggested that drought-tolerate characteristics was associated with hydraulic conductance in L. barbarum. Hydraulic sensitivity of root to drought stress reflected a continuous capacity of plant to resist drought. The ability of the root system to recover from drought stress and compensation effect was critical for plant soil water utilization under adverse conditions. It was important to regulate the hydraulic conductance of roots for improvement of soil water use efficiency.