低磷胁迫对山核桃幼苗根系形态和生理特征的影响

Root morphology and physiological characteristics in Carya cathayensis seedlings with low phosphorus stress

通过水培实验比较了山核桃Carya cathayensis幼苗在正常供磷(0.10mmol·L-1)和低磷胁迫(0.02mmol·L-1)条件下的根系形态、磷营养特点、叶片光合作用以及叶片和根系分泌酸性磷酸酶活性的差异。结果表明,低磷处理显著降低山核桃植株干质量、磷质量分数和磷积累量(P<0.05);与正常供磷相比,低磷处理条件下山核桃根长、根表面积和根体积显著降低(P<0.05);低磷处理显著降低山核桃叶片光合速率和气孔导度(P<0.05),但对叶片胞间二氧化碳摩尔分数无显著影响,这表明低磷胁迫对山核桃叶片光合速率的抑制作用主要是由于非气孔因素引起的。低磷胁迫使山核桃叶片酸性磷酸酶活性和根系分泌酸性磷酸酶活性显著增加(P<0.05),分别为正常供磷处理下的135%和159%,这表明磷缺乏诱导酸性磷酸酶活性的增加可能是山核桃适应低磷胁迫的机制之一。

Phosphorus （P） deficiency is one of the limiting factors to plant growth. However, scarce information is available about the effect of P deficiency on the growth of Carya cathayensis. To study root morphology, leaf photosynthesis characteristics, leaf acid phosphatase, and root secreted acid phosphatase of Carya cathayensis seedlings, a hydroponic culture experiment with treatments of sufficient P （0.1 mmol·L-1） or deficient P （0.02 mmol ·L-1） was conducted. Results showed that compared to sufficient P, the low P treatment significantly decreased（P〈0.05） plant dry weight, plant P concentration, plant P accumulation, root length, root surface area, root volume leaf photosynthetic rate, and stomatal conductance; however, there were no significant differences for intercellular C02 concentration. Additionally, the low P treatment significantly increased （P〈0.05） leaf acid phosphatase （by 135%） and root secreted acid phosphatase （by 159% ）. Thus, the low P treatments with decreases in leaf photosynthetic rate and stomatal conductance, but no differences for intercellular CO2 concentration, showed that leaf photosynthetic rate was not due to stomatal limitation. Also, for C. cathayensis an increase in acid phosphatase activity induced by a P deficiency could be an adaptive mechanism to low P stress. [Ch, 4 fig. 1 tab. 28 ref.]