植物导水系统对土壤质地与辐射强度的形态性适应研究

Adaptative Morphological Responses of Plant Water-conducting System to Soil Texture and Radiation

以棉花(Gossyp ium herbaceum L.)为实验材料,在全生长期为盆栽植株设置3个土壤质地梯度、3个蒸发力梯度.在播种后50 d和90 d,测定总根长与总叶面积;同时,在90 d时,使用热脉冲探头和HR-33T露点微伏计测定植株茎流和叶水势,并由此确定导水度,以期了解植物导水系统对土壤质地与大气蒸发力的长期适应.结果表明:在蒸发需求相同的条件下,生长在沙土中、单位根导水度低的植株,形成的吸收根要多于生长在粘土中、单位根导水度高的植株;单位叶片导水度在3种不同的土壤中没有显著差别.在土壤质地相同条件下,高蒸发力下生长的植株比低蒸发力下生长的植株产生更多的吸收根、形成更高的单位叶片导水度.最终证实:当土壤质地或大气蒸发力发生变化时,植物个体可以通过导水系统的形态性适应来调节根-叶比例,以达到协调其自身水分供需平衡.

Cotton was pot planted under three soil textures and at three evaporativities. Its root lengths ,total leaf area were measured on the fiftieth and ninetieth days after planting and thermal pulse probe and HR-33-TR Dew Point Micro-voltmeter were employed to measure the stem flow and leaf water potential of cotton plants on the ninetieth day after planting; the measured stem flow and leaf water potentials were used determine the water-conductance in order to understand the long-term adaptation of plant water conducting system to soil texture and evaporation. The results showed that under the same evaporative conditions,the plants that grew in sandy soil and had a low root specific water conductance formed more absorbing roots than those which grew in clay soil and had a high root specific water conductance and the water conductance did not differ among the three soil texture. Under the same soil textures,the plants at a high evaporativity formed more absorbing roots and a much higher leaf-specific water conductance than those at a low evaporativity. It was finally proved that where soil texture and air evaporation varied,the plants will regulate their root-leaf ratios through the morphological adaptations of their water conducting system tokeep their water balanced.