羊草干物质积累及叶片气体交换对土壤水分的响应

采用盆栽方法模拟羊草干物质积累和叶片气体交换参数对 5个水分梯度的响应表明 :轻度、中度干旱与对照相比 ,羊草叶片的相对含水量 (RWC )有所升高 ;严重和极严重干旱使RWC显著降低。干旱降低植株生物量 ,后期的降低幅度远远大于前期 ,反映出羊草叶片水分状况对适度的土壤干旱具有良好的适应性 ,而过度干旱对羊草的生长造成威胁。鞘的分配随时间呈下降趋势 ,而根茎的趋势与鞘相反 ,表明鞘的暂储物质有可能向根茎转移。干旱促进早期根的分配和根冠比增加 ,后期降低 ,表明羊草在受到持续干旱后 ,通过增加根部的比重来提高抗旱性的能力逐渐降低。干旱降低了光合速率 ,增加了胞间CO2 浓度 ,但对水分利用率 (WUE )的影响随日进程而波动 ,在上午 10时干旱促进了WUE升高 ,其他时间无显著影响 ,表明光合参数对干旱的响应受日进程影响。

Response of the Dry Matter Accumulation and Leaf Gas Exchange of Leymus chinensis to Soil Moisture Content

An experiment is carried out to study the dry matter accumulation and leaf gas exchange of Leymus chinensis and their response to 5 levels of soil moisture content. Leaf relative water content (RWC) increases sensitively under the light and moderate soil drought, but reduces significantly under the severe drought. Soil drought reduces the biomass of plants, especially at the later growth stage. It is suggested that the leaf water status may be regulated adaptively by soil drought, and the growth of plants is limited by extreme soil drought. The sheath allocation decreases gradually with the plant growth, but conversely for rhizome, suggesting the translocation from the matter in stored sheath to rhizome. Soil drought increases the root allocation and the ratio of roots shooting in the earlier stage, which reveals that the plants' capability of drought resistance by increasing roots decreases gradually after the soil suffers droughts for a long time. Soil drought reduces the leaf photosynthetic rate, increases the intercellular CO 2 content, but raises the water use efficiency only at about 10 a.m., these reveal that the responses of photosynthetic parameters to soil drought may change with time.