土壤水分梯度对白三叶(Trifolium repens)光合作用和根系分布的影响

Effects of soil water gradient on photosynthesis and root spatial distribution in two Trifolium repens cultivars

通过对两个品种白三叶Trifolium repenscv.Haifa（海发）和Trifolium repenscv.Rivendel（瑞文德）盆栽试验,模拟3种不同的土壤水分状况（无水分胁迫：保持植株良好的水分供应;轻度胁迫：表层0-20 cm土壤处于干旱状态;重度胁迫：表层0-20 cm土壤处于极干旱状态,20-40 cm土壤处于干旱状态）对白三叶光合作用和根系生长的影响。结果表明,当植株未遭受水分胁迫时,两个品种白三叶的光合作用和根系生长状况没有明显差异;当表层0-20 cm处于干旱状态时,‘海发’在处理后期的净光合速率和水分利用效率升高,根系生长量增大,表现出促进作用,‘瑞文德’受到的影响不显著;当表层0-20 cm处于极干旱、20-40cm处于干旱状态时,‘海发’在处理前期受到轻微影响,随后恢复正常状态,‘瑞文德’则受到较严重的影响。随着干旱程度的加深和时间的延长,白三叶的根冠比逐渐增大。与‘瑞文德’相比,在相同时期相同胁迫程度下,‘海发’的根冠比没有显著差异,但深根数量大大超过‘瑞文德’,因而,‘海发’的耐旱能力强于‘瑞文德’。

The plant drought tolerance is one of the important parameters for selecting sustainable landscape plants. In this paper Trifolium repens Cuhivars, ＇ Haifa＇ and ＇ Rivendel＇, were studied for their photosynthesis and root spatial distribution under different drought stresses. These two varities were grown separately in the 15cm diam, 60cm deep pots, and irrigated for 81 d. Pots were then either irrigated or subjected to water deficit （ CK ： no water stress ; LS ： the up 20 cm soil was under the state of drought ; HS ： the up 20 cm soil was under the state of extreme drought, and the 20 - 40 cm soil was under the state of drought）. The results showed that there were no differences in plant photosynthesis or root growth between the two cuhivars under adequate water supply. Net photosynthetic rates and water use efficiency increased, and the root growth Was enhanced for ＇ Haifa＇ with moderate water stress in the 0 - 20 cm soil layer, but there was no significant change for ＇ Rivendel＇. Under extreme drought condition in 0 - 20 cm soil, and drought condition in 20 - 40 cm soil, the cultivar ＇Haifa＇ was affected only slightly at the first stage of the experiment and later recovered to a normal state, while ＇Rivendel＇ was much more adversely effected. Degree and time of the moisture stress increased the rot/shoot ratios gradually for plants of ＇ Rivendel＇. Compared to ＇ Rivendel＇, the root/shoot ratio for ＇ Haifa＇ did not increase significantly given the same experiment conditions as ＇ Haifa＇ , but there were more deeper roots for ＇ Haifa＇ than for ＇ Rivendel＇. Therefore, it is believed that ＇ Haifa＇ was more drought resistant than ＇ Rivendel＇.