水分胁迫下紫花苜蓿根系特征与ABA含量的变化

研究通过温室盆栽试验探讨了干旱胁迫对‘三得利’、‘敖汉’和‘中苜1 号’3 个紫花苜蓿品种根系ABA浓度和根系特征的影响。按照田间持水量的100%（对照）、85%（轻度干旱）、70%（中度干旱）和55%（重度干旱）设置4 个梯度的水分胁迫处理，分别对3 个紫花苜蓿品种进行处理，并对根系ABA含量和根系性状进行测量。结果显示：水分胁迫可以显著影响不同生长时期的紫花苜蓿根系ABA的含量。随着处理时间的延长，不同水分胁迫处理的紫花苜蓿根系ABA含量均呈先升高后下降再升高的趋势。在移栽后的第75 天，根系ABA含量达到首个峰值，然后开始下降，到第105 天的时候将至最低，然后开始回升直至处理结束。移栽105 天以后，4 个水分胁迫处理（W1、W2、W3 和W4）紫花苜蓿根系ABA含量分别为44、56.6、64.6、94.4 ng/g FW。同时，不同紫花苜蓿品种根系ABA含量存在差异。移栽105 天以后，‘敖汉’、‘三得利’和‘中苜1 号’根系ABA含量均达到最低，分别为83.2 ng/g FW、61.7 ng/g.FW 和49.9 ng/g FW；之后，根系ABA含量开始回升。与对照相比，重度水分胁迫使根系长度降低了20.92%，使侧根数降低了20.71%，使根鲜重降低了43.79%，使根干重降低了37.96%。重度水分胁迫下植株根冠比是对照的1.9倍，这说明水分胁迫对地上部茎叶的影响要大于地下部的根系。水分胁迫降低了紫花苜蓿根长、侧根数、根鲜重和根干重，增加了紫花苜蓿根冠比，促使根系ABA含量升高。不同紫花苜蓿品种根系ABA含量存在差异。

Effect of Water Stress on ABA of Roots and Root Characteristics of Alfalfa

The effects of drought stress on Abscisic acid (ABA) in roots and root characteristics of three alfalfa varieties‘Suntory’,‘Ohan’ and‘Zhongmu No.1’ were studied by greenhouse pot experiment. The experiment was conducted with three alfalfa varieties, and four gradients of water stress were set up with four filed water capacities, 100% (control, W1), 85% (mild drought, W2), 70% (moderate drought, W3) and 55% (severe drought, W4). And then ABA of the root and the characteristics of root were measured. The results showed that ABA was significantly affected by deficit irrigation treatments during different times of plant ages. With the extension of treatment time, the content of ABA in alfalfa root under different water stress treatments showed a trend of first increasing then decreasing, and increased at last. 75 days after transplanting, the root ABA content reached the peak, and then began to decline. The root ABA content was approaching the minimum on the 105th day, and then began to pick up until the end of the treatment. 105 days after transplanting, the content of ABA of four water stress treatments (W1, W2, W3 and W4) was 44, 56.6, 64.6 and 94.4 ng/g FW, respectively. Moreover the results showed that the content of ABA in different alfalfa roots had differences. 105 days after transplanting, the content of ABA n‘Ohan’,‘ Suntory’and‘Zhongmu No.1’ reached the minimum as 83.2, 61.7 and 49.9 ng/g FW, respectively. And then, the content of ABA began to increase. Compared with the control, the highest water stress (W4) reduced root length by 20.92%, lateral roots by 20.71%, root fresh biomass by 43.79% and root dry biomass by 37.96%. The root to shoot ratio was 1.9 times higher in water stressed plants, showing that water stress in alfalfa plant affected more on shoots than on roots. Water stress reduced the alfalfa root length, lateral root number, root fresh biomass and root dry biomass, increased the alfalfa root to shoot ratio, and prompted the content of ABA. The ABA content of root of different alfalfa varieties had distinguished differences.