【作者】 曹让；

【导师】 梁宗锁； 张继澍；

【作者基本信息】 西北农林科技大学 ， 植物学， 2004， 硕士

【摘要】 干旱下植物根系感知土壤水分状况后，会产生一种信号传递到地上部分，控制气孔行为以最有效的利用水分。目前大多数人认为，ABA是一种主要根源信号，但是否是唯一的信号还存在有争议。干旱下木质部汁液中会发生许多显著的变化，例如pH，氨基酸，多糖等的变化。这些因子是单独或与ABA一起起根源信号的作用还不清楚。本研究以玉米（陕单9号）为材料，通过溶液培养试验，采用分根交替渗透胁迫的方法，研究了水分胁迫下玉米幼苗叶片，木质部汁液和根系中游离氨基酸以及木质部汁液中蛋白的变化与渗透胁迫强度与时间的关系，探讨了这些变化是否具有根源信号的功能。研究结果表明：1. 在-0.2MPa和–0.5MPa的分根交替渗透胁迫处理中各叶水势高于全部根系渗透胁迫的处理，另外-0.2MPa的分根交替渗透胁迫处理叶水势与未胁迫对照接近，而-0.5MPa的分根交替渗透胁迫处理与-0.2MPa的全渗透胁迫处理接近，说明分根交替渗透胁迫能保证胁迫下叶水分状况的维持。在不同的渗透胁迫处理下玉米苗叶片中的可溶性糖和游离氨基酸含量的变化趋势相似，都是随着胁迫强度的增加和胁迫时间的延长含量增高。其中在-0.5Mpa的分根交替渗透胁迫中可溶性糖和游离氨基酸的变化最大。 2. 在玉米苗叶片、木质部汁液和根系中天冬氨酸、丝氨酸、苏氨酸、谷氨酸、丙氨酸的含量之和占总游离氨基酸含量的50%以上，且随着胁迫强度和时间的延长而增加。另外，在叶片中甘氨酸和组氨酸的含量也较高，在根系中缬氨酸和组氨酸的含量较高，在木质部汁液中缬氨酸，异亮氨酸，亮氨酸和赖氨酸的含量较高。在木质部汁液中苏氨酸和丝氨酸随胁迫强度的增加变化最为显著，二者从完全分离的峰混合为一个峰。在叶片和根系中游离脯氨酸的变化范围分别为26.65-143.09mg/100g和6.14-23.57mg/100g，是随胁迫强度变化最大的氨基酸。3. 玉米苗叶片中在各种胁迫强度下均未检测出精氨酸的存在，在木质部汁液中未检测出胱氨酸,且蛋氨酸含量一直在0.2mg/100g左右变动。4. 随着渗透胁迫强度的增加和胁迫时间的延长,木质部汁液中的可溶性蛋白质组分主要在14.4~31KD范围内变化。 5. 在-0.5MPa分根交替渗透胁迫处理下,当一半根系受到胁迫时，其游离氨基酸的含量上升，第二天将这部分根系交替到正常营养液中时，其游离氨基酸的含量明显下降，第三天再进行渗透胁迫时游离氨基酸的含量比前一次胁迫下又有所上升。总之在分根交替渗透胁迫下玉米根系中的游离氨基酸含量是波浪式上升的。在-0.5MPa固定分根渗透胁迫下，处在正常营养液中的根系的游离氨基酸含量随着胁迫时间的延长而上升，但低于分根交替根系中的含量；处在胁迫下的根系中游离氨基酸含量也随着胁迫时间的延长而上升，但含量高于分根交替渗透胁迫处理，而低于全渗透胁迫处理。更多还原

【Abstract】 Some research have shown that when plant roots sense the change of soil water condition, it would produce a few signals and transfer to leaves with transpiration stream to control the stoma behavior, so that plants can use water optimumly, At present, many people take ABA as an important root signal, but whether it is an only signal is still a controversial issue, because of other substances, such as pH, amino acid, sugar et al, are also thought as signals act together with ABA. Using maize (zea mays.L) as material, we have researched the relationship between osmotic stress, stress time and amino acids, protein in leaves, xylem sap and roots of maize seedlings using alternative split-root osmotic stress under solution culture, discussed the role they played in whole plant, the results showed:Maize leaves water potential are higher under –0.2MPa and –0.5MPa alternative split-root osmotic stress than those under whole root osmotic stress. Among them, those under –0.2MPa alternative split root stress are closer with those under contrast, and the same results are gotten under –0.5MPa alternative split-root stress compared with –0.2MPa whole root osmotic stress, which showed that alternative split-root osmotic stress can increase leaf water potential. The change of soluble sugar and free amino acids are similar under different osmotic stress, that is, the content would increase with the stress degree stronger and the stress time longer, especially under –0.5MPa alternative split-root osmotic stress.The amount of Asp, Ser, Thr, Glu and Ala are over 50% of total free amino acids, and which would increase with the stress degree stronger and the stress time longer. Furthermore, the amount of Gly and His is higher in leaves, also the Val and His in roots, the Val ，Ile， Leu,and Lys in xylem sap. The Thr and Ser change greatly with the increasing of stress degree. For example, their two independent peaks emerged into one peak in chromatography. The amount of Pro change significantly compared with other amino acids, which present in leaves from 26.65 to 143.09 mg∕100g, and in roots from 6.14 to 23.57 mg∕100g.Among all the treatments, some amino acids are undetected, such as Asp in leaves Cys in roots, and the amount of Met is always remained in 0.2mg∕100g or so in roots.With the stress degree stronger and the stress time longer, the protein in xylem sap changed among 14.4~31KD for all alternative split-root osmotic stress.For roots under –0.5MPa alternative split-root osmotic stress, the amount of amino acids were increased in the stress part, but which were decreased significantly when putting them into common solution; when the condition change to stress again the amount increase again, taken together, the amount of free amino acids increase in a wave way in roots of maize seedlings Under alternative split-root osmotic stress. The amount of free amino acids increase <WP=7>with the increased treatment time in roots grow in usual condition under –0.5MPa fixed osmotic stress, but lower than that under alternative split-root treatment; the amount in roots grow in stress show the same tendency, but higher than that under alternative split-root treatment and lower than while root stress.更多还原