【作者】 郭颖；

【导师】 韩蕊莲；

【作者基本信息】 西北农林科技大学 ， 植物学， 2010， 硕士

【摘要】 以黄土高原4个乡土禾草:长芒草(Stipa bungeana)白羊草(Bothriochloa ischaemum),无芒隐子草(Cleistogenes songorica),冰草(Agropyron cristatum)作为实验材料,应用盆栽试验,在中国科学院水土保持研究中心的遮雨棚模拟黄土高原干旱环境,人工控制土壤水分并设置3个梯度:适宜水分(75%θf)、中度干旱(55%θf)、重度干旱(40%θf);对这4个乡土禾本科牧草在不同土壤水分条件下的耗水规律、生长特性、叶绿体色素成分和含量、水分生理特性、保护酶活性和渗透调节物质、水分利用效率及干物质积累分配规律等进行研究,探讨了4个乡土禾本科牧草在不同土壤水分条件下这些指标在时间和空间上的变化规律,从而揭示这4个乡土禾本科牧草在耗水规律、水分利用策略、抗旱生理机制以及抗旱性的差异,旨在为黄土高原草地建设提供参考价值,也为乡土禾草的应用提供理论依据。主要结论如下:1. 4个乡土禾本科牧草的耗水特性存在差异。4个乡土禾草的月耗水量及总耗水量均表现为:适宜水分>中度干旱>重度干旱。4个乡土禾草月耗水主要集中在6、7月份,且在7月份达到峰值。随干旱胁迫程度加剧,各草种耗水量明显减少;不同草种单株耗水量差异明显,表现为:白羊草>冰草>无芒隐子草>长芒草,最高日、旬、月耗水量差异明显,中度和重度水分亏缺下的最高耗水日比适宜水分下的提前10 d左右。1 d中的最大耗水高峰随着土壤含水量的降低有提前的趋势。2. 4个草种株高生长和单叶叶面积明显受土壤水分含量影响,均表现为:适宜水分>中度干旱>重度干旱,土壤干旱下长芒草和无芒隐子草受抑制程度显著大于冰草和白羊草;干旱胁迫均抑制了4个草种地上部的生长,但同时却提高了根冠比。土壤水分含量对4个草种的水分利用效率均有较大影响,长芒草和无芒隐子草的水分利用效率随干旱加剧而降低,两者属于低耗水、低WUE草种,冰草和白羊草在中度干旱下WUE最高,相比白羊草,冰草属于低耗水、高WUE草种;白羊草属于高耗水、高WUE草种。3.随干旱胁迫程度的加剧和干旱时间的延长,长芒草和无芒隐子草的叶片组织含水量和叶片相对含水量明显降低,冰草和白羊草则一直能维持较高含水量,且下降幅度小,稳定性好,并且冰草和白羊草利用自身高度保水力的特点来适应干旱环境。另外,随着干旱的不断加剧会减慢抑制叶绿体色素的合成,但抗旱性较强的冰草和白羊草叶绿素含量下降速度比抗旱性较弱的长芒草和无芒隐子草慢,即白羊草和冰草在一定干旱胁迫下能保持原本的叶绿素含量甚至含量增多,所以能维持正常的光合作用。4. 4个乡土禾草的保护酶活性和渗透调节物质在整个干旱胁迫期间对不同土壤水分条件的反应不同。结果表明:这4个草种在开始遭受干旱胁迫时,均造成MDA含量增加,O2-·的积累,同时,这4个草种SOD、POD、CAT、APX的活性上下波动协调作用,脯氨酸、可溶性糖、可溶性蛋白和K+含量在干旱下连续积累,这些渗透调节物质和保护酶共同作用,使O2-·和MDA含量在胁迫中后期呈下降趋势。在胁迫前期和中期,主要是以增强保护酶活性来有效地清除活性氧,抑制膜脂过氧化,而在胁迫后期,随着酶活降低,则靠增加渗透调节能力来适应干旱。冰草和白羊草在干旱胁迫下脯氨酸、可溶性糖、可溶性蛋白的积累比长芒草和无芒隐子草更多;无芒隐子草在干旱胁迫下渗透调节物质无机离子的积累量明显比其它三个草种多,说明渗透调节物质之间互相有补充的作用,不同草种主要的渗透调节物质对渗透调节作用的贡献率不同。本文采用主成分分析方法对这4个乡土禾草的抗旱性进行综合评价,结果表明4个禾草的抗旱性为:冰草>白羊草>长芒草>无芒隐子草。更多还原

【Abstract】 The growth development, strategy of water using and drought-resistance mechanism of four native gramineous grass(Stipa bungeana, Bothriochloa ischaemum, Cleistogenes songorica and Agropyron cristatum) in Loess plateau were studied by pot culture experiments simulating different soil water status in Yangling of China. The different levels of soil-water-treatments were set by artificially controlling soil moisture. This paper mainly studied the time and space changes of water metabolism and growth, photosynthesis characteristic and photosynthesis pigment, water physiological characters, protective enzymes activities, osmotic adjustment substances, WUE ,and the community biomass of four species, expecting to discover the differences of the drought-resistance ability and the strategy of water-using between them. The results provided scientific basis of vegetation restoration and community succession in Loess plateau. The main results are as follows:1. Different soil water content had obviously affected on water consumption characteristics of four species. The trends of water consumption of four species in a month and the total water consumption were adequate water(75%θf)>medium stress(55%θf)>severe stress(40%θf). The results showed that water consumption of those species decreased with the increase of soil drought stress, and water consumption of those grasses was different: Bothriochloa ischaemum>Agropyron cristatum> Cleistogenes songorica>Stipa bungeana. The highest water consumption in one day, ten-day and one month were different. The highest water consumption day of medium and severe drought stress occurred about 10 days earlier than the adequate soil water content. The time of day when the greatest water consumption occurred arrived early with the decrease of soil water contents.2. The growth of plant height and single leaf area of the four native grasses were the fastest under adequate soil water contents, and were the lowest under severe drought .Under drought condition, the growth of four grasses was all inhibited, especially for S. bungeana and C. songorica. The growth of four species had been restrained and WUE was affected strongly under drought stress. Water use efficiency of S. bungeana and C. songorica decreased with the decrease of soil water content, they had lower water consumption and low WUE characteristics. A. cristatum and B. ischaemum had the highest WUE under medium drought treatments, respectively. A. cristatum had low water consumption and high WUE characteristic, B. ischaemum had high water consumption and high WUE characteristic.3. The leaf water content of different species decreased with the increase of soil water stress. The RWC of A. cristatum and B. ischaemum were higher than that of S. bungeana and C. songorica obviously under three different soil water conditions in the different growth stage, and maintained stable range, had better water preserving capacity. Besides, the content of photosynthesis pigment of four species decreased at early stress stage under three soil water conditions, which shows that drought-stress affected the synthesis of photosynthesis pigment .But the content of photosynthesis pigment of A. cristatum and B. ischaemum were higher than that of S. bungeana and C. songorica obviously under drought treatments to keep the normal metabolism.4. The effects of protective enzymes activities and osmotic adjustment substances were different on four species under different water contents. The content of O2-·and the content of MDA increased under drought stress. With the extending of water stress, the activity of four species enzymes, such as SOD, POD, CAT, APX in the leaves of the four species were up-down fluctuating, and coordinated interactively. In the meanwhile, the content of osmoregulation substance, such as proline, soluble sugar, soluble protein, and K+, accumulated continuously under drought stress, which combined action with protective enzymes above and made the content of O2-·and the content of MDA down in the middle-later period. At the early and middle water stress stages, they may boost up the protective enzymes activities to protect the endosmosis from damaging. As the protective enzymes activities weaker at the following stage, they may adopt the strategy of improving osmotic adjustment substances content to adapt drought. The content of proline, soluble sugar and soluble protein of A. cristatum and B. ischaemum were more than those of S. bungeana and C. songorica under drought treatments. But the content of K+, Ca2+ and Na+ of C. songorica were more than the others. Main components analysis was conducted to reveal the ability of drought-resistance of four species. The result is A. cristatum >B. ischaemum>S. bungeana > C. songorica.更多还原