| 题名 | 水分胁迫对玉米幼苗形态建成、生理代谢及根系吸水的影响 |
| 学位类别 | 博士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 陕西 |
| 导师 | 邓西平 |
| 学位专业 | 生态学 |
| 中文摘要 | 水分亏缺是限制干旱与半干旱地区作物生产的一个主要因素，同时作物的芽苗期又是对水分亏缺较为敏感的时期，水分不足会影响到作物的出苗、生长以及幼苗的成活率，进而给作物产量的形成带来较大损失。因此，在旱地农业生产中，作物幼苗的根系吸水能力及其对水分胁迫的生理响应和适应机制显得尤为重要。基于此，本研究以玉米幼苗为试验材料，采用PEG 6000模拟根际干旱的方法，主要研究了干旱胁迫下幼苗的形态建成、各个不同器官对干旱条件的敏感性差异、根系吸水能力与其形态、生理特征、光合气体交换等生理参数之间的关系，以及干旱胁迫对根系在整株和单根水平上水力学特性的影响，并且对根压力探针技术测定根系水力学参数进行了探讨。主要的研究结果如下：1. 通过对玉米幼苗从萌发到成苗这一过程中胚芽鞘、中胚轴、根系各个部位形态指标的研究，结果表明在幼苗的出土过程中，中胚轴对水分条件的变化最不敏感，胚芽鞘的生长最容易受到水分亏缺的影响，而根系在水分胁迫条件下仍然能够保持生长良好，这说明作物为了保证幼苗的正常出土，首先要保证幼苗具有出土动力，以及水分和养分的吸收器官的形成，即首先保证中胚轴和根系的生长，才能保证幼苗的正常出土与成苗。2. 通过对玉米幼苗不同部位的组织含水量、渗透调节物质积累、活性氧的产生和膜质过氧化程度以及活性氧清除系统等几个方面的研究，结果表明干旱条件下，各个部位的组织含水量均有所下降，其中叶片的含水量下降最为严重；脯氨酸、可溶性糖、可溶性蛋白等渗透调节物质的含量也有了很大幅度的提高；干旱胁迫致使活性氧在玉米各个部位都有了不同程度地累积，MDA含量和相对膜透性也明显增加，其中在叶片中的含量最高；为了减轻或者避免活性氧积累造成的伤害，各个器官的保护酶活性和活性氧清除剂的含量也均有很大程度的提高。综上所述，玉米幼苗的叶片最容易受到干旱胁迫的影响，根系次之，然后是中胚轴，最后是茎。3. 玉米幼苗的茎充满空气，不宜与根压力探针相连来测定整株根系的水力学特性，而中胚轴与之连接则能够成功地对其进行测定。但是该测定要求中胚轴的长度至少2cm以上。所以该方法比较适用于中胚轴可伸长的作物如水稻、高粱、谷子等，由于小麦的中胚轴不伸长，所以不宜采用该方法进行测定。另外该方法需要在玉米3-4叶期以前进行，因为随着苗龄的增大，中胚轴上将萌发不定根，容易对测定结果产生较大影响。4. 采用压力室、根压力探针、高压液流测定仪对两种水分条件下玉米幼苗根系导水率的测定，均发现水分胁迫显著降低了玉米幼苗根系的导水率。根压力探针技术适用于3-4叶期以前的水培或盆栽幼苗，而压力室技术对苗龄的要求相对比较宽松，如果测定盆栽植株则需要特殊的培养容器或特殊的压力室，而高压液流测定仪更适用于测定各个阶段的大田作物。5. 通过对水分胁迫条件下玉米幼苗根系导水性及根系形态、生理参数，以及光合作用和气体交换参数的研究表明，正常水分条件下，随着苗龄增加，玉米幼苗的吸水能力逐渐增强，而水分胁迫降低了其增长速率，同时随着胁迫时间的延长，导水性开始下降。这是由根系的形态变化、根系生理活动以及地上部气体交换能力的变化共同作用引起的。通过对相关参数进行回归分析发现，根系吸水能力的下降主要是由根系活力、根系活跃吸收面积、根鲜重的变化引起的。另一方面，可能由于所测玉米比较幼小，处于生长迅速的时期，以及所使用测定技术不是非离体根系的稳态流法，所以根系导水性与地上部叶片蒸腾速率和气孔导度之间的相关性不强。6. 采用根压力探针技术对玉米幼苗整株根系及单根的水分及溶质运移参数进行了研究，水分胁迫对整株根系和单根的根压、导水率、溶质透过能力均存在抑制作用，并且随着胁迫时间的延长，该抑制作用也增大。因此，从整体上看，水分胁迫对整株根系影响大于对单根的影响。 |
| 英文摘要 | Water is the most important resourse limiting crop production in arid and semi-arid area. Moreover, seedlings establishment period is one of the critical phase in the life cycle of seed plant. The seedlings are prone to be damaged since they are too young to endure these adverse conditions. The establishment and survival of seedling would be impaired; furtherly crop productivity was lowered greatly. In the practical theory of rain-fed agriculture, there are two significant points to ensure crop productivity: one is the physiological adaptive ability of crops; the other is water uptake ability of root. Therefore, corn seedlings were grown hydroponically, and drought stress simulated by PEG 6000 was imposed on these corn seedlings. The present study was mainly performed from those two aspects: response of corn to water stress during as its seedling stage; hydraulic properties of corn root under different water condition as well as techniques for hydraulic properties measuremens. The major results are as following: 1. During the period of corn seedlings establishment, different parts of young seedlings respond differently to water stress. Coleoptile development of seedlings were greatly impaired by water stress, while the adverse effects of water stress on mesocotyl is the least, compared to the other two parts (Coleoptile and root). It was notice-worthy that root developed better than control under mild water stress or under short duration of sever stress. It indicated that mesocotyl and root growth were ensure priorly, because mesocotyl elongation is the driving force of seedling establishment, and root is the prime organ obtaining water and nutrients. Nevertheless, seedling establishment required longer time underwater stress.2. Water content, osmolates accumulation, reactive oxygen species, membrane lipid peroxidation and oxygen radicals scavenging systems of four parts of corn seedlings were studied. The results showed water content of four parts declined, leaves water content decreased mostly under water stress; the content of proline, solubale sugar and soluble protein in all four parts increased remarkably; ROS accumulated in the four parts with different extent; the content of MDA and relative membrane permeability increased significantly, the increment of them were the greatest in leaves; protective enzyme activity and ROS scavenger content increased to prevent seedlings from the damage of excess ROS. Therefore, corn seedling leaves were the most susceptible to water stress, followed with root system, mesocotyl and stem.3. Corn young seedling stem is not appropriate to connect with RPP because air could not be completely removed from measurement system. Connecting RPP with mesocotyl of corn seedling can solve this problem. However, at least 2 cm mesocotyl is necessary to mount on RPP. Nevertheless, this method could not be used on corn seedlings that are older than three-four leaf stage, because the adventitious root will emerge on mesocotyl and the nodes between shoot and mesocotyl while plants grow. It indicated that hydraulic conductivity of root system of corn seedling could be measured by connecting mesocotyl with RPP. To some extent, it realizes the measurements of corn root system properties in situ, and provides technical promotion for further studying on gramineous plant relations at different levels. 4. Hydraulic conductivity for root systems of hydroponically corn seedlings with normal and drought conditions were measured using root pressure probe, high pressure flow meter, pressure chamber. The result showed drought simulated by PEG 6000 reduced hydraulic conductivity significantly. Moreover, three methods gave comparable results for those root systems of seedlings. Root pressure probe work best with such young seedlings before 2-3 leaf-stage grown hydroponically or grown in pots; the requirements of seedling age during measurements with pressure chamber was not strict, while HPFM can be used for plants at all age in the field 5. The hydraulic conductance, the morphological and physiological parameters of corn root system as well as photosynthetic parameters were investigated. The results showed under normal water condition root water uptake ability increased gradually as seedling aging. However, water stress hampered the increasing of it, and the water uptake ability decreased with duration of water stress. This was resulted from the change of root morphology, physiological metabolism and photosynthesis capacity. With correlation analysis, it is found the decrease of root water uptake ability was mainly resulted from root vigor, root active surface area and fresh weight. On the other hand, the correlation between hydraulic conductance and transpiration rate as well as stomatal conductance were not significant, it might be due to seedling was too young, and growing fast, as well as the measuring root system was exised from shoot.6. Hydraulic properties and solute transport parameters were studied at the level of individual root and whole root system by root pressure probe. It demonstrated water stress decreased root pressure, root hydrdaulic conductivity and solute permeability of whole root system, and the decrease aggravated with duration of wate stress. In general, water stress inhibited parameters mentioned above in whole root system more than individual root. |
| 公开日期 | 2011-07-01 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.iswc.ac.cn/handle/361005/4069]  |
| 专题 | 水土保持研究所_水保所知识产出(1956-2013) |
| 推荐引用方式 GB/T 7714 | . 水分胁迫对玉米幼苗形态建成、生理代谢及根系吸水的影响[D]. 陕西. 中国科学院研究生院. 2009. |
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