【作者】 王宇通；

【导师】 王堃； 邵新庆；

【作者基本信息】 中国农业大学 ， 草业科学， 2014， 博士

【摘要】 植物衰老是受内外因子直接或者间接影响的器官或组织逐步走向衰退和死亡的变化过程。全叶马兰是根蘖型多年生菊科草本植物,具有较强的营养繁殖能力和种子繁殖能力。本文以不同生长年限的全叶马兰为研究材料,从植株衰老的形态特征、种子质量、光合作用与蒸腾作用特征、生理生化代谢特征等方面进行了系统性的研究,同时采用15N示踪技术研究了全叶马兰衰老过程中氮素分布以及运移规律,旨在掌握全叶马兰衰老特征特性以及在衰老过程中氮代谢变化的规律,丰富多年生草本植物衰老理论,为草原生态系统的建设和维持提供必要的理论指导。研究结果表明：(1)随着生长年限的增加,全叶马兰形态特征和种子质量发生明显变化。株高、根长、分支数逐渐升高,生长年限为1年的全叶马兰植株各项指标均较低。植株生物量的分配规律为茎>叶>根>种子。伴随生长年限的增加,地上生物量与地下生物量均有增加趋势。与之相反,全叶马兰种子繁殖能力随生长年限的增加而有所减弱。全叶马兰生长过程中根毛数量动态变化呈现先升高后降低的“钟形曲线”。根毛数量在7月份达到最大值,而后根毛逐渐脱落。与1、2龄级相比,7月份过后生长年限为三年的全叶马兰植株根毛数量锐减。就种子质量而言,生长年限为3年的全叶马兰所结种子品质较差。3龄植株所结种子的芽率、发芽势、发芽指数显著低于较年轻植株所结种子的各项指标,同时3龄株种子霉变率较高,种子所含的过氧化氢酶和过氧化物酶活性也较低,种子活力较差。(2)全叶马兰光合作用、蒸腾作用日变化动态有明显的季节性特征,并在龄级之间呈现出一定的差异性。夏季和秋季净光合速率日变化曲线都为双峰曲线,但夏季净光合速率多数时间都保持在较高水平。不同生长年限的植株夏季净光合速率日变化规律并无明显不同。秋季与夏季不同,生长年限为3年的全叶马兰各时间点的净光合速率显著低于1、2龄级全叶马兰。全叶马兰蒸腾速率日变化动态也显示出明显的季节性特征。夏季蒸腾速率日变化呈双峰曲线,而秋季则呈单峰曲线。夏季不同生长年限植株的蒸腾速率无明显差异,秋季3龄植株蒸腾速率较低,与1、2龄级差异显著。夏季与秋季的蒸腾速率均存在饱和现象。蒸腾速率随有效光辐射的增强而增强,达到饱和有效光辐射后蒸腾速率不再增加。(3)生长过程中植物体内调节物质的含量发生着变化,这些变化反映了衰老的进程。研究发现各器官中脯氨酸含量、丙二醛含量、活性氧自由基含量随着生长周期的推移有所增加,而SOD活性则下降。各类内含物质的含量或活性及其在生长过程中含量或活性的变化幅度在各器官中略有差异。激素是调节衰老以及氮代谢的重要物质,全叶马兰衰老过程中细胞分裂素、生长素、赤霉素在各器官中的含量基本呈现先上升后下降的趋势,但不同器官中激素含量变化幅度不尽相同。不同龄级植株中各类激素含量变化情况略有差异。(4)全叶马兰衰老过程中,氮含量、氮代谢相关酶的活性先上升后下降。不同器官中蛋白质含量、游离氨基酸含量先上升,到6月份达到峰值后下降。全叶马兰生长过程中,植株总氮量占干物质比重先上升后下降,各器官中硝酸还原酶活性、谷氨酰胺合成酶活性与之变化趋势相似。酶活性在不同龄级植株上有一定差异。(5)营养生长阶段,全叶马兰植株氮主要在茎叶中,根中氮素含量较低。新生营养器官的氮源为较老的茎和叶片。生殖生长阶段,幼嫩营养器官以及生殖器官为氮库,氮源为根和较老的主茎以及主茎上的叶片。不同生长年限的全叶马兰植株氮素移动效率差异明显。更多还原

【Abstract】 Plant senescence can be described as a process of decline and death which may be affected directly or indirectly by internal and external factors. Kalimeris integrifolia is a root sucker form perennial herb of compositae, meanwhile, it has relatively strong capability of vegetative and seed reproduction. In this study we used Kalimeris integrifolia as the model plant and material, to study the characteristics of morphology of plant, seed quality, characteristics of photosynthesis and transpiration, characteristics of physiology and biochemistry metabolism during plant senescence. Meanwhile, we adopted15N tracing method to study nitrogen distribution and mobilization during senescence of Kalimeris integrifolia, So that we can make clear the regular pattern of nitrogen metabolism during the senescence of Kalimeris integrifolia, enrich the theory of perennial plant senescence. That can help to prove some necessary theoretical direction in the activities of building and maintaining the grassland ecosystem. The results are as follows:(1) Morphology and seed quality of Kalimeris integrifolia varied obviously as the increasing of growing year. Plant height, length of root, number of branches saw an increasing trend.1year old(ly) plants got the lowest plant height, length of root and the number of branches which were significantly lower than2(2y) and3years old(3y) Kalimeris integrifolia. The characteristic of biomass participation in Kalimeris integrifolia is stems> leaves> roots> seeds. As the increase of growing year, above ground biomass and underground biomass got up gradually. On the contrast, the capability of seed reproduction of Kalimeris integrifolia decrease,3years old plants had the worse seed reproduction capability, it had an worse seeds output and seeds quality.Root is an important plant absorbing organs that help plant absorb nutrients, root hairs is the main function part of root. The number of root hairs reflects the capability of nutrients absorption. In the growing season ofKalimeris integrifolia, number of root hairs varied. This number of root hair varied following an "bell-shaped curve", in July it got the peak and after July root hairs dropped quickly. Compared with1y and2y plants, root hairs of3y plant dropped more quickly. When it comes to seed quality, seeds that form3y plant had the worse seed quality. The1000-seed weight, germination rate, Germination energy, Germination index in seeds from3y plant were lower, while, seeds in this group were more easier Infected by mold. Seeds from1y and2y plant had higher catalase,Peroxidase activity and seed vigor.(2)Net photosynthetic rate diurnal variation of Kalimeris integrifolia showed seasonal characteristics. It was saw a "bimodal curve" in both summer and autumn. The difference was that in most of the time net photosynthetic rate in summer keeps a higher level. There was no significant difference in net photosynthetic rate in summer among plants with different ages, but in autumn the differences were significantly. Photosynthetic rate In every time interval in3y plant was lower. As similar with net photosynthetic rate diurnal variation, diurnal variation of transpiration rate in Kalimeris integrifolia also saw some seasonal characteristics obviously. In summer, transpiration rate diurnal variation performed a "bimodal curve", but in autumn it acted a "unimodal curve". There were no significant differences among the plants with different ages in summer. When it comes to autumn, the conditions were that3y plant showed a lower transpiration rate in the whole day comparedwith1y and2y plants. In both summer and autumn, transpiration rate of Kalimeris integrifolia had the phenomenon of "saturation", that means the transpiration rate increased as the increasing of effective radiation, after it reached the peak the transpiration rate would not increase along with effective radiation increasing.(3) The senescence of Kalimeris integrifolia happened as its vegetative growth stopped and started the reproductive growth. As the plants growth and development the growth regulating substances content was always changing, these changes reflected the process of senescence. According to the determination results, proline content, malondialdehyde content, active oxygen free radicals content risealong with plants growth and development. While SOD activity decreased. Substances content/activity and their amplitude of variation during plant life cycle had some tiny differences in different kind of organs of Kalimeris integrifolia. Hormones are important regulated materials in the process of senescence and nitrogen metabolism. During the senescence of Kalimeris integrifolia, cytokinins, gibberellins and auxin content increased until they got the peak, after that the content dropped in different organs. Among these three hormones, gibberellins and auxin content had tinier amplitude of variation. Content of abscisic acid and ethylene rose obvious gradually as life cycle backwards in time. Hormones content are a little differently in different organs.1y and2y plants had higher cytokinins, gibberellins and auxin content than those in3y plants, and lower abscisic acid and ethylene content.(4)During senescence of Kalimeris integrifolia, protein content and free amino acid content in different organs increased, in June they got the top, after that the content dropped. Along with growing, whole plant nitrogen quantity/whole plant biomass rate also got a "bell-shaped curve", that was similar with the variation of nitrate reductase and glutamine synthetase activity during the same period. Enzymes activities were seen some differences in the plants with different ages.(5)In vegetative growth stage, nitrogen stored mainly in stems and leaves of Kalimeris integrifolia. The nitrogen sources of new born vegetative organs were older main stem and leaves on it, roots were not the nitrogen source in this period. Nitrogen sinks were the seed and tender new born vegetative organs, while sources were roots and older main stem as well as leaves on main stem. Significant differences were seen in plants with different ages.更多还原