【作者】 陈银萍；

【导师】 王勋陵； 安黎哲； 张满效； 陈拓；

【作者基本信息】 兰州大学 ， 生态学， 2006， 博士

【摘要】 我国幅员辽阔,低温伤害是限制植物自然分布和栽培区带的主要因素,也是全国性的自然灾害之一。每年因植物受低温伤害而造成的巨大经济损失,已引起我国政府部门和科技工作者的高度重视。因此,研究低温胁迫对植物的伤害作用及其机理,探索植物抗冷冻机制及其预防措施,不仅对于引种栽培具有理论上的指导意义,而且对于发展培育较多品种的抗冻植物,增加寒冷地区的生物学产量和经济学产量具有广泛的应用价值。圆柏属植物在我国西北广泛分布,有关其抗冷冻适应性机制的研究目前尚未报道。本研究以祁连圆柏(Sabina przewalskii)和圆柏(Sabina chinensis)为材料,通过测定叶片内源一氧化氮(NO)和抗氧化系统,水分、渗透调节物和无机元素,稳定碳同位素组成,观察显微和超微结构,分析它们与植物冷适应、越冬间的关系,以探讨常绿木本植物的抗冷冻性适应机制。研究表明: (1) 随秋季气温下降,过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸氧化酶(APX)活性和谷胱甘肽(GSH)、脯氨酸(Pro)、类胡萝卜素(Car)含量增加并在冬季达最大值,NO释放率、NOS和NR活性以及丙二醛(MDA)含量也显著增加并在秋季和初春出现两峰值;两树种叶中的抗氧化酶活性和抗氧化剂含量都与温度和MDA含量明显负相关,表明抗氧化系统在清除氧自由基、抑制膜脂过氧化、提高抗冷冻性方面具有重要作用;而且NO的产生总是发生在抗氧化酶活性和抗氧化剂含量增加之前,表明NO作为信号分子激活了抗氧化系统以诱导植物的抗冷冻性。在抗冷冻过程中祁连圆柏叶的NO释放率、NOS和NR活性、抗氧化酶活性以及抗氧化剂含量都高于圆柏,表明祁连圆柏具有较强的抗冷冻适应性策略。 (2) 随秋季气温下降,叶片组织相对含水量(RWC)、自由水含量(FWC)下降,束缚水含量(BWC)、脯氨酸(Pro)、游离氨基酸(FAA)、可溶性蛋白质(SP)、可溶性糖(SS)含量增加,翌年春季气温回升,相对含水量和自由水含量增加,束缚水含量下降,有机渗透调节物再次增加。有机渗透调节物在秋末冬初及初春的增加正好与圆柏属植物抗冻锻炼及脱冻恢复生长的时间相吻合,因而是植物抗冻及脱冻适应的重要生理响应,在降低细胞冰点、防止细胞结冰引起的膜机械伤害、抑制膜脂过氧化、保护膜稳定性方面具有重要作用。祁连圆柏的相对含水量和自由水含量均低于圆柏,3种有机渗透调节物含量均高于圆柏,表明祁连圆柏在抗冷冻性诱导更多还原

【Abstract】 The freezing injury limited the distribution of plants and the chilling stress is one of the natural disasters prevailed in China. The huge economic losses resulted from freezing injury were concerned seriously by Chinese Government and scientific researchers. Therefore, studies on adaptive mechanisms of plants to chilling stress are very important;it will not only be a guide to introduction and cultivation of plants but also help to breed anti-freezing plants. However, there was no report about the physiological mechanism of evergreen woody plants of Sabina in northwest China during winter stress. The leaves of Sabina przewalskii and Sabina chinensis were used to explore the cold resistant mechanism of evergreen woody plants of Sabina by examining seasonal changes of the endogenous nitric oxide, anti-oxidative system, water content, osmoregulation substance, element, microstructure, ultra structure, stable carbon isotope. The results showed as follows:(1) The activities of CAT, POD and APX, contents of GSH, Pro and Car increased with temperature decrease, and the highest value occurred in the winter. The MDA content, NO release rate, NOS and NR activities increased markedly and reached two peaks in autumn and early spring, respectively. Meanwhile, the activities of POD, CAT, APX and the contents of GSH, Car and Pro were negatively correlated with mean temperature and MDA content in both species, it indicated that the anti-oxidative systems played an important role in potentiating freezing-resistance of plant and limiting the production of free radicals to protect membrane integrity. Furthermore, NO generation is always found before increasing of anti-oxidative enzyme activity and antioxidant content, it indicated that NO as an early signal molecule is able to induce the freezing tolerance by activating the anti-oxidative system involved in both anti-oxidative enzyme and antioxidant. S. przewalskii showed a prevailing strategy in signal function of NO and the higher anti-oxidative enzyme activity and antioxidant content than S. chinensis in order to develop the tolerance to freezing.(2) In the leaves of the two species, the relative water content (RWC) and free water content (FWC) decreased during hardening in autumn, but bound water content (BWC)and organic osmoticas accumulated and remained relatively higher level over winter. In spring, RWC and FWC increased, BWC decreased, and organic osmotica accumulated again. These seasonal patterns were consistent with winter hardening and dehardening. Organic osmotica may supply nutrients to regrowth in spring and contribute to the stabilization of the cell membrane by preventing lipid peroxidation and by binding the tissue water. The results also suggested that a better capacity for osmoregulation in S. przewalskii might account for its greater capacity for freezing tolerance than S. chinensis.(3) The concentrations of N, K and Cl in the leaves of two species in summer and autumn were higher than that in winter and spring, and this indicated that two species enriched abundant nutrient matters in summer and autumn, which were identical with accumulating higher biomass in these two seasons. The concentrations of P, Ca, Mg, Na, Si and S in the leaves of two species in winter and spring were higher than that in summer and autumn, and this indicated that two species could accumulate abundant inorganic osmotica to adapt itself to low temperature by increasing osmotic pressure of the cell. The results also suggested that a better capacity for accumulating inorganic osmotica in S. przewalskii might account for its greater capacity for freezing tolerance than S. chinensis.(4) It was shown that the foliar surface cells were covered with thick cuticular membrane, and the well-developed arenchyma appeared inside of their mesophyll in S. przewalskii and S. chinensis. It was observed in the two species that starch grains in chloroplasts accumulated in growing season and disappeared or diminished as soluble sugar content increased in cold season, but there was a larger increase in soluble sugar content in S. przewalskii than S. chinensis. Chloroplasts of S. chinensis were injured in winter, with some chloroplasts become abnormal, plastoglobuli increased and some lipid drops were observed, but no obvious injury in the chloroplasts of S. przewalskii had been observed. Mitochondria of both species remained stable and intact in dormancy season. It can be concluded that cold tolerance of two species related to the well-developed arenchyma, accumulation of starch grains in developing seasons, and increase of soluble sugar in dormancy season. Moreover, more stable chloroplasts and more marked increase of soluble sugar content in S. przewalskii under low-temperature stress might account for its greater capacity for freezing tolerance than S. chinensis.(5) The 5BC values in the leaves of the two species declined with monthly average temperature decreasing and maintained a relatively lower value in the whole winter. It indicated that the two species consumed more self substances in order to adapt to low temperature. As a result, the 813C values decreased. The 813C values of S. przewalskii were markedly higher than those of S. chinensis, it suggested that S. chinensis must consume more self substances than S. przewalskii under low-temperature stress. S. przewalskii showed a more prevailing strategy than & chinensis in order to develop the tolerance to freezing. Furthermore, very significant linear relationships were observed between 613C value and monthly average temperature, between 513C value and Pro content, and between 513C value and RWC in the leaves of S. przewalskii and S. chinensis. These results suggested that the 813C values of two species of Sabina can be used as another index to evaluate freezing tolerance.In conclusion, the well-developed arenchyma, accumulation of starch grains in growing seasons, increase of soluble sugar in dormancy season, signal function of NO to activate the anti-oxidative system, accumulation of organic and inorganic osmotica, stability of chloroplasts, and decrease of 513C value under low-temperature stress were important adaptive mechanisms of plants of Sabina in order to develop the tolerance to freezing.更多还原