【作者】 种培芳；

【导师】 李毅；

【作者基本信息】 甘肃农业大学 ， 水土保持与荒漠化防治， 2010， 博士

【摘要】 红砂、白刺和沙拐枣抗旱、耐盐、耐高温,是干旱、半干旱地区防风、固沙和水土保持的优良植物。它们广泛分布于我国干旱荒漠地区,特别广布于西北的半干旱地区,其抗逆性强,生态可塑性大,具有很强的抗旱和集沙能力。因此研究这三种荒漠植物的抗旱性对其植被保护和恢复以及为荒漠植物抗逆性研究具有重要的意义。本文以分布于不同地区的红砂、白刺和沙拐枣为材料,通过对自然干旱条件下三种荒漠植物的光合特性、荧光特性、水分生理、相关代谢物质的变化、酶活性变化以及叶绿素的变化进行了研究,以期进一步阐明这三种荒漠植物的抗旱机制,并对它们进行抗旱性综合评价。主要研究结果如下:1.三种荒漠植物的光合、蒸腾速率日变化曲线特征可以分为两类:(1)双峰型,包括红砂;(2)单峰型,包括白刺和沙拐枣。而按光合、蒸腾强弱划分可以分为3类:(1)低光合、低蒸腾型,包括红砂;(2)高光合,高蒸腾型,包括白刺;(3)低光合、高蒸腾型,有沙拐枣。在环境因子中,光合有效辐射是影响三种植物光合和蒸腾速率的最重要因子;中午高光强造成白刺和沙拐枣的光抑制现象,但并未对红砂产生光抑制效应。三种植物的光合最适宜温度范围分别为红砂25~30℃,白刺28~32℃,沙拐枣35~37℃。水分条件是导致地区间植物光合和蒸腾速率产生差异主要因素,而且空气相对湿度主要对植物的蒸腾速率起作用。在内在因素中,红砂光合午休以及沙拐枣10:00以前光合强弱的主要原因是气孔因素,并且干旱加剧会提高这两种植物的气孔调节能力。白刺气孔调节能力受诸多环境因子以及植物因素影响,但白刺气孔调节对光合的作用大于对蒸腾的作用。结果表明,在水分条件降低时,红砂通过气孔调节和渗透调节来提高水分利用效率;白刺的水分利用效率则随一天环境条件的改变而变化;沙拐枣由于光合碳同化途径的不同,以及植物本身蒸腾特性的差异,使其水分利用效率始终高于其它两种植物。2.强光尽管使红砂光合作用的Fv/Fm和ΦPSⅡ下降,却并没有发生光抑制现象;水分是引起红砂光化学效率下降主要因素,而光化学效率下降是红砂光合午休的非气孔因素之一。强光引起了白刺和沙拐枣的光抑制现象发生,而且水分条件的降低则加剧了这种现象,但沙拐枣光抑制出现有滞后现象,说明其光抑制较轻。在强光、高温及干旱环境中红砂主要依赖于叶黄素循环的热能耗散机制使其光合机构得以保护,而不是光抑制因素;而白刺和沙拐枣则既依赖于叶黄素循环的热能耗散又依赖于光抑制。3.三种荒漠植物的水分生理变化表明:从WP的角度来说,红砂的耐旱能力最强,沙拐枣最弱;而按照RWC和WSD判断则以沙拐枣的抗旱性最强,红砂最低。4.研究发现,在干旱荒漠区Pro和SS在水分匮乏的情况下短时积累是有益,是植物干旱忍耐的一种方式,但在不同植物中的作用不同。以Pro和SS的高低来判断三种植物的抗旱性顺序为红砂﹥白刺﹥沙拐枣。三种荒漠植物在水分减少时均引发膜脂过氧化作用和超氧自由基产生速率加快,造成了对细胞膜系统的破坏。以MDA含量和O2-.产生速率来判断这三种植物的抗旱性顺序应该为沙拐枣﹥红砂﹥白刺。在水分亏缺时,沙拐枣通过提高SOD和CAT酶活性来抵御干旱伤害的作用强于其它两种植物,而POD对三种植物在极端干旱条件下的保护能力是有限。按SOD和CAT的作用来判断三种植物的抗旱性顺序为红砂﹥白刺﹥沙拐枣。本实验条件下的土壤含水量对红砂和白刺造成了干旱胁迫,从而引起它们体内Chl的减少;而在相同条件下对沙拐枣构成的胁迫较小,其体内的Chl含量升高,说明沙拐枣对水分条件的改变反应迟缓。5.结果显示,不同地区红砂的抗旱性强弱顺序为:WWM﹥JQJ﹥ZYL﹥LZJ;不同地区白刺的抗旱性强弱顺序为:JQJ﹥WWM﹥ZYL﹥LZJ;不同地区沙拐枣的抗旱性强弱顺序为:JQJ﹥WWM﹥ZYL。可以看出,水分条件越差得地区植物的抗旱性越强,这是植物通过自身生理调节对外部环境条件产生适应的结果。6.研究结果表明,本实验所测的18项指标在红砂、白刺和沙拐枣的抗旱性中相互制约,相互依赖,综合调节着它们的内在抗旱机制。但通过降低蒸腾速率来提高水分利用效率、依赖于叶黄素循环的热能耗散机制以及以Pro为主的渗透调节这3大机制在红砂的抗旱机制中占有重要的地位;而依赖于叶黄素循环的热能耗散机制和光抑制的光保护机制在白刺的抗旱机制中占有主导地位。沙拐枣的抗旱机制比红砂和白刺的复杂,其以较强的保持水、贮水能力和很高的水分利用率适应土壤与大气干旱的双重胁迫,同时在其它两种植物中不占有重要地位的叶绿素和SOD、CAT酶活性机制在沙拐枣的抗旱机制中表现也较为突出。更多还原

【Abstract】 Reaumuria soongorica, Nitraria tangutorum and Calligomum mongolicum are the best plants to prevent wind and sand , to conservate soil and water at the arid and semi-arid areas because they are drought-resistant,salt-resistant and high temperature-resistant. They are wide-ranging distributed over desert especially over semi-arid area of NorthWest, and they have the drought-resistant ablities. So it is very important to study the drought-resistance of these plants. This paper presented the studies on the change of photosynthetic characteristic, chlorophyll fluorescence characteristic, water physiology, metabolic products, activities of enzyme and chlorophyll in Reaumuria soongorica, Nitraria tangutorum and Calligomum mongolicum from four area (LZJ, WWM, ZYL and JQJ) under natural environment. This studies were analyzed and discussed to elucidate further the mechanisms of drought-resistance in the three plants,and comprehensive evaluated their drought-resistance.The main results were summarized as follows:1. Diurnal changes of net photosynthetic rate and transpiration rate in leaves of Reaumuria soongorica, Nitraria tangutorum and Calligomum mongolicum could be classified tow types:(1) bimodal curve, including Reaumuria soongorica,(2)single curve, including Nitraria tangutorum and Calligomum mongolicum; Their phtosynthetic typy could be classified tow typies: (1)low net photosynthetic rate(Pn) and transpiration rate(Tr) , including Reaumuria soongorica,(2)high Pn and Tr, including Nitraria tangutorum,(3) low Pn and high Tr, including Calligomum mongolicum. Among the environmental factors, photosynthetically active radiation (PAR) had a leading effect on both Pn and Tr ,the high light intensity of noon caused photoinhibition on Nitraria tangutorum and Calligomum mongolicum,but did not produce on Reaumuria soongorica. The scope of the most suitable photosynthetic temperature of the three plants are 25~30℃(Reaumuria soongorica),28~32℃(Nitraria tangutorum)and 35~37℃(Calligomum mongolicum) respectively. Water condition was the main factor that caused the different Pn and Tr of different area, and relative humidity (RH)mainly effected on Tr. Among internal factors, stomatal conductance (Gs) was the major determinant of midday depression in Pn of Reaumuria soongorica and Pn before 10:00 of Calligomum mongolicum, and the water stress would increase the Gs ability of the tow plants. The Gs adjustment ability of Nitraria tangutorum was effected by many factors, but the ability effected on Pn more than on Tr. The results showed that under the water stress condition, Reaumuria soongorica increased water use efficiency(WUE) through adjusting its Gs and osmoregulation matters; WUE of Nitraria tangutorum changed with the enviromrntal condition,while WUE of Calligomum mongolicum was all over higher than other plants because its different photosynthetic way and transpiraion property.2. A decline in maximal photochemical efficiency of PSII (Fv/Fm) and actual photochemistry efficiency(ΦPSⅡ) but not photoinhibition of Reaumuria soongorica was caused by high light intensity. The decline of photochemical efficiency of PSII which was one of non-stomatal factors on midday depression in Pn of Reaumuria soongorica was caused by drought stress.High light intensity produced photoinhibition of Nitraria tangutorum and Calligomum mongolicum,and the decline of soil water aggravated this phenomenon.The photoinhibition of Calligomum mongolicum was not serious because it lagged behind that of Nitraria tangutorum. The major photoprotective mechanism which helped Reaumuria soongorica to adap the adverse circumstances was the xanthophyll cycle_dependent thermal energy dissipation but not the photoinhibition under extreme soil drought coupling with high temperature, strong solar radiation and low air humidity,while Nitraria tangutorum and Calligomum mongolicum were dependent on tow photoprotective mechanisms.3. The changes of water physiology in three desert plants from different area showed that the drought resistant capability of three desert plants decreased in order of Reaumuria soongorica, Nitraria tangutorum and Calligomum mongolicum from water potential(WP), but in order of Calligomum mongolicum, Nitraria tangutorum and Reaumuria soongorica from relative water content(RWC) and water saturation deficit (WSD).4.The results showed that it was useful to accumulate proline (Pro) and soluble sugar (SS) in short time under the water deficient in desert, it was the way that plants restrain drought stess,but the condition was different in different plants. The drought resistant capability of three desert shrub plants decreased in order of Reaumuria soongorica, Nitraria tangutorum and Calligomum mongolicum from Pro and SS. The content of malondialdehyde ( MDA) and O2-. production rate of three plants from different area were increased under the water deficient ,and it destroyed the cytomembrane. The drought resistant capability of three desert plants decreased in order of Calligomum mongolicum, Reaumuria soongorica and Nitraria tangutorum from MDA and O2-..The effect of Calligomum mongolicum to clean the active oxygen molecule by improving the activityof super oxide dismutase (SOD) , catalase (CAT) was much more remarkable than Reaumuria soongorica and Nitraria tangutorum. While the effect of peroxide enzyme (POD) was not remarkable to protect the plants under the drought stress. The drought resistant capability of three desert plants decreased in order of Reaumuria soongorica, Nitraria tangutorum and Calligomum mongolicum from SOD and CAT. Chlorophyll content of Reaumuria soongorica and Nitraria tangutorum were decreased because the soil drought stress.While chlorophyll content of Calligomum mongolicum was increased under the same condition .It showed that Calligomum mongolicum was tardied to the changing of water.5. The results showed that the drought resistant capability of Reaumuria soongorica from different area decreased in order of WWM﹥JQJ﹥ZYL﹥LZJ, the drought resistant capability of Nitraria tangutorum from different area decreased in order of JQJ﹥WWM﹥ZYL﹥LZJ,the drought resistant capability of Calligomum mongolicum from different area decreased in order of JQJ﹥WWM﹥ZYL.We could see that the more drought stress the more drought resistant capability of desert plants, it was the result that plants adapted to environmental condition through adjusting their physiological changing.6. Eighteen drought resistant indexes were restricted and relyed on each other in the drought resistant mechanisms of three plants, and they adjusted the inner drought resistant mechanisms comprehensively. While three mechanisms such as increasing WUE through declining Tr, the xanthophyll cycle-dependent thermal energy dissipation and osmoregulation matters relying on mainly on Pro occupied important place in the drought resistant mechanisms of Reaumuria soongorica. The xanthophyll cycle-dependent thermal energy dissipation and the photoprotective mechanism of photoinhibition played leading roles in the drought resistant mechanisms of Nitraria tangutorum. The drought resistant mechanisms of Calligomum mongolicum was complicated more than other plants,because chlorophyll adjusting and enzyme ability of SOD and CAT mechanisms which were not important in other plants played important roles in Calligomum mongolicum, at the same time, it adapted to the double drought stress of soil and air through higher ability of holding and saving water and WUE.更多还原