【作者】 米银法；

【导师】 马锋旺；

【作者基本信息】 西北农林科技大学 ， 果树学， 2009， 博士

【摘要】 氧是线粒体电子传递链的末端受体,是高等植物正常生理代谢和生长发育必不可少的条件。但植物生长发育过程中经常会遭受土壤雨涝积水、灌溉不均和土壤质地紧实等因素,造成土壤通气受阻,氧气浓度降低,导致植物根际缺氧。猕猴桃属藤本类植物,原产于我国,是一类营养价值高、经济效益大的新兴广泛栽培的重要果树之一。但生产中,猕猴桃不耐涝,其砧木常因季节性降雨不均、水肥管理不当而缺氧遭受根际低氧胁迫。本文以10个猕猴桃种和品种的实生苗为试材,采用营养液水培通氮气低氧或淹水处理的方法,研究了猕猴桃根际耐低氧能力的种间差异,并从中选择差异较大的两种实生苗即:耐低氧的美味猕猴桃‘秦美’（Actinidia deliciosa）和低氧敏感的中华猕猴桃‘红阳’（Actinidia chinensis）为试材,研究了猕猴桃对低氧胁迫响应的种间差异机理,旨在为猕猴桃栽培与水肥管理和抗逆育种提供理论依据和指导。主要研究结果如下:1.根际低氧胁迫下,所有供试猕猴桃植株的生长都受到了不同程度的抑制。低氧处理11 d后,猕猴桃幼苗新生根长、株高、生物量、根系活力、叶片生长速度、叶绿素含量、叶绿素a/b均低于对照。猕猴桃叶、根MDA和RMP相对增加,而根内MDA含量增加幅度高于叶片。不同种猕猴桃各指标降低或升高的幅度不同,表明对低氧胁迫响应的敏感程度也不同。2.用隶属函数及聚类分析法,对10种猕猴桃耐低氧能力综合评价。结果表明10种供试猕猴桃耐低氧能力可以分为三个级别:一级为耐低氧型猕猴桃（‘海沃德’猕猴桃、‘秦美’猕猴桃、‘金香’猕猴桃、阔叶猕猴桃、‘华优’猕猴桃）;二级为中等耐低氧型猕猴桃（‘西选’猕猴桃、毛花猕猴桃、金花猕猴桃、山梨猕猴桃）;三级为不耐低氧（敏感）型猕猴桃（‘红阳’猕猴桃）。3.低氧胁迫下,猕猴桃幼苗生长受到抑制,植株鲜、干重均低于对照。抗性强的美味猕猴桃生长受影响相对较小,表现出一定的耐性。同时叶、根内源ABA含量增加。叶内IAA含量先升高后下降;根内IAA含量变化与叶类似。叶、根内GA3和ZR随胁迫时间延长而降低。根和叶内IAA/ABA、ZR/ ABA、GA3/ABA比值均呈现下降趋势。猕猴桃幼苗抗低氧能力与内源激素的平衡调节机制密切相关。4.低氧胁迫下,猕猴桃幼苗净光合速率明显受到抑制,上午10:00只出现一次小高峰,之后明显降低,13:00左右出现负值,表明叶片光和能力受到严重抑制;气孔导度随胁迫时间的延长明显降低;而蒸腾速率先升后降;胞间CO2浓度呈明显的W型,较对照显著增加。随胁迫天数的增加,叶片F0、F0′、qN、Hd逐渐升高;Fm、Fv、Fv/Fm、Fv/F0、Fv′/ Fm′、qP、Pc、ETR逐渐降低;Ex先升后降。PSⅡ吸收光能用于天线热耗散的百分率逐渐升高,用于光化学反应的能量百分率前3d内基本稳定,之后显著降低。而PSⅡ反应中心非光化学能量耗散百分率（Ex）则先升后降。表明胁迫前3d,猕猴桃PSⅡ吸收光能用于叶绿素荧光能量的分配没有受到影响。但5d后进入PSⅡ反应中心的能量减少,通过天线热耗散的能量增多,说明猕猴桃在遭受低氧胁迫时,幼苗叶片光化学效率明显降低,但一定程度上可通过非光化学猝灭耗散能量,来保护光合机构免遭破坏。5.随根际低氧胁迫时间的延长,美味和中华猕猴桃叶、根内SOD、POD和CAT活性前期增强后期降低,O₂^·|-、H₂O₂、MDA含量增加;RMP增大,耐低氧的美味猕猴桃活性氧增加速度明显低于中华猕猴桃,抗氧化酶活性增加幅度明显高于中华猕猴桃;相同胁迫下,同种猕猴桃叶和根内抗氧化酶活性最大值出现的时间和增加幅度不同。表明抗低氧能力强的猕猴桃有较强的抗氧化保护系统;叶和根对低氧胁迫的感受和适应机理不同。6.低氧胁迫下,猕猴桃幼苗根系无氧呼吸代谢增强。与对低氧敏感的中华猕猴桃相比,耐低氧能力较强的美味猕猴桃根内PDC、ADH、G-6PDH及乙醇含量的增加幅度较大;但LDH活性、乳酸、乙醛和丙酮酸含量的增加幅度较小。MDH含量在整个胁迫过程中均呈下降趋势。无氧呼吸代谢能力的差异可能是猕猴桃种间耐低氧能力差异的主要生理机制。7.根际低氧胁迫下,猕猴桃幼苗叶和根内大量营养元素N、P、K、Mg、Ca及微量元素Fe、Cu、Zn含量降低;而Mn含量增加。抗性强的幼苗叶、根内大量元素P、K、Ca吸收受到的影响明显低于抗性弱的猕猴桃,而N、Mg含量降低幅度无显著差异。说明P、K、Ca可能是引起两猕猴桃抗性差异的主导营养物质因素。Zn、Fe、Cu的吸收虽然也显著降低,但抗性弱的猕猴桃幼苗受到的影响相对较大。同时根际低氧胁迫下,猕猴桃幼苗对同种元素的吸收,叶与根之间还存在着显著的差异,根比叶降低幅度大的有P、K、Mg、Zn。叶降低幅度比根大的有Ca、Fe、Cu。Mn的吸收根的增幅高于叶。更多还原

【Abstract】 Molecular oxygen is the terminal electron acceptor in the mitochondrial electron transport chain and is also the prerequisite conditions that are required by higher plants during their growth and development. However, shortage of oxygen or anoxia is a common environmental challenge which plants have to face throughout their life.Floods and excess of rainfall are examples of nature conditions that lead to root hypoxia or anoxia.Low oxygen concentration can also be a normal attribute of a plant natural environment. The kiwifruit （Actinidia deliciosa） is a large, woody, deciduous vine that was native to the Yangtze Valley of China. Now it is widely planted as a burgeoning commercial planting fruit tree around the world because of its abundant nutrient value. Nevertheless, kiwifruit plants’rootstocks are very sensitive to water flooding or excess of rainfall, which can easily produce root-zone hypoxia stress and reducing conditions, which can damage the plants metabolism. Therefore, hypoxia stress is incidental to the kiwifruit plants during growing season.In this thesis, 10 kinds of kiwifruit seedlings were treated with hydroponics hypoxia or waterlogging to study their root-zone hypoxia tolerance. The experiment seedlings were subjected to hypoxia by ?ushing nutrient solution with N2 gas （99.99% N2） or waterlogging for 11days. The nutrient solution of control plants was continuously ?ushed with air under an air pump. Oxygen concentration in the vessels was monitored with an oxygen meter. Hypoxia-tolerance kiwifruit seedling‘Qinmei’（Actinidia deliciosa） and hypoxia-sensitive seedling‘Hongyang’（Actinidia chinensis） were selected as experimental materials to study their physiological response differences. The physiology and biochemical mechanism of hypoxia stress on the seedlings were discussed, all above provided the theoretic base and technical guideline for kiwifruit cultivation, soil management and resistive breeding. The results were as follows:1. Growth of all kiwifruit seedlings were inhibited to various degrees under root-zone hypoxia stress. After 11 days waterlogging hypoxia treatment,the max length of new root, plant height, plant biomass about leaves and roots, root activity, relative growth rate of leaves, content of chlorophyll and chlorophyll a/b in leaves under root-zone hypoxia stress obviously declined comparing with control. MDA content, relative conductance in the leaves and roots all increased in 16 kiwifruits. But MDA content and relative conductance in roots was much higher than those of leaves. The sensitivities of 10 kiwifruit seedlings to hypoxia stress were obviously different.2. With the method of subordinate function and cluster analysis, the adversity resistance coefficient （including 6 physiological and 5 growing indexes） of 10 kiwifruit seedlings, were comprehensively evaluated in order to appraise their hypoxia-tolerance abilities. According to the results,‘Hayward’,‘Qinmei’,‘Jinxiang’,‘Kuoye’,‘Huayou’kiwifruit seedlings held higher tolerance to root-zone hypoxia stress, while‘Hongyang’kiwifruit seedlings was sensitive to root-zone hypoxia stress.The others including‘Xixuan’,‘Maohua’,‘Jinhua’,‘Shanli’kiwifruit seedlings kept moderate resistant intensity to root-zone hypoxia stress.3. Under root-zone hypoxia stress, the fresh and dry weights of seedlings treated under hypoxia were less than those of control. Effects of hypoxia stress on A. deliciosa were much slighter than on A. chinensis, which made A. deliciosa perform a better resistance. The ABA contents in A. deliciosa, A. chinensis leaves and roots were enhanced obviously. The IAA contents in A. deliciosa, A. chinensis leaves were raised to the maximum on the 7th day, then reduced but still higher than those of control. Same tendencies happened in the roots of both species, but the peak appeared on the 5th day and differed from that of the leaves. The GA3 and ZR contents in A. deliciosa, A. chinensis leaves and roots were decreased. The ratios of IAA/ABA, ZR/ABA and GA3/ABA were also studied and the results of them decreased, which showed that kiwifruit seedlings were obviously inhibited from growing under hypoxia and the resistant ability had an intimate relationship with endogenous hormones.4. Under Under waterlogging stress, daily net photosynthetic variation rate in leaves of A. deliciosa kiwifruit seedlings was restrained. Compared with control, only one peak was observed at 10:00 and then reduced evidently. At about 13:00, the quantitative data of Pn presented less than zero, which showed the leaves’capability of photosynthesis was destroyed badly and could not keep the capability of photosynthesis.The stomatal conductance was reduced, too.Transpiration rate of kiwifruit seedlings raised to the maximum at 10:00, then reduced but lower than that of control in daily time. Intercellular CO2 rate in daily time presented a‘W’shape and raised evidently. With the prolonged waterlogging stress, F0、F0′、qN、Hd of the leaves raised gradually and the Fm、Fv、Fv/Fm、Fv/F0、Fv′/ Fm′、qP、Pc、ETR dropped evidently. Ex raised firstly and then reduced evidently. The percentages of the antenna heat dissipation raised. The percentages of the photochemistry kept stably in the first 3 days and after 5 days, decreased.5. Under hypoxia stress, the activities of SOD, POD, and CAT were all stimulated and increased greatly in leaves and roots. The raise rate and activity peaks of SOD, POD, CAT in leaves and roots of A. deliciosa were higher than those of A. chinensis. The contents of H₂O₂, O₂^·|- , MDA, RMP in leaves and roots under hypoxia stress increased significantly. However, the increase ratio and peak contents of H₂O₂, O₂^·|- , MDA in leaves and roots of A. deliciosa were much lower than those of A. chinensis. On the tendency and peak time of SOD, POD, CAT, H₂O₂, O₂^·|- , MDA, there were also striking differences between them. So, much resistant kiwifruit species had advantageous anti-active oxygen systems, which could scavenge free radicals effectively to avoid injuring the membrane lipid. When facing hypoxic stress, leaves and roots had also different responses and adjusting mechanisms.6. The results showed that root-zone hypoxia accelerated the anaerobic respiration of kiwifruit seedlings’roots. Under root-zone hypoxia stress, the increment of LDH activity and aldehyde, lactate, pyruvate contents were lesser in A. deliciosa seedlings roots than in A. chinensis, but conversely, the increment of PDC, ADH, G-6-PDH activities and alcohol content in A. deliciosa seedlings roots were higher than those of A. chinensis. It was concluded that the acceleration of alcohol fermentation were in favor of the enhancement of root-zone hypoxia tolerance of kiwifruit seedlings’roots. In all process of the stress, MDH activities reduced at all times, which showed that it was not the key enzyme to adjust the resistance.7. Under root-zone hypoxia stress, macronutrients contents N, P, K, Mg, Ca and micronutrients contents Fe, Cu, Zn in leaves and roots of kiwifruit seedlings reduced significantly. However content of Mn increased and the increase in roots was much higher than that of leaves. Reduce ranges of P, K, Ca upon A. deliciosa were much lower than those of A. chinensis seedlings and reduce ranges of N, Mg had no difference between two kinds of kiwifruit seedlings. Maybe P, K, Ca nutrients were the dominant factors that caused the different resistance between A. deliciosa and A. chinensis. But reduce ranges of Zn, Fe, Cu upon A. chinensis were much lower than those of A. deliciosa seedlings. So far as the same nutrient was concerned, there were also much significant differences between leaves and roots. Reduce ranges of P, K, Mg, Zn upon roots were much higher than those of leaves. However, reduce ranges of Ca、Fe、Cu upon roots were much lower than those of leaves.更多还原