【作者】 赵宽；

【导师】 吴沿友；

【作者基本信息】 江苏大学 ， 农业生物环境与能源工程， 2014， 博士

【摘要】 环境胁迫下,植物通过自身调节适应环境,形成了多种适应性机制,如光合作用机制,无机营养利用机制,碳酸酐酶作用机制等等。其中植物根系分泌的有机酸组成和含量的变化也是植物应对环境胁迫的一种重要的适应性机制。根系分泌的有机酸主要来源于光合作用固定的碳,其通过一系列复杂的生物化学作用,直接影响根际区域养分的获取,重金属的解毒和微生物活性等根际活动,从而影响植物的生长发育状况。因此,根系分泌的有机酸在植物逆境生理中起着至关重要的作用。本文选择了喀斯特适生植物构树和诸葛菜作为研究对象,以非适生植物桑树和油菜作为对照,设置人工模拟喀斯特环境(高pH,高浓度重碳酸盐,低营养,干旱)的实验,研究了逆境条件下四种植物的光合响应特征,以及有机酸累积和根系有机酸的分泌特征,阐明了其响应机制以及根系分泌有机酸的来源；探讨了长期胁迫下四种植物的光合特征及根系有机酸的分泌特征,为选择环境适应性植物提供了证据,提出了一种应用根系有机酸的分泌特征表达植物抗逆性的方法。本研究对于了解逆境条件下根系分泌物、光呼吸活性与植物需水和需肥量之间的关系具有重要意义,为后续研究根系分泌物对逆境生理响应特点,发掘作物自身水肥调控的潜能提供了研究基础；以期真正实现节水灌溉以及精准施肥的目的,本研究在农业工程领域为节水灌溉和精准施肥中提供了初步的研究基础。本实验的研究结果如下：(1)研究了四种植物的光合响应特征。测定了不同锌(含锌(0.02mM),缺锌(0mM))与碳酸氢根离子(0mM和10mM碳酸氢根离子))交互处理下四种植物的生长参数、光合参数、叶绿素荧光参数和叶绿素含量,结果表明不同植物对锌与碳酸氢根离子处理下的光合响应模式不同。其中,构树的光合碳代谢及无机碳利用能力最强。构树对缺锌、高碳酸氢根离子以及两者交互逆境适应性最强；诸葛菜和桑树次之；油菜的PSⅡ光反应中心受到的破坏最大,其适应能力也最弱。(2)研究了四种植物有机酸的分配、转运和根系有机酸的分泌特征。在人工模拟缺锌和高浓度碳酸氢根离子逆境下,测定植物器官(根、茎、叶)以及根系分泌的有机酸含量,分析植物有机酸的分配、转运和分泌特征。结果表明,叶片是植物体有机酸的主要产生区域,根、茎、叶以及根系分泌的有机酸的来源不同。叶片中的有机酸主要来源于三羧酸循环和乙醛酸循环,而其他器官以及根系分泌的有机酸主要来源于三羧酸循环。在有机酸形成、分配、转运和分泌的过程中,草酸和柠檬酸受到的影响最大。(3)研究了四种植物光合参数和叶绿素荧光参数的动态变化特征。在人工模拟不同锌(含锌(0.02mM),缺锌(0mM))与碳酸氢根离子(0mM,1mM,5mM,10mM碳酸氢根离子))交互处理的逆境下,随着处理时间的变化,四种植物的光合作用、叶绿素荧光参数及叶绿素含量的变化趋势均不同。四种植物都能适应低浓度碳酸氢根离子(1,5mM)的环境。对缺锌和高碳酸氢根离子(10mM)环境的长期适应能力,构树和诸葛菜强于桑树和油菜。(4)研究了四种植物根系分泌有机酸的动态变化特征。在人工模拟不同锌(含锌(0.02mM),缺锌(0mM))与碳酸氢根离子(0mM,1mM,5mM,10mM碳酸氢根离子))交互处理的逆境下,随着处理时间的增加,根系分泌的草酸、柠檬酸、苹果酸、丁二酸和酒石酸的含量都增加。含锌的情况下,所有的碳酸氢根离子处理都促进了四种植物根系有机酸的分泌,同一时期下,5,10mM碳酸氢根离子处理的植物根系分泌的有机酸含量较高,尤其是草酸,柠檬酸和苹果酸；缺锌的情况下,随着处理时间的增加,碳酸氢根离子并未显著抑制四种植物根系有机酸的分泌。(5)研究了植物根系有机酸的磷提取成本特征,并提出了一种利用磷提取成本表达植物抗缺磷能力的方法。测定了缺磷逆境下四种植物根系分泌的草酸,柠檬酸和苹果酸含量。建立草酸、柠檬酸和苹果酸的标准溶液与根系土壤磷提取的模型,从而得到植物根系分泌的有机酸对根际土壤磷提取的能力。并结合根系分泌的草酸、柠檬酸和苹果酸的有机碳摩尔损失量,提出了根系分泌的有机酸对根际土壤磷提取成本(Pex-cost)的概念,并将该概念应用于表征植物抗缺磷逆境的能力,结果表明四种植物磷提取成本为诸葛菜≈构树<桑树<油菜,这说明诸葛菜和构树抗缺磷能力较强。(6)建立植物叶片的叶绿素荧光参数与根系分泌的有机酸之间的联系。在缺磷处理下,植物叶片的叶绿素荧光参数(Fo, Fv/Fm)与根系分泌苹果酸的含量具有线性关系,确定了利用根系分泌苹果酸表达植物抗逆性的方法；并将该方法应用于植物抗旱性的表达,结果表明构树和诸葛菜的抗旱性强于桑树和油菜。综上所述,我们主要探讨了模拟喀斯特逆境下,长期处理和短期处理对不同植物的光合响应特征及根系有机酸的分泌特征,分析了根系分泌有机酸的来源。并提出了利用根系分泌的有机酸特征表达植物抗缺磷逆境能力和抗干旱能力的方法,为抗逆性植物的选择提供了强有力的证据。更多还原

【Abstract】 Under environmental stress, plants have many adaptation mechanisms by autogenously regulation such as photosynthetic response mechanism, mechanism of inorganic nutrition utilization, mechanism of carbon anhydrase function and others. While variation of the amount of root-exuded organic acids, derived from the photosynthetic fixed carbon, was an important adaptive mechanism of plant response to environmental stress. Through a series of complicated biochemical effect, organic acids of root exudations direct influenced many rhizosphere processes such as the nutrient acquisition in rhizosphere region, detoxification of heavy metal and microorganism, and then the plant growth and development were affected. Therefore, the root-exuded organic acids played a vital role in plant stress physiology.The study selected plant species adaptability to Karst----Broussonetia papyrifera (B. papyrifera) and Orychophragmus violaceus (O. violaceus) as the research objects, and the none Karst adapted plant species----Morus alba (M. alba) and Brassica napus (B. napus) as the control. By setting the artificial simulation of Karst environment (high pH, high bicarbonate concentration, low nutrition, drought), we explored the response mechanism of photosynthesis, and organic acids accumulation in plants and the root organic acids exudation, illuminated the source of organic acids in root exudations, discussed the characteristics of photosynthetic and root organic acids exudation under the long-term environmental stress, presented a method of expressing plant resistance to stress by root organic acid secretion characteristic. All of this results provided evidences for selecting plant adaptability to difference environment. This study had a great significance to understand adversity under the condition of root secretion, light respiration activity and plant water requirement and the relationship between the fertilizer requirements, provides a research basis for follow-up study of root secretion of adversity physiological response characteristics, potential of the excavation of the relationship between crop itself. In order to achieve the purpose of water-saving irrigation and precise fertilization, this research provides a preliminary research basis of precise fertilization and water-saving irrigation in the field of agricultural engineering.The experimental results are as following:(1) We studied the photosynthetic response mode of four plant species under interaction of Zn treatments (Zn-sufficient,0.02mM; Zn-deficient,0mM) and bicarbonate treatments (0mM and10mM bicarbonate). By measurement of the growth parameters, photosynthetic parameters, chlorophyll fluorescence parameters and chlorophyll content under Zn deficiency, or high bicarbonate concentration, or both. The results showed the photosynthetic response mode varied with species. Among the four plant species, B. papyrifera showed greatest adaptability to bicarbonate treatment, low Zn, or both, which resulted from the greatest of inorganic carbon assimilation and photosynthetic carbon metabolism in B. papyrifera; B. napus was sensitive to low Zn, bicarbonate treatment, or both, owing to the greatest damage in photosystem Ⅱ reactive center; the adaptability of O. violaceus and M. alba were between B. papyrifera and B. napus.(2) We studied the characteristics of allocation, transportation of organic acids in plant organs and root organic acids exudation. By artificial simulation of zinc treatments (Zn-sufficient,0.02mM; Zn-deficient,0mM) and bicarbonate stress (0mM and10mM bicarbonate), we investigated the amount of organic acids in plant organs (root, stem and leaf) and the amount of root-exuded organic acids, and reflected the characteristics of organic acids allocation, transportation and exudation. The results indicated that leave was the main region of organic acid production; the source of organic acids of root, stem, leave and root exudations was different, the source of organic acids of leave was main from Krebs cycle and glyoxylate cycle, the source of organic acids of root, stem and root exudations was main from Krebs cycle. Oxalic and citric acids are suffered the greatest influence in formation, allocation, translocation and exudation of organic acid.(3) We studied the dynamic variation characteristics of photosynthetic parameters, chlorophyll fluorescence parameters. Under the artificial simulation of interaction of zinc treatments (Zn-sufficient,0.02mM; Zn-deficient,0mM) and bicarbonate stress (0mM,1mM,5mM,10mM bicarbonate), the four plant species showed the difference variation of photosynthetic parameters, chlorophyll fluorescence parameters and chlorophyll content during the treatment time duration. The four plant species can adapt the environment of low bicarbonate concentration (1,5mM). Under the dual influence of Zn deficiency and excessive bicarbonate concentration (10mM), the adaptability of B. papyrifera and O. violaceus was greater than that of M. alba and B. napus under the long-term treatment.(4) We studied the dynamic variation characteristics of root-exuded organic acids. Under the artificial simulation of interaction of zinc treatments (Zn-sufficient,0.02mM; Zn-deficient,0mM) and bicarbonate stress (0mM,1mM,5mM,10mM bicarbonate), the amount of oxalic, citric, malic, succinic, and tartaric acids were depended on plant species and nutrition concentration during the treatment time duration. Under Zn-sufficient conditions, all three bicarbonate treatment stimulated root organic acids exudation in four plant species, the root-exuded organic acids was increased, particularly oxalic, citric, malic acids, under the5,10mM bicarbonate treatments at the same treatment time. Under Zn-deficient conditions, bicarbonate had no significant inhibition the exudation of root organic acids of four plant species during the treatment time duration.(5) We studied the characteristics of P-extraction cost by root-exuded organic acids in four plant species, and indicated a new method of expressing plant resistance to P deficiency stress by utilizing P-extraction cost. The amount of oxalic, citric and malic acids was measured in four plant species under P deficiency stress, and the models of the standard solution of oxalic, citric, and malic acids and the rhizosphere soil P extraction were established, and then the P-extraction of root-exuded organic acids was calculated. And we calculated the organic carbon loss of root-exuded oxalic, citric and malic acids. Therefore, we presented the concept of P-extraction cost by combining P extraction and organic carbon in root-exuded organic acids, and applied this expressed the plant resistance to P deficiency stress. The results showed the resistance to P deficiency stress of four plant species was the following series:O. violaceus≈B. papyrifera<M. alba<B. napus, which indicated that O. violaceus and B. papyrifera have the greater resistance to P deficiency stress.(6) We established the relationship between the chlorophyll fluorescence parameters and root-exuded organic acids. Under phosphorus stress, the linear relationship was between the chlorophyll fluorescence parameters (Fo, Fv/Fm) and the amount of root-exude malic acid, and founded a low-cost method was used for assessing plant adaptability to a low-phosphorus environment when no chlorophyll fluorescence instrument was available. And the method directly applied in the expression of drought resistance, the results showed that the drought resistance of B. papyrifera and O. violaceus was greater than that of M. alba and B. napus.In summary, we discussed the photosynthetic response characteristics and root organic acids exudations characteristics of four plant species in the long-term and short-term treatment under the simulation of Karst environment; and analyzed the source of organic acids in root exudations, and presented the method of expressing plant resistance to P deficiency and drought stress by the characteristics of root organic acids exudations, which provided strong evidence for plants resistance to stress.更多还原