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干旱下植物根际促生菌对苹果实生苗生理特性和磷吸收利用的影响

Effects of Plant Growth-promoting Rhizobacteria on Physiological Characteristics and Phosphorus Uptake and Utilization of Apple Seedlings under Arid Environment

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【Author in Chinese】 张超

【Supervisor】 张海张立新

【Author's Information】 西北农林科技大学, 环境工程, 2017, 硕士

【Abstract in Chinese】 通过转入外源基因或者接种人工合成菌剂来提高植物在干旱环境中的适应能力,是近年来国内外研究的热点。植物根际促生细菌(PGPR)是指生存在植物根圈范围中,对植物生长有促进或对病原菌有拮抗作用的有益细菌。国内外对PGPR的研究主要集中在促进植物生长、活化土壤养分、减少化肥施用、提高植物诱导系统抗性等方面,但有关苹果抗逆性方面的研究较少。本研究中,我们利用盆栽试验,将从黄土高原地区旱地果园根系周围分离筛选出的1株既具有ACC脱氨酶活性又具有溶磷能力的根际促生菌“YX2(Psdeuomnoda fluoerncne)”接种于“八棱海棠”苹果实生幼苗根际周围,通过设置4个不同的干旱胁迫梯度(正常水分、轻度干旱、中度干旱和重度干旱),研究接种YX2对苹果幼苗的抗旱生理以及活化吸收土壤中磷元素的影响。其主要研究结果如下:(1)随着干旱胁迫程度的增加,幼苗的叶片相对含水量和叶绿素含量逐渐降低,叶片相对电导率逐渐升高。接种YX2可提高叶片相对含水量和叶绿素含量,且在干旱环境下可显著降低叶片相对电导率。干旱降低了苹果的光合速率(Pn)和气孔导度(Tr),接种YX2可提高Tr,缓解干旱胁迫对Pn的抑制,且在中度干旱下,缓解效果最为显著,其Pn和Tr分别较未接种处理提高6.80%和15.00%。接种YX2可抑制干旱胁迫下幼苗最大光化学效率、实际光化学效率和光化学猝灭系数的降低,抑制初始荧光和非光化学猝灭系数的升高,在中度干旱下整体效果最佳。(2)正常水分处理下,接种YX2对叶片抗氧化酶(过氧化氢酶、过氧化物酶、超氧化物歧化酶)、渗透调节物质(脯氨酸、可溶性糖、可溶性蛋白)和膜脂过氧化产物(丙二醛)的影响较小;随着干旱胁迫强度的增加,接种YX2可不同程度增加抗氧化酶活性,降低渗透调节物质和丙二醛的积累,且在中度干旱下,YX2的接种效应最显著。(3)运用主成分分析和隶属函数法对干旱胁迫下不同处理的幼苗抗旱能力进行综合评价。主成分分析表明,不接种处理下,主成分1和主成分2中得分系数最高的指标分别为丙二醛和蒸腾速率;接种YX2处理下,主成分1和主成分2中得分系数最高的指标亦分别为丙二醛和蒸腾速率,说明接种YX2处理对主要成分的贡献率影响不大。隶属函数分析表明,无论处于何种水分状态,接种YX2处理都影响了幼苗的抗旱性,即接种YX2处理下幼苗的平均隶属函数值更高,且在轻度和中度干旱下增幅显著,分别较未接种处理提升9.19%和10.12%,从而使幼苗具有更强的抗旱性。(4)接种YX2提高了幼苗植株干物质生物量、植株全磷含量、根系酸性磷酸酶活性、土壤速效磷含量以及土壤碱性磷酸酶活性,降低了土壤全磷含量。不同水分下YX2吸磷贡献率表现为中度干旱>正常水分>轻度干旱>重度干旱,YX2吸磷贡献率与根系酸性磷酸酶、土壤速效磷和土壤碱性磷酸酶呈正相关关系。(5)接种YX2促进了幼苗根系的生长,提高了根系活力,其中根系总长度和根系活力在轻度干旱下显著增加。本研究测定了根系分泌物中5种有机酸(草酸、苹果酸、酒石酸、丁二酸和柠檬酸)的含量,接种YX2增加了根系分泌有机酸的总量,不同水分条件下比未接种处理增加0.0120.035 mg·L-1·2h-1,其中草酸泌量占到了有机酸总量的50%左右。接种YX2同时也增加了分泌物中氨基酸和可溶性总糖的含量,这些分泌物的增加有助于改善根际土壤生态环境。本研究揭示了具有溶磷能力的根际促生菌YX2对干旱胁迫下苹果实生幼苗的抗旱生理以及对土壤中磷元素吸收利用的影响机制,得出了在轻度或者中度干旱环境下YX2的接种效应较好,这为在干旱或半干旱地区利用PGPR与植物互作提高植物的抗旱性以及养分利用能力提供了新的研究思路和技术手段。

【Abstract】 It is a hotspot to study the adaptability of plants in arid environment by transforming foreign genes or inoculating synthetic bacteria in recent years.Plant growth-promoting rhizobacteria(PGPR)refers to beneficial bacteria that survive in the plant root circle and have a promoting effect on plant growth or antagonism to pathogens.The research on PGPR at home and abroad mainly focused on promoting plant growth,activating soil nutrients,reducing chemical fertilizer application and improving plant inducing system resistance,but there are few studies on apple resistance.In present study,we isolated a rhizosphere-promoting bacteria named YX2(Psdeuomnoda fluoerncne)from the rhizosphere of dryland orchards in the Loess Plateau,which had both ACC-deaminase activity and phosphate dissolved ability.By using pot experiments,we inoculated YX2 to ‘octagonal Begonia’ apple seedling rhizosphere,and four different drought stress gradients(normal water,light drought,moderate drought and severe drought)were set up by controlling soil moisture to study the effects of inoculating YX2 on drought resistance of apple seedlings and activating absorption of phosphorus in soil.The main results are as follows:(1)With the increase of drought stress,the relative water content and chlorophyll content of leaves of seedlings decreased gradually,the leaf relative conductivity increased gradually.Inoculating YX2 could increase the relative water content and chlorophyll content of leaves and significantly decrease leaf relative conductivity in arid environment.Drought stress reduced the photosynthetic rate(Pn)and stomatal conductance(Tr)of apple seedlings.Inoculation of YX2 could increase Tr and alleviate the inhibition of drought stress on Pn,and alleviating effect was significant under moderate drought,whose values of Pn and Tr enhanced by 6.80% and 15.00%,respectively,compared with the non-inoculation treatment.Inoculation of YX2 could inhibit the decrease of maximum photochemical efficiency,actual photochemical efficiency and photochemical quenching coefficient of seedlings under drought stress,and inhibit the increase of initial fluorescence and non-photochemical quenching coefficient,and the best overall effects were under moderate drought.(2)Under normal water treatment,the effects of inoculating YX2 on antioxidant enzymes(catalase,peroxidase,superoxide dismutase),osmotic adjustment substances(proline,soluble sugar,soluble protein)and membrane lipid of leaves were less.With the increase of drought stress,the inoculation of YX2 could increase the activity of antioxidant enzymes and reduce the accumulation of osmotic regulators and malondialdehyde at different extent,and the effect of YX2 was the most significant in moderate drought.(3)The drought resistance of seedlings under different drought stress was evaluated by principal component analysis and membership function method.The results of principal component analysis showed that the highest score of the main component 1 and the main component 2 were malondialdehyde and transpiration rate respectively under the non-inoculation treatment.Under the YX2 treatment,the highest score of the main component 1 and the main component 2 were malondialdehyde and transpiration rate,respectively,which indicated that inoculation of YX2 treatment had little effect on the contribution rate of main component.The results of subordinate function analysis showed that the YX2 treatment affected the drought resistance of seedlings.The average membership value of the seedlings under the YX2 treatment was higher than no inoculation treatment no matter what kind of moisture state,and the increase was significant in the light and moderate drought,increased by 9.19% and 10.12% compared with non-inoculation treatment,respectively,so that seedlings had stronger drought resistance.(4)No matter what water conditions,inoculation of YX2 treatment increased the dry matter biomass and total phosphorus content of seedlings,enhanced apple root acid phosphatase activity,soil available phosphorus content and soil alkaline phosphatase activity,and decreased soil total phosphorus content.The contribution rate of YX2 absorbing phosphorus of under different water conditions was ranking that moderate drought> normal water> light drought> severe drought.The contribution rate of YX2 absorbing phosphorus was positively correlated with root acid phosphatase,soil available phosphorus and soil alkaline phosphatase.(5)Inoculation of YX2 promoted the growth of seedling roots and increased the root vigor,the total root length and root activity were significantly increased under light drought.In this study,the contents of five organic acids(oxalic acid,malic acid,tartaric acid,succinic acid and citric acid)in root exudates were determined.Inoculating YX2 increased the content of organic acids in roots,and increasing by 0.012 0.035 mg·L-1·2h-1.Oxalic acid is main secretion,whose amount accounted for about 50% of the total secretions.Meantime,inoculation of YX2 also increased the contents of amino acids and soluble total sugar in the secretions.The enhancement of these secretions could improve the soil rhizosphere ecological environment.In this study,we investigated the effecting mechanism of rhizosphere-promoting bacteria YX2 with phosphate dissolved ability on the drought-resistant physiology of apple seedlings and the absorption and utilization of phosphorus in soil under drought stress.The results showed that the overall effect of YX2 inoculation was better in light or moderate arid environment,which provided new ideas and techniques for improving the drought resistance and nutrient utilization of plants by using PGPR interacting with plants in arid or semi-arid areas.

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