【作者】 王玉凤；

【导师】 王庆祥；

【作者基本信息】 沈阳农业大学 ， 作物栽培学与耕作学， 2008， 博士

【摘要】 本研究对不同浓度NaCl胁迫下玉米幼苗的干重、渗透调节物质含量、保护酶活性、各器官离子的吸收与运转等生理生化特性进行研究,分析并探讨了盐胁迫对玉米幼苗的伤害及其耐盐机制,为进一步在分子水平上深入研究玉米耐盐性奠定了基础。同时,在盐胁迫下,施用适量的外源物质钙、钾、磷、硅和NO供体硝普钠（sodium nitroprussideSNP）,分析了其对玉米幼苗生理生化特性的影响,探讨了外源物质提高玉米耐盐性的作用机理,为提高植物的耐盐性提供一定的理论依据。主要研究结果如下:1盐胁迫对玉米幼苗的伤害及其耐盐机制盐分胁迫包括渗透胁迫和离子胁迫,渗透胁迫导致吸水困难,离子胁迫造成生物膜破坏和生理紊乱。盐胁迫对玉米幼苗的伤害及其耐盐机理主要有以下几个方面:1.1玉米幼苗具有一定的耐盐性,50mmol·L^-1NaCl胁迫下,玉米幼苗干重略有增加,主要是根系干重显著增加。随着NaCl浓度增加玉米幼苗各器官干重下降,干重下降较大的器官是生长叶和成熟叶叶片。随NaCl浓度增加,各器官的含水量降低,含水量变化幅度为:根系＞生长叶＞成熟叶叶片＞成熟叶叶鞘。1.2 NaCl胁迫导致叶绿素含量降低,其中叶绿素a降低的幅度小于叶绿素b。盐胁迫下玉米幼苗净光合速率、蒸腾速率、胞间CO₂浓度、气孔导度降低,而水分利用率和气孔限制值上升,表明盐胁迫使玉米幼苗光合速率降低主要是由气孔因素引起的。1.3 NaCl胁迫导致玉米幼苗细胞膜受到伤害,随NaCl浓度增加,叶片的电解质渗漏率增加,叶片和根系中MDA含量增加。1.4 NaCl胁迫下,玉米幼苗叶片和根系中可溶性糖、可溶性蛋白、游离氨基酸和脯氨酸含量均增加,但叶片增加幅度大于根系。1.5玉米幼苗在50 mmol·L^-1、100mmol·L^-1NaCl胁迫下,叶片和根系中SOD、CAT、POD活性均增加。但此时叶片和根系中MDA的含量并没有下降,反而增加,说明玉米叶片和根系组织的膜伤害有更复杂的机理。当NaCl浓度达到一定限度后,酶的活性受到抑制,酶活力降低,盐害加重。1.6玉米各个部分Na⁺和Cl^-含量、Na⁺/K⁺和Na^/Ca²⁺比值都是随着培养液中NaCl浓度的增加而迅速提高,Na⁺、K⁺和Cl^-含量的变化幅度是:根系＞成熟叶叶鞘＞生长叶＞成熟叶叶片,玉米幼苗的根系最易受外界离子浓度的影响,叶片受外界环境影响较小。各器官中Ca²⁺、Mg²⁺对盐胁迫的响应不一致,NaCl胁迫使根系中Ca²⁺、Mg²⁺量下降,成熟叶叶鞘中Mg²⁺含量变化规律性不明显;而NaCl胁迫下,成熟叶叶片中Ca²⁺、Mg²⁺含量增加。NaCl胁迫对各器官中的Zn²⁺含量的影响不大。玉米幼苗具有拒Na⁺机制,具有一定的耐盐性,它的耐盐性是根和成熟叶叶鞘来实现的,Na⁺主要贮存在根系和成熟叶叶鞘中,而向成熟叶叶片和生长叶中运输较少。成熟叶叶鞘同时还具有拒Cl^-能力。2外源物质对盐胁迫的缓解作用植物的耐盐性是一种综合机制,其对盐胁迫的适应也是多种多样的,作物的耐盐性是一种相当复杂的生理功能,是遗传特性与外界环境共同作用的结果,不同的外源物质对盐胁迫的缓解作用是通过不同途径实现的,因而很难用某一个指标来说明外源物质与耐盐性的关系。总体上,外源物质对盐害的缓解作用表现在以下几方面:2.1盐胁迫最显著的效应是生长受抑制,本试验中几种外源物质钙、磷、钾、硅和NO在一定浓度下均不同程度的增加了盐胁迫下玉米幼苗的干物质产量。2.2外源物质提高了盐胁迫下叶片中的叶绿素含量,维持了盐胁迫下玉米幼苗较高的光合速率,但不同物质对叶绿素含量的影响不同,例如:外源钾和NO使叶绿素a/b比值增加,而外源磷、硅处理的玉米幼苗绿素a/b比值降低。2.3细胞膜是盐胁迫对植物伤害的原初部位,盐胁迫下细胞电解质渗漏的增加是盐伤害的重要特征之一,适量的外源物质均可降低盐胁迫下玉米幼苗的电解质渗漏率。2.4活性氧清除能力增加。外源钙、磷、钾、硅和NO均可不同程度地增强叶片和根系中SOD、CAT、POD活性,同时使叶片和根系中的膜脂过氧化产物-MDA含量降低。2.5外源物质通过促进盐胁迫下玉米幼苗体内渗透调节物质的运输,使其在叶片和根系中分配更合理,增强了玉米幼苗的渗透调节能力。判断盐胁迫下玉米幼苗渗透调节能力的大小,应看渗透调节物质在叶片和根系中的分配是否合理,单纯叶片中渗透调节物质含量的高低并不能完全说明渗透调节能力的大小。这可能是外源物质提高玉米幼苗耐盐性的一个重要方面。2.6外源钙、磷、钾、硅和NO降低了盐胁迫下玉米幼苗各器官的Na⁺/K⁺和Na⁺/Ca²⁺比值,维持了盐胁迫下玉米幼苗各器官的离子平衡。盐胁迫下外源钙、磷、钾、硅和NO的这些效果是改善玉米幼苗离子吸收与分配、促进生长发育的综合结果,尽管其作用的途径和机理各不相同,但都达到了对盐害缓解的目的,这说明通过外源物质提高植物耐盐性的直接机理不是唯一的。更多还原

【Abstract】 With room water culture experiment, the physiological and biochemical characteristic of maize seedling involved the dry weight, the content of osmotic adjustment, activity of protected enzyme, absorption and transport of ion in different part of maize seedling was studied, Primarily damage and salt tolerance mechanisms of maize seedling under the salt stress was discussed and analyzed . That will provide foundation for the further research Salt tolerance of maize seedling on molecular Level. At the same time, applying proper exogenous substance such as calcium（Ca）, Potassium（K）, phosphorus（P）, silicon（Si） and sodium nitroprusside （SNP）, the effect of physiological and biochemical characteristic was analyzed. The mechanisms of enhance salt tolerance about exogenous substance was discussed, supply definite theory basis for enhance salt tolerance on maize. The main study results was as follows:1. The damage and salt tolerance mechanisms of maize seedling under the salt stressThe salt stress are mainly consist of osmotic stress and ion toxic, osmotic stress could result in difficulty of absorb moisture, the ion stress could result in the biofilms were destroyed and physiological turbulence. The damage and salt tolerance mechanisms of maize seedling can be shown in following main aspects:1.1 maize seedling have definite salt tolerance, under the salt stress (50mmol·^-1NaCl), the dry weight of maize seedling increase little, the dry weight of root increase remarkably. The dry weight of different part of maize seedling decreases along with the increase of salt concentration. The biggish apparatus decreased in dry weight was young leaf and mature leaf. The water content of different parts of maize seedlings decreases along with the increase of salt concentration, the changed extent of the water content are: root＞young blade＞mature blade＞mature sheath.1.2 Salt stress can conduce to the decrease of chlorophyll content; the decrease extent of chlorophyll a is smaller than chlorophyll b. Under the salt stress, the net photosynthesis, transpiration rate, intercellular CO₂ concentration,stomatal conductance of maize seedling decreased, but water use efficiency stomatal limited value of maize seedlings increased.This indicated that the dicrease of photosynthesis of maize seedling under salt stress is the result of stoma factor.1.3 The salt stess can induce the maize seedling Plasma membrane to be damaged, along with the increase of salt concentration, the electrolyte leakage in leaf increases, the content of MDA in leaf and root increase.1.4 Under the salt stress, the content of soluble sugar, soluble protein, free amino acids and proline in leaf and root of maize seedling increased, but the increasing extent in leaf greater than that in root.1.5 When the maize seedling was under the salt stress of 50mmol·L^-1 and 100mmol·l^-1, the activeness of SOD, CAT, POD in leaf and root all increases. But the content of MDA in leaf and root was not decreased on the contrary it was increased. It indicates that the damage of Plasma membrane in maize leaf and root have more complex mechanism. After the concentration of salt attain definite limit, the activeness of enzyme gets to be restrained, the activeness of enzyme decreases, the salt damage aggravated.1.6 The content of Na⁺, Cl^-, Na⁺/K⁺, Na⁺/Ca²⁺ ratio in different part of maize seedling was all rapidly increase along with the increase of salt concentration, the changed extent of Na⁺, K⁺ and Cl^- was: root＞mature sheath＞young blade＞mature blade, the root of maize seedling was influenced most easily by outside ion concentration, the influence on leaf by outside circumstance was on the small side.The response of salt stress on different part of maize seedling was not consistent, it cause the decrease of content of Ca²⁺ and Mg²⁺. The changed disciplinarian of Mg²⁺ content in mature blade is not obvious. But the content of Ca²⁺ and Mg²⁺ increase under the salt stress. The influence on the content of Zn²⁺ is not too. The maize seedling have the mechanism of Na⁺-exclusion and have definite salt tolerance, the salt tolerance was implemented by root and mature sheath, Na⁺ is mainly reserved in root and mature sheath, and the content of Na⁺ was less to be transported to mature blade and young blade. At the same time, mature sheath still have the capacity of Cl^--exclusion.2 Alleviative effect of exogenous substance under salt stressThe salt tolerance of plant is a integrative mechanism, its fit to salt stress was multifarious, the salt tolerance of crop is a kind of complicated physiological mechanism that is the acted together result of genetic characteristic and exoteric condition, the alleviative effect on salt stress caused by exogenous substance was realize through different approach, so it is very difficult to explain the relation of exogenous substance and salt tolerance with a given index. On the whole, the alleviative effect on salt stress caused by exogenous substance manifests as follows:2.1 The growth restrained under salt stress was the most obvious effect, several kinds of exogenous substance such as calcium（Ca）, Potassium（K）, phosphorus（P）, silicon（Si） and NO increased the dry weight of maize seedling at the different extent.2.2 Exogenous substance increased the content of chlorophyll in leaf under salt stress, it keep higher velocity of photosynthesis, but the effect by the different matter is distinct, for example: outer Potassium （K） and NO make the ratio of chlorophyll a/b increased, but outer phosphorus （P） and silicon （Si） make the ratio of chlorophyll a/b decreased in the maize seedling.2.3 Plasma membrane is the primary position of plant damage under the salt stress, that plant electrolyte leakage increased under salt stress was one of the important characters for salt damage; appropriate amount of exogenous substance all decreased the 1 electrolyte leakage in maize seedling under salt stress.2.4 T he capacity of active oxygen scavenging was increased, exogenous calcium （Ca）, phosphorus（P）, Potassium（K）, silicon（Si） and NO all increase the activity of SOD, CAT, POD in leaf and root at the different extent, at the same time, exogenous substance decreased the content of lipid peroxidation material-MDA.2.5 Exogenous substance accelerate transportation of osmotic adjustable substance in maize seedling under salt stress, osmotic adjustable substance can be distributed more reasonable in leaf and root, osmotic adjustment ability of maize was increased. It was lie on that whether the osmotic adjustable substance distributing in the leaf and root reasonable or not, when we estimated the magnitude of osmotic adjustment ability, and the magnitude of osmotic adjustable substance in the leaf could not completely explain the magnitude of osmotic adjustment ability. It may be an important aspect that exogenous substance improves the salt tolerance in maize seedling.2.6 Exogenous calcium（Ca）, phosphorus（P）, Potassium（K）, silicon（Si） and NO decrease the ratio of Na⁺/K⁺ and Na⁺/Ca²⁺, maintain the ion balance in different part of maize seedling under salt stress.These effects caused by exogenous calcium（Ca）, phosphorus（P）, Potassium（K）, silicon（Si） and NO on maize seedling under salt stress was the integrated result of improving ion absorption , distribution , growth and development in maize seedling. Whereas its mechanism of effect was diverse, but they all attach the aim which alleviative the salt damage, this illuminate that the direct mechanism of improving the salt tolerance through exogenous substance is not only.更多还原