不同pH、氮素形态和Ca～（2+）对玉米根形态发育及营养元素转运的影响

【作者】 杨丽琴；

【导师】 封克；

【作者基本信息】 扬州大学 ， 植物营养学， 2006， 硕士

【摘要】 本文通过对玉米营养液设定不同pH、氮素形态、外源钙浓度,并加入镉进行处理,观察了玉米根中钙离子分布和植株根系发育情况,测定了生物量积累、木质部营养元素转运量和镉的转运速率,结果表明:（1）pH 4.0处理的根细胞结构中Ca²⁺明显少于pH 6.0处理;低pH造成质壁分离;铵态氮处理的细胞结构中Ca²⁺明显少于硝态氮处理,尤其在细胞间质、细胞壁、细胞膜上的钙减少明显;铵态氮源处理也会导致细胞出现质壁分离,细胞结构松散,胞质外流,低pH会加重这些现象。当细胞壁和细胞膜上的Ca²⁺被铵离子取代后,细胞壁和细胞膜的结构遭到破坏,造成细胞壁结构松散,细胞膜破裂,从而引起胞质外流;（2）硝态氮促进玉米植株侧根的生长和生物量的积累;铵态氮处理促进了中柱的发育,木质部导管形成早,导管半径大,使植株根的平均直径要大于硝态氮处理;NH₄⁺的毒害可能是由于在较高的NH₄⁺浓度条件下,NH₄⁺将细胞膜上的Ca²⁺同时取代下来,破坏了细胞膜结构;增加外源钙的浓度,在一定程度上缓解了H⁺和NH₄⁺-N对玉米根发育的抑制作用;（3）铵态氮处理下植株木质部汁液中大量存在的NH₄⁺使玉米植株的生物量减少;NO₃^-吸收促进木质部汁液的pH升高;在植物吸收营养离子时,Ca²⁺和K⁺的互相协助主要体现在总量上;铵态氮处理的植株木质部中钙的转运速率明显低于硝态氮,NO₃^-促进钙的吸收;低pH,高铵,缺钙条件下植株木质部汁液及多种营养元素转运较低,可能是几种逆境导致植株根系活力降低,吸收水分和养分的能力下降的缘故;（4）pH 6.0处理下Cd的转运速率大于pH 4.0处理,pH降低时,由于H⁺与Cd²⁺竞争加剧,植物吸收镉的能力受到显著抑制;无论是硝态氮源还是铵态氮源,缺钙时玉米木质部汁液中Cd的转运速率均比供钙时小;供钙植株的镉转运量大可能更多还原

【Abstract】 Solution culture experiments were carried out to explore the effects of some environmental factors, medium pH levels, nitrogen forms, Ca concentration and Cd on the distribution of Ca²⁺ in maize roots, the development of roots, the biomass of seedlings and the transport of nutrition elements and Cd. The results indicated that:（1） There was less Ca²⁺ in root cells under pH4.0 than under pH6.0. Low pH caused plasmolysis. Nitrate treatment led to less Ca²⁺ in the cells of wheat roots than ammonium treatment, especially in intercellular substances, cell wall and membrane. In the presence of ammonium, plasmolysis, loose of cell structures and cytoplasma outflow could be observed, which might due to Ca²⁺ in cell wall and membrane was replaced by NH₄⁺ and the structures of cell wall and membrane were destroyed. Moreover, low pH level aggravated the negative influence.（2） NO₃^--N promoted the growth of lateral roots of maize and biomass of seedlings. NH₄⁺-N stimulated the development of vascular cylinder, where xylem vessels elements developed early and had large radius, which caused the roots of maize treated with NH₄⁺-N showed larger mean diameter than that treated with NO3―-N. The reason for NH₄⁺ toxicity may be that NH₄⁺ with high concentration took place of Ca²⁺ in cell membrane simultaneously and further damaged the structures of cell membrane. Increase of Ca²⁺ in outer medium could alleviate to some extent the inhibitory effects of low pH and NH₄⁺-N on the development of maize roots.（3） Too much NH₄⁺ in xylem sap reduced biomass of maize treated with NH₄⁺-N. Uptake of NO₃^- heightened pH value of xylem sap. Mutual facilitation of Ca²⁺ and K⁺ uptake mainly manifested in total quantities. Transport rate of Ca²⁺ in xylem sap of maize treated with NH₄⁺-N was higher than that treated NO3―-N, though NO3― promoted the absorption of Ca²⁺. Under the conditions of low pH, high concentration of NH₄⁺and lack of Ca, the transport of nutrition ions in xylem sap relatively decreased, maybe because these stresses cut down the vitality of roots,更多还原