【作者】 薛忠财；

【导师】 高辉远；

【作者基本信息】 山东农业大学 ， 生态学， 2011， 硕士

【摘要】 盐胁迫是影响植物生长的重要因素之一,因此阐明植物的抗盐机制对于选育抗盐品种和改良作物品质具有重要意义。本实验以抗盐性较强的东营野生大豆(Glycine soja Sieb. et Zucc. ZYD 03262)和广泛栽培的山东栽培大豆(Glycine max (L.) Merr.山宁11号)为实验材料,研究了两种大豆对不同浓度NaCl(0,100,200mM)处理的响应,从光合作用、光能利用效率、抗氧化酶活性、离子分布等角度,探讨了东营野生大豆的耐盐机理,为利用野生大豆资源提高栽培大豆抗盐能力提供理论依据。结果表明:经过不同浓度NaCl处理15天后,两种大豆植株生长均受到抑制,叶片的叶绿素含量(Chl a~+b),相对含水量(RWC),光合速率(Pn),实际光化学效率(ΦPSII)都明显降低,然而NaCl处理对栽培大豆的抑制作用显著大于野生大豆;野生大豆叶片中的Na~+含量、Na~+/K~+值都显著低于栽培大豆,但野生大豆根中的Na~+含量却明显高于栽培大豆。虽然野生大豆在NaCl处理下能够维持较高的光合能力,但是野生大豆所具有的这种抗盐能力是由于叶片光合机构本身具有较强的抗盐性,还是由于植株的根、茎部具有较强的离子选择性有关。因此为了排除根和茎中相关机制的影响,我们用不同浓度的NaCl溶液直接处理两种大豆离体叶片。结果表明当用100和200mM NaCl溶液处理两种大豆的离体叶片时,野生大豆的PSII最大光化学效率(Fv/Fm)、ΦPSII、单位面积有活性反应中心的数目(RC/CSo)和光化学性能指数(PI)下降幅度却显著大于栽培大豆;同时,野生大豆叶片中的Na~+含量也显著高于栽培大豆。通过分析NaCl处理后野生大豆和栽培大豆叶片的光合能力(Pn、Fv/Fm、ΦPSII)与叶片中Na~+含量的关系,我们可以看出无论是植株还是离体叶片,叶片中Na~+的含量对野生大豆伤害要显著大于对栽培大豆的伤害。非损伤微测技术(NMT)的测定结果表明,经过NaCl处理后,栽培大豆根部具有比野生大豆更明显的Na~+外排现象,但是野生大豆叶片中Na~+的外排更为显著。另外,抗氧化酶活性的分析表明,野生大豆叶片中的超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)和过氧化氢酶(CAT)活性在经过不同浓度NaCl处理后显著增加,而栽培大豆在经过NaCl处理后叶片中SOD的活性增加,APX、CAT活性下降。与栽培大豆相比,野生大豆在根部积累了更多的Na~+,同时能够选择性地吸收更多K~+,有利于维持细胞的渗透势,保持植株对水分的吸收,有效缓解了渗透胁迫对植株生长的影响。另外,野生大豆可以通过提高抗氧化酶活性有效地消除过量的活性氧,避免了活性氧对光系统和光合碳同化过程中多种酶的伤害,为保护光合机构,维持较高的光合能力提供了条件。野生大豆叶片光合机构并不比栽培大豆更抗盐,但是由于野生大豆利用相关的选择和转运机制有效地降低了叶片中Na~+含量,保护叶片的光合机构免受Na~+的伤害,维持较高的光合能力,保证其在盐渍条件下的正常生长,这是野生大豆抗盐的一种主要机制。更多还原

【Abstract】 Salt stress is one of the major stress factors limiting growth of plant, so understanding the salt resistance mechanism of plant is very important to develop cultivars with increased salt tolerance. In this study, a wild soybean (Glycine soja Sieb. et Zucc. ZYD 03262) and a cultivated soybean (Glycine max (L.) Merr. Shanning 11) plants and their detached leaves were used as materials to study responses of their photosynthetic appratus to treatments with different NaCl concentrations (0, 100, 200mM). By comparing analyzsis of photosynthesis, photochemical efficiency, ion concentration and distribution, antioxidant enzymes activities between the two soybena plants, we explored the salt resistance mechanism of the wild soybean.The results showed that NaCl stress inhibited growth, photosynthesis (Pn), and decreased actual photochemical efficiency of PSII (ΦPSII), chlorophyll content (Chl a~+b) and relative water content (RWC) in the leaves of the two soybean plants, but the inhibition was more severe in cultivated soybean. The Na~+ concentrations and the ratio of Na~+/K~+ in leaves of the wild soybean were significantly lower than that of the cultivated soybean, while the Na~+ concentrations in roots of the wild soybean were higher than that of the cultivated soybean. However, according to the above results, it is impossible to clarify whether the photosynthetic apparatus in the wild soybean is more salt tolerant than that in the cultivated soybean because the selective absorption of Na~+ and K~+ through the roots and the translocation of Na~+ and K~+ through the stems can effectively decrease the Na~+ concentrations in the leaves, avoiding the Na~+-induced damage to the photosynthetic apparatus. To elucidate whether the photosynthetic apparatus of the wild soybean is more tolerant to salt stress, detached fully expanded leaves were directly subjected to NaCl treatments, which eliminated the effects of the roots and stems on the photosynthetic apparatuses in the leaves. When the detached leaves of the both soybeans were treated with 100 and 200mM NaCl, the maximal photochemical efficiency of PSII (Fv/Fm),ΦPSII, active PSII reaction centers per excited cross section (RC/CSo) and photosynthetic performance index (PI) decreased more significantly in the wild soybean than that in the cultivated soybean. Meanwhile the Na~+ concentrations in the detached leaves of the wild soybean were higher than that of the cultivated soybean when treated with 100 and 200mM NaCl. The correlations between the Na~+ concentrations and photosynthetic activities demonstrated that increasing Na~+ concentrations in leaves, regardless of whether attached or detached leaves, causes a more pronounced decrease in photosynthetic activities in wild soybean compared to cultivated soybean, that’s mean the Na~+ concentrations in leaves are mainly responsible for determining salt resistance in the two soybean species. According to the Non-invasive Micro-test Technique (NMT) data, the Na~+ effluxes in leaves of the wild soybean were significantly greater than those in leaves of the cultivated soybean; however, the Na~+ effluxes were more remarkably higher in roots of the cultivated soybean than in the wild soybean. The activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) in leaves of the wild soybean were increased, while the activities of APX and CAT were decreased and the activity of SOD increased in leaves of the cultivated soybean after treated with NaCl.In conclusion, the wild soybean is able to maintain normal water absorption via osmo-adjustments by accumulating higher levels of Na~+ and by absorbing more K~+ in its roots to avoid the osmotic stress caused by NaCl stress. The enhanced of activity of antioxidant enzymes can effectively eliminate the reactive oxygen species (ROS) to alleviate damage to photosystems and enzymes involved in CO2 assimilation, protecting photosynthetic apparatus against salt stress. Our results suggest that the photosynthetic apparatus in the wild soybean doesn’t have higher salt resistance than that in the cultivated soybean. However, the wild soybean prevents the accumulation of higher concentrations of Na~+ in leaves by certain mechanism, which protects its photosynthetic apparatus from salt damage, helping it to survive in saline soil.更多还原