磁场对镉胁迫下绿豆幼苗生长的影响及其机理研究

【作者】 李冉；

【导师】 贺军民；

【作者基本信息】 陕西师范大学 ， 植物学， 2010， 硕士

【摘要】 生物磁学是研究和应用物质的磁性和磁场与生物特性之间相互联系和相互影响的一门新兴边缘学科。大量研究表明磁场处理能调动植物自身的调节作用,激发其内部活力,改善植物体内部的生理生化代谢,并对逆境胁迫如干旱、盐胁迫、低温等也有一定的缓解作用。镉(Cd2+)胁迫作为重金属胁迫的一种,会对植物产生伤害效应,影响植物的生长发育以及产量和品质。目前有关磁场对重金属抑制植物生长发育的影响及机理研究甚少。本研究以农作物绿豆幼苗为材料,通过外加磁场预处理,初步探讨了5μmol/LCd2+胁迫下磁场处理对绿豆幼苗生长发育的影响。并从膜脂过氧化、光合作用两方面入手,对其影响机理进行了分析,以期为提高植物抗重金属胁迫能力提供一定的理论基础。主要研究结果如下：0.与对照相比,0.6T磁场处理能促进绿豆幼苗株高和主根生长,使幼苗地上部分和根系的鲜、干重增加；相反,Cd2+胁迫下绿豆幼苗的株高和主根长受到抑制,地上部和根系的鲜、干重降低；而与单纯Cd2+胁迫相比,磁场与Cd2+复合处理不仅使幼苗株高增加,而且使主根长、地上部和根系的鲜、干重均增加。说明磁场预处理不仅促进了正常生长条件下绿豆幼苗的生长,而且促进了Cd2+胁迫下绿豆幼苗的生长。2.绿豆幼苗在Cd2+胁迫下叶片和根系的SOD、CAT、POD等保护酶活性在升高的同时,活性氧H2O2含量也增高,膜脂过氧化程度也加剧,表现在膜脂过氧化产物MDA含量明显增高；磁场预处理使绿豆幼苗叶片和根系的POD活性没有受到明显影响,但SOD和CAT活性均有一定程度的提高,使活性氧H2O2水平和膜脂过氧化产物MDA含量均降低；磁场与Cd2+复合处理与Cd2+单独处理相比,进一步提高了幼苗叶片和根系的SOD、CAT、POD等保护酶的活性,降低了幼苗叶片和根系的H2O2含量和膜脂过氧化产物MDA含量。说明磁场能通过诱导幼苗叶片和根系膜保护酶活性提高,使幼苗活性氧水平降低,进而降低了幼苗在正常生长条下及Cd2+胁迫下的膜脂过氧化程度。这可能是磁场促进正常生长条件下幼苗生长、显著缓解Cd2+胁迫抑制绿豆幼苗生长的原因之一。3.与对照相比,磁场处理使绿豆幼苗净光合速率、气孔导度、胞间隙CO2浓度明显升高,而气孔限制值无明显变化,说明磁场提高幼苗净光合速率的主要原因是气孔因素；而Cd2+胁迫降低了绿豆幼苗叶片的净光合速率、气孔导度、蒸腾速率、但胞间隙CO2浓度明显升高,而气孔限制值无明显变化,说明Cd2+抑制幼苗净光合速率的主要原因是非气孔因素；磁场预处理提高了Cd2+胁迫下绿豆幼苗叶片的净光合速率、气孔导度、蒸腾速率,而胞间隙CO2浓度明显降低、气孔限制值无显著变化,说明磁场处理提高了Cd2+胁迫下绿豆幼苗叶片叶肉细胞的光合能力,进而缓解Cd2+胁迫对绿豆幼苗叶片光合作用的抑制。上述结果也进一步说明磁场预处理促进正常生长条件下和Cd2+胁迫下绿豆幼苗生长的另一个原因是其促进了两种生长条件下幼苗的光合作用。磁场促进两种条件下幼苗光合作用的原因不仅有气孔因素,也有非气孔因素,但磁场促进正常生长条件下幼苗光合速率以气孔因素为主,而促进Cd2+胁迫幼苗光合速率以非气孔因素为主。更多还原

【Abstract】 Biomagnetism is new and interdisciplinary subject, it study magnetism of matter and the connection and affection between magnetic field and organisms. A lot of researches show magnetic field treatment can mobilize the regulation ability of plant, stimulate its vigour, improve metabolism physiologically. It can also alleviate the inhibited effect of adversity stress, such as drought, salt stress, low temperature. Cadmium (Cd2+) stress as one of the heavy metal stress could harm plants, affect their development and yield and quality. Now, information is still lacking regarding the effects and mechanisms of magnetic field on the growth of plant under heavy metal stress. We investigated the effects of magnetic field on the growth of plant under Cd2+ stress. In order to understand the mechanisms of magnetic field on the growth of plant under Cd2+ stress, we investigated effects of magnetic field on the membrane lipid peroxidation and photosynthesis of mung bean seedings under Cd2+ stress. The main results were presented as follows:1. Compared to control treatment,0.6T magnetic field treatment could raise mung bean seeding height and main root length, and the fresh and dry weight of the over-ground part and roots were also increased. By the contrast, when the mung bean seedings were under Cd2+ stress, growth of mung bean seedings was inhibited, and the fresh and dry weight of the over-ground part and roots were also decreased. However, we found the above inhibited effect of Cd2+ stress could be clearly alleviated by 0.6T magnetic field treatment. The results indicated that magnetic field treatment can not only improve the growth of mung bean seedings under normal circumstance but also alleviate the inhibited effect of Cd2+ stress on growth of mung bean seedings.2. Compared to control treatment, Cd2+ stress respectively increased the activities of SOD, CAT and POD in leaf and root of mung bean seedings, and at the same time raised the content of H2O2. Membrane lipid peroxidation was intensified, which was represented by the increase of MDA.0.6T magnetic field treatment did not influence the activities of POD in leaf and root of mung bean seedings, but the activities of SOD, CAT were increased to some extent, and caused a decrease of MDA content and H2O2 level in leaf and root of mung bean seedings. Compared to Cd2+ stress alone, treatment of MF+Cd2+ caused a decrease of MDA content and H2O2 level, and at the same time, more increases in SOD, CAT, POD activities in leaf and root of mung bean seedings. The results showed that magnetic field treatment might decrease the levels of reactive oxygen species, and then inhibit membrane lipid peroxidation in leaf and root of seedings under normal circumstance and Cd2+ stress by enhancing the activities of the three antioxidant enzymes, which may be one of the mechanisms that magnetic field treatment improved the growth of mung bean seedings under normal circumstance and alleviated the inhibited effect of Cd2+ stress on growth of mung bean seedings.3 Compared to control treatment,0.6T magnetic field treatment enhanced net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate respectively, but stomatal limitation was not changed by the magnetic field. These results showed that the magnetic field treatment-induced improvement of photosynthesis in mung bean seedings was mainly caused by stomatal factor. However, Cd2+ stress caused the decreases of net photosynthetic rate, stomatal conductance, transpiration rate, while intercellular CO2 concentration was enhanced and stomatal limitation was not changed respectively, showing that the inhibitive effect of Cd2+ stress on photosynthesis of mung bean seedings was mainly caused by nonstomatal factors.0.6T magnetic field treatment also enhanced net photosynthetic rate, stomatal conductance and transpiration rate, but reduced intercellular CO2 concentration and did not change stomatal limitation of mung bean seedings under Cd2+ stress respectively, which indicated that the magnetic field treatment enhanced the ability of photosynthesis of mung bean seedings under Cd2+ stress, so as to alleviate Cd2+ stress-induced inhibitive effect on photosynthesis in mung bean seedings. The above results further indicated that the other reason of promoting the growth of mung bean seedings by magnetic field treatment under normal condition and Cd2+ stress is the enhancement of photosynthesis of seedings by the magnetic field. Although under the two conditions, the magnetic field-induced improvement of photosynthesis in mung bean seedings was the results of both stomatal and nonstomatal factors, the stomatal limitation is dominant under normal condition, and the nonstomatal limitation becomes the dominant one under Cd2+ stress.更多还原