【作者】 高青海；

【导师】 王秀峰；

【作者基本信息】 山东农业大学 ， 蔬菜学， 2008， 博士

【摘要】 在设施生产中,由于自身的特殊环境及大量肥料施入,加之无雨水淋洗等原因,造成了设施土壤次生盐渍化,不仅严重影响了作物的生长,而且降低其产量及品质。黄瓜(Cucumis sativus L.)是我国设施栽培面积最大蔬菜作物之一,由于其根系较浅,具有喜肥不耐肥的特点,容易发生盐害。土壤次生盐渍化已成为设施黄瓜生产的主要障碍,其中主要的胁迫阴离子为NO3-。稀土镧在一定程度上可以提高植物的抗逆能力,缓解逆境胁迫。因此探讨LaCl3缓解黄瓜硝酸盐胁迫机理,对指导黄瓜可持续生产和提高我国园艺设施的利用率具有重要的理论和实践意义。本课题在已有研究的基础上,采用水培方法,设定不同浓度的LaCl3处理黄瓜种子及幼苗,探讨硝酸盐胁迫下,LaCl3对黄瓜种子萌发、幼苗碳氮代谢、保护酶活性、矿质元素吸收及亚细胞分布、内源激素变化等的影响,以期为减轻设施土壤次生盐渍化危害奠定理论基础及开辟新的途径。取得主要结果如下:1. LaCl3缓解硝酸盐胁迫下黄瓜种子萌发机理的研究采用两个黄瓜品种,100mmol·L -1硝酸盐胁迫,探讨不同浓度LaCl3对硝酸盐胁迫下黄瓜种子萌发生理特性的影响。研究结果表明,添加浓度为0.05mmol·L-1、0.1mmol·L-1、0.5mmol·L-1的LaCl3可以不同程度缓解盐胁迫对黄瓜种子萌发产生的影响,这主要表现在加入低浓度的LaCl3后提高了黄瓜幼芽中ɑ-淀粉酶、β-淀粉酶及脱氢酶活性,增加了可溶性蛋白的含量,进而促进侧根、胚根、胚轴的生长;而加高浓度LaCl3(1mmol·L-1)则抑制黄瓜种子的萌发。加低浓度LaCl3(小于0.5 mmol·L-1)降低膜脂过氧化产物MDA含量及相对电导率,增强了种子对盐渍环境的抵抗能力,缓解了盐害,但是浓度为1mmol·L-1的LaCl3不仅没有缓解硝酸盐对种子萌发产生的胁迫,反而抑制了种子的萌发,对其产生毒害作用。综合比较各项指标,加0.05mmol·L-1LaCl3缓解效果较好。2.硝酸盐胁迫下,LaCl3对黄瓜碳氮代谢的影响采用水培方法,研究不同浓度LaCl3对硝酸盐胁迫下黄瓜幼苗碳氮代谢的影响,硝酸盐胁迫浓度140mmol·L-1 NO3-, LaCl3浓度分别为0.05 mmol·L-1、0.5 mmol·L-1。结果发现,硝酸盐胁迫初期,黄瓜NR活性升高,但GS、GOGAT活性降低,硝酸盐含量增加;处理后期NR活性降低,引起黄瓜体内NH4+含量增加,因此抑制了黄瓜幼苗的生长,表现在抑制了黄瓜伸长生长、叶片面积的伸展,进而影响到生物量的积累,降低了植株鲜重。添加一定浓度的LaCl3可以提高黄瓜幼苗NR、GS、GOGAT活性,降低硝酸及铵态氮含量,有效缓解硝酸盐胁迫,氮代谢有所恢复,促进硝酸盐胁迫下黄瓜幼苗的生长。但是高浓度的LaCl3没有明显的缓解黄瓜硝酸盐胁迫的效果。硝酸盐胁迫下,黄瓜幼苗叶片及根系的蔗糖合成酶(SS)活性均降低,对黄瓜蔗糖磷酸合成酶(SPS)活性影响不大。与对照相比,在硝酸盐胁迫初期,黄瓜叶片及根系的可溶性糖、总糖的含量增加,但胁迫后期降低。加一定浓度的LaCl3可以提高黄瓜蔗糖合成酶的活性,提高胁迫下碳代谢水平。但是加高浓度的LaCl3效果不明显,反而与硝酸盐胁迫起到协同效应。3. LaCl3对硝酸盐胁迫下黄瓜光合特性的影响采用水培的方法,研究了LaCl3对硝酸盐胁迫下黄瓜幼苗光合特性的影响。结果表明硝酸盐胁迫明显抑制了黄瓜叶绿素及类胡萝卜素的含量,且随着处理时间的延长,其含量迅速降低;硝酸盐胁迫初期,光合速率的降低以气孔限制为主,叶片AQY与CE也下降,胁迫后期则以非气孔限制为主。外加LaCl3明显提高了硝酸盐胁迫下黄瓜叶绿素及类胡萝卜素的含量,而且LaCl3具有降低气孔的关闭,改善叶片的气体交换,提高叶片Fv/Fm、ФPSII、AQY、CE及qp等作用;提高了在胁迫下黄瓜幼苗对光能利用及CO2同化的能力。在胁迫处理初期,添加LaCl3均有提高盐胁迫下黄瓜幼苗光合作用的效果;但是在胁迫后期,高浓度(0.2mmol·L-1)LaCl3则降低了黄瓜的光合速率,而低浓度(0.02 mmol·L-1)LaCl3的恢复效果仍较明显。同时也发现,高温条件下LaCl3浓度越低,处理效果越明显,高温促进了黄瓜对LaCl3吸收。4. LaCl3对硝酸盐胁迫下黄瓜幼苗叶片抗氧化酶活性的影响采用水培方法,研究了LaCl3对硝酸盐胁迫黄瓜幼苗的生长及叶片抗氧化酶活性的影响。结果发现,硝酸盐胁迫显著抑制了黄瓜幼苗的生长,尤其是地上部生长。在处理7 d时,与对照相比,硝酸盐胁迫下的黄瓜单株地上部鲜重降低了12.77 g,叶片SOD、POD、CAT活性升高,而APX、DHAR和GR活性显著降低。外加低浓度(0.05 mmol·L-1)LaCl3不仅可以显著提高硝酸盐胁迫下黄瓜幼苗单株鲜重,叶片SOD、POD、CAT、APX、DHAR和GR活性及热稳定蛋白含量,而且还降低了黄瓜叶片电解质渗漏率及MDA含量,在一定程度上缓解了硝酸盐对黄瓜幼苗生长的抑制作用,比硝酸盐胁迫下黄瓜单株地上鲜重提高35%左右。但外加高浓度(0.5 mmol·L-1) LaCl3长期处理对黄瓜硝酸盐胁迫的缓解效果并不明显。5. LaCl3对硝酸盐胁迫下黄瓜幼苗矿质元素吸收、分布及膜蛋白酶活性的影响采用水培的方法,研究了LaCl3对硝酸盐胁迫下黄瓜幼苗矿质元素的亚细胞分布及膜蛋白酶活性的影响,探讨LaCl3在硝酸盐胁迫中的缓解作用。结果表明,硝酸盐胁迫下,黄瓜叶片及根系中Ca、K含量增加,Fe、Mg含量降低。加一定浓度的LaCl3处理明显降低了叶片及根系中Ca、K含量,提高了黄瓜叶片Fe、Mg含量。硝酸盐胁迫也影响了Ca、K等在黄瓜亚细胞分布,特别是细胞质中的Ca、K含量显著增加,叶绿体等细胞器中的Fe、Mg含量显著降低。低浓度的LaCl3处理明显改善了Ca、K在黄瓜亚细胞中的分布,降低了Ca、K在细胞质中的含量,提高Fe、Mg在叶绿体等细胞器中的含量。LaCl3影响黄瓜吸收的矿质元素在亚细胞中分布,主要是通过提高黄瓜叶片及根系质膜、液胞膜H+-ATP, H+- PPase (焦磷酸),Ca2+-ATPase活性,促进离子的运输,对P在体内进行了有效分配。但加高浓度的LaCl3处理,尽管也可以降低黄瓜对Ca、K吸收,但大量La3+本身也会对黄瓜幼苗产生毒害。6. LaCl3硝酸盐胁迫下对黄瓜内源激素变化的影响硝酸盐胁迫下黄瓜叶片中的内源激素含量低于根系。与对照相比,硝酸盐胁迫使黄瓜叶片及根系中生长素类和细胞分裂素类含量均降低,ABA含量升高。加一定浓度的LaCl3可以促进细胞分裂素的合成及向地上部运输,提高叶片细胞分裂素的含量,维持黄瓜幼苗较高的内源激素水平,有助于缓解黄瓜幼苗硝酸盐胁迫。但高浓度LaCl3处理的缓解效果并不明显。更多还原

【Abstract】 Special environment, intensive fertilizer input, and no rainwater leaching and other cause during protected cultivation, often led to soil salinization. Soil salinization not only seriously influenced plant growth, but also decreased yield and quality. Cucumber (Cucumis sativus L.) is widely planted in greenhouse. Cucumber roots are shallowly distributed and show preference for fertilizer, but no tolerance to excess fertilizer, so cucumber can be easily affected by salinization. Soil salinization has been a main barrier of protected cucumber production. Lanthanum can to a certain degree improve the resistance of plants to envirvnmental stresses.Therefore, study on mechanism of LaCl3 nelieving nitrate stress has the important theoretical and practical meaning to guide sustainable production and increase utilization efficiency of protected cultivation.In this study, hydroponic culture experiments were conducted to investigate the effects of LaCl3 on seed germination, carbon and nitrogen metabolism, protective enzyme activity, mineral elements uptake and subcellular distribution and the changes of endogenous hormones. The objective of this paper is to lay theoretical formelation and propse new measures for alleviation of salinity injury. The main results were presented as follows:1. Research on effects of lanthanum alleviating nitrate stress on cucumber seeds germinationSeeds of two cucumber varities were used to study the effects of different LaCl3 concentrations on seeds germinabality and the physiological and biochemical properties during the germination under nitrate stress.The results showed that 0.05 mmol·L-1, 0.1 mmol·L-1 and 0.5 mmol·L-1 LaCl3 could, to different degress alleviate salt stress, low concentration LaCl3 could enhanceα-amylase,β-amylase,dehydrogenase activity and increase the content of soluble protein, thereby promoting the growth of branch roots, radicel and axis; but high concentration(1mmol·L-1) LaCl3 inhibited the germination of seeds.Low concentration LaCl3 (less than 0.5 mmol·L-1) alleviated the nitrate injury and improved resistance of seeds to nitrate stress by reducing the content of MDA and relative electrolytic leakage. But high concentration (1mmol·L-1) LaCl3, which inhibited the germination of seeds, was deleterious to the seeds and thus failed to alleviate the cucumber seeds germination under nitrate stress. Compared all indexes comprehensively, we found that 0.05 mmol·L-1 LaCl3 was the best concentration in alleviating the cucumber seeds germination under nitrate stress.2. Effects LaCl3 on carbon and nitrogen metabolism under nitrate stress in cucumber seedlingsIn this experiment, cucumber seedlings were treated which high concentration nitrate (140mmol·L-1NO3-) and LaCl3. The results showed that NR activity in leaves increased at early stage of stress, but GS and GOGAT activties decreased;NR activty decreased at later stage of stress, compared to the control. Nitrate and NH4+ contents increased in cucumber seedlings under nitrate stress, which inhibited growth of cucumber seedlings. As a result, such as plant height, leaf area and biomass accumulation were reduced. Exogenous LaCl3 could improve NR、GS and GOGAT activtives in cucumber seedlings and reduceud nitrate and NH4+ contents, which could alleviate the reduce of nitrogen metabolism and promote cucumber seedling growth. Excess nitrate significantly reduced SS activity in cucumber seedlings, but had obvious effect on SPS. Souble sugar and total sugar contents of cucumber increased at eafly stage of stage, but reduced at later stage. Low LaCl3 could improve SS activity of ccucumber seedlings and promote carbon metabolism, but high LaCl3 brought combined effects to cucumber seedolings under nitrate stress.3. Effects of LaCl3 on photosynthetical characteristics in cucumber seedlings under nitrate stressThe effects of LaCl3 on photosynthetical characteristics of hydroponically cultivated cucumber seedlings were investigated under nitrate stress, and we discussed the mechanism of LaCl3 alleviating nitrate stress. The results showed that chorophyll content and carotenoids contents of cucumber seedlings were significantly restrained by nitrate stress, and quickly decreased with prolength of treatment ; Decreased photosynthetic rate due to stomatal limitation during the early nitrate stress period, but was non-stomatal limitation at later stage of stress. Exogenous LaCl3 could enhance chorophyll content of cucumber seedlings under nitrate stress and improve the gas exchange. Fv/Fm,ФPSII, AQY, CE and qp in cucumber seedlings under nitrate stress increased by applying LaCl3 , resulting in increased cucumber light utilization efficiency and CO2 assimilation. When dealing with it ,in addition,it could accelerate the effect of photosynthesis , but the effect of 0.02 mmol·L-1 LaCl3 also significanted, 0.2 mmol·L-1 LaCl3 reduced the photosynthetic rate of cucumber at threatening anaphase. Addition of different concentration LaCl3 could improve photosynthesis at primary stage of nitrate stress; but high LaCl3 (0.2 mmol·L-1) decreased photosynthesis, while low LaCl3 (0.02 mmol·L-1) also could still maintain high photosynthesis at later stage of stress.4. Effects of LaCl3 on antioxidant enzymes activities in cucumber leaves under nitrate stressEffects of LaCl3 on plant growth and antioxidant enzymes in cucumber leaves under nitrate stress were studied by hydroponics. The results indicated that the growth of cucumber roots and shoots was significantly inhibited by nitrate stress, especially the shoot. The shoot fresh weight per plant reduced 12.77 g , activities of SOD, POD and CAT increased, but APX、DHAR and GR activities significantly reduced compared to control. Application of LaCl3 markedly increased fresh weight , thermally stable protein content of leaves, activities of SOD, POD, CAT, APX, DHAR and GR, and resulted in decreased MDA content and electrolytic leakage of cucumber leaves under nitrate stress. After 7 days of treatment, addition of 0.05 mmol·L-1LaCl3 alleviated inhibition of cucumber growth by nitrate stress to some extent, shoot fresh weight increased by 35%; Application of high concentration LaCl3 had no alleviated obvious effect. So, we concluded that addition of certain concentration LaCl3 could alleviate nitrate stress on cucumber by increasing activities of antioxidative enzymes and content of thermally stable protein.5. Effects of LaCl3 on absorption and subcelluar distribution of the mineral elements in cucumber leaves under nitrate stressEffects of LaCl3 on absorption and subcelluar distribution of the mineral elements in cucumber leaves under nitrate stress were studied by hydroponics. Ca and K content of cucumber seedlings increased Fe and Mg content reduced compared to control. Application of low LaCl3 treatment considerably reduced the Ca、K content and increased Fe、Mg conten.High nitrate had effectes on subcelluar distribution of Ca、K and Fe、Mg in cucumber seedlings, especially increased Ca、K content of cytoplasm and reduced Fe、Mg content of chloroplast. Low LaCl3 significantly improved cytoplasm distribution of Ca、K and increased Fe、Mg content of chloroplast. LaCl3 treatment could improve activity of H+-ATP, Ca2+-ATPase and H+- ppase in the plasma and vacuole membrane of cucumber seedlings, and promote ion transportation and P absorption, which were causes of the effects of LaCl3 on subcelluar distribution of the mineral elements. LaCl3 of high concentration could reduce absorption of Ca、K, but La3+ could enter cytoplasm, causing injury on cucumber seedlings.6. Effects of LaCl3 on changes of endogenous hormones in cucumber leaves under nitrate stressEndogenous hormones of root were higher than those of leaf in cucumber seedlings under nitrate stress, the content of auxin and cytokinin reduced, but ABA content increased in cucumber, compared to control. Application of LaCl3 could promote cytokinin synthesis and shoot transportation, so increased cytokinin content of shoot, thereby maintaining higher level of endogenous hormones, which was helpful in alleviating nitrate stress, however, LaCl3 of high concentration had no allevating effects.更多还原