【作者】 朱士农；

【导师】 郭世荣；

【作者基本信息】 南京农业大学 ， 设施园艺学， 2011， 博士

【摘要】 西瓜(Citrullus lanatus Mansfeld)是世界性的重要瓜类蔬菜,也是我国栽培面积最大、种植范围最广的主要瓜类蔬菜之一。近年来,土壤盐渍化严重影响了西瓜产量和品质,阻碍着西瓜设施栽培的可持续发展。因此,寻求克服土壤盐渍化的途径和方法已经迫在眉睫。实践证明,嫁接是克服土壤盐害的一项有效措施。本研究采用营养液栽培,以‘超丰抗生王’葫芦为砧木,‘秀丽’小型西瓜为接穗,探讨了100 mmol·L-1 NaCl胁迫下西瓜嫁接苗的生理响应及其耐盐性的生理机制,为嫁接技术在生产中的应用提供理论依据。主要结果如下：(1)采用营养液栽培,选用‘超丰抗生王’、‘将军’、‘丰源先锋’、‘南砧1号’、‘青砧1号’、‘瓠瓜苏清’为砧木,‘早春红玉’和‘秀丽’小型西瓜品种为接穗,首选筛选了西瓜嫁接优良砧木品种和嫁接砧穗组合。结果表明,盐胁迫下,南瓜砧木‘将军’、葫芦砧木‘超丰抗生王’优良株率分别达94%和92%,为较理想的西瓜嫁接砧木材料；‘超丰抗生王’/‘秀丽’、‘将军’/‘秀丽’组合的嫁接苗在盐胁迫下的成活率分别为93.6%和90.5%,为较理想的嫁接组合。因此,本研究选用了‘超丰抗生王’/‘秀丽’组合为研究对象。(2)盐胁迫下,西瓜嫁接苗的生物量显著提高,自根苗和嫁接苗叶片H2O2、MDA含量和质膜相对透性均显著增加,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性均显著升高,AsA和GSH含量显著降低；而嫁接苗叶片H2O2、MDA含量和质膜相对透性增加幅度以及AsA、GSH含量的降低幅度小于自根苗,抗氧化酶活性的增加幅度大于自根苗。说明嫁接可明显增强植株的活性氧清除能力,从而降低膜脂过氧化程度,提高西瓜幼苗的耐盐性。(3)盐胁迫下,自根苗叶绿素a (Chl a)、叶绿素b (Chl b)、总的叶绿素含量和Chl a/Chl b随时间的变化而显著下降。与自根苗相比,嫁接苗下降的幅度较小。盐胁迫下,自根苗叶片的净光合速率(Pn)、气孔导度(Gs)、胞间C02浓度(Ci)和蒸腾速率(Tr)均显著降低,而气孔限制值(Ls)升高,并在胁迫第8天达到极显著水平。与自根苗相比,嫁接显著降低盐胁迫下西瓜幼苗Ls,提高了Pn。上述结果表明,嫁接能够降低盐胁迫对西瓜幼苗光合作用的抑制,改善植株光合效率。(4)盐胁迫下,自根苗最大光化学效率(Fv/Fm)、光条件下最大光化学效率(Fv’/Fm’)、PSII实际光化学效率(ΦPSⅡ)、光化学淬灭系数(qP)、非光化学淬灭系数(qN)和PSⅡ相对电子传递速率(rETR)随时间变化显著下降,而嫁接苗中这些参数的下降幅度较小；叶绿体超微结构观察显示,盐胁迫下自根苗叶绿体膨胀,结构松散、紊乱以至解体,特别是基质片层断裂、消失,类囊体膜裂开,叶绿体内部脂质球出现数目增多,而嫁接苗间质和基粒片层清晰可见,类囊体膜仍保持完整。试验结果表明,嫁接有利于保护盐胁迫下西瓜幼苗光合膜结构的完整,保护西瓜植株叶片PSⅡ,增强PSⅡ在盐胁迫下的原初光能转化效率,可促进光合作用原初反应过程,进而促进光合作用。(5)西瓜嫁接苗地下部比地上部截留了较多的Na+,而地上部的K+含量明显高于地下部；嫁接苗对Na+的根部截流和K+的地上部吸收能力强于自根苗。西瓜嫁接苗可阻隔根系内皮层对Na+向中柱导管中的运输以及限制Na+向中柱导管中的装载,进而将Na+较多地截流在根部,阻止其向地上部分运输；同时将K+较多地运输到地上部分,使地上部保持较高的[K+]/[Na+]比值,从而保持西瓜嫁接苗较强的耐盐性。更多还原

【Abstract】 Watermelon (Citrullus lanatus Mansfeld) is the world’s major vegetable, and is also one of the principal fruit crops which has the largest planting area and is most widely cultivated in China. Impact of soil salinity has become a major factor that affects the yield and quality of watermelon, it is a serious impediment to the sustainable development of watermelon’s facility cultivation, and grafting is an important technology to overcome soil salt. In this paper, the influence of grafting to watermelon seedlings under salt stress and physiological responses is studied, furthermore, the physiological and biochemical mechanism through which grafting improves the salt tolerance ability of watermelon seedlings is explored, and the following results are achieved:(1) Using nutrient solution for culture, choosing ’super-abundance of antibiotic King’, ’General’,’Fengyuan Pioneer’,’South anvil 1’,’Green anvil 1’,’Gourd’ as rootstock,’the ruby in early spring’,’beauty’ as scion,we have studied the effect of the treatment of 200 mmol·L-1 NaCl on the salt tolerance ability of the rootstock and the affinity between the rootstock and the scion. The results showed that under salt stress, the excellent strain rates of pumpkin rootstock general, super abundance of antibiotic Wang were separately 94% and 92%, and they the ideal grafting stock material;The grafted seedlings of the combination of super-abundance of antibiotic King/beautiful, general/beautiful have the survival rates of 93.6% and 90.5% under salt stress, for the ideal grafting combination, which can be used for the grafting cultivation of facility watermelon.(2) Using nutrient solution for culture, choosing the ’super-abundance of antibiotic King’ gourd as rootstock,’beautiful’watermelon as the scion, we have studied the effect of a salt stress on the Antioxidant Systems of self-rooted and grafted watermelon. The results showed that under salt stress, the leaves’ H2O2, MDA content and membrane’s relative permeability of self-rooted and grafted watermelon was significantly increased, the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) was significantly increased, the content of AsA and GSH were significantly reduced;but the increasing extent of the leaves’ H2O2, MDA content and membrane’s relative permeability of grafted watermelon and the decreasing extent of AsA, GSH content were both less than self-rooted seedlings, and the increasing rate of antioxidant enzyme activity was more than self-rooted seedlings. It showed that grafting can significantly enhance plants’ ability of eliminating active oxygen, which can reduce the extent of lipid peroxidation, and increase the salt tolerance ability of watermelon seedlings.(3) Using watermelon seedlings as materials, we have studied the effect of grafting on watermelon seedlings chlorophyll (Ch) content and gas exchange parameters under NaCl stress. The results showed that:under NaCl stress, with treatment time prolonging, the decreasing extent of Ch a, Ch b, total Ch content, and ratio of Ch a/Ch b in grafted watermelon seedlings was less than that in self-rooted seedings. Under salt stress, Pn, Gs, Ci, and Tr of self-rooted and grafted seedlings were all significantly lower, but Ls was significantly increased, and all these indicators were to reach a very significant level at the eighth day. Compare with self-rooted seedlings, grafting could decrease the extent of Ls significantly, and increase Pn. These results showed that grafting could lighten the photosynthesis inhibition, and improve the photosynthetic rate of watermelon seedlings under salt stress.(4) Using watermelon seedlings as materials, we have studied the effect of grafting on watermelon seedlings chlorophyll fluorescence and the chloroplast ultrastructure under NaCl stress. The results showed that, under NaCl stress, with treatment time prolonging, the decreasing extent of Fv/Fm, Fv’/Fm’,ΦPSⅡ, qP, qN, and rETR in grafted watermelon seedings was less than that in self-rooted seedlings. Transmission electron microscopy observation indicated that, under NaCl stress, the chloroplast lamellae structure in self-rooted seedings presented loose, and stroma lamellae arranged disorderly, and plastoglobuli increased. Compare with self-rooted seedlings, the chloroplast lamellae structure in grafted watermelon seedings was better, and the photosynthetic membrane still kept completeness. The test showed that, under salt stress, grafting could play a significant role in protecting the photosynthetic membrane of watermelon, protect watermelon PSⅡ, enhance the primary light to energy conversion efficiency of its PSⅡand can promote the primary reaction process of photosynthesis, thus contributing to photosynthesis.(5) Using nutrient solution for culture, conducting NaCl salt stress treatment, and using the gourd rootstock which has stronger salt tolerance ability to graft watermelon,having studied the effect of grafting on the Na+, K+ content of graftet watermelon seedlings’root segment and overground segment, various parts of root tissues under salt stress. The results showed that the grafted watermelon seedlings intercepted more Na+ in underground part than in overground part, while the K+ content of overground part was significantly higher than that of the underground;the ability of grafted seedlings’root closure of Na+ and the above-ground absorbtion of K+ is stronger than self-rooted.Those explained that graftet watermelon seedlings can separate the transportation of Na+ from roots’inner cortex to the column tube and limit the loading of Na+ to the column tube, and then intercepted Na+ more in the roots and prevent it from transporting to the overground;while transporting K+ more to the overground part, maintaining a high [K+]/[Na+] ratio in the overground part, thereby maintaining a strong salt tolerance ability of grafted watermelon.更多还原