【作者】 弓瑞娟；

【导师】 张广华； 高洪波；

【作者基本信息】 河北农业大学 ， 园艺产品质量与安全， 2012， 硕士

【摘要】 近年来随着设施蔬菜面积日益扩大,过量施用化肥造成的后果日益严重,已成为蔬菜三大污染源之一,严重影响作物的产量和品质,并且通过食物链最终影响人类健康。叶菜类蔬菜最易富集硝酸盐,生菜(Lactuca sativa L.)作为设施广泛栽培的叶菜类蔬菜之一,在设施生产中生菜产量和品质的提高与施肥的关系非常密切,因此降低生菜体内硝酸盐含量对提高品质具有重要意义。γ-氨基丁酸(GABA)是一种四碳非蛋白质氨基酸,近年来有关外源GABA对植物生理代谢的研究主要集中于提高植物的抗逆性,但外源GABA对蔬菜品质影响的研究报道很少。为此,本试验以生菜为试材,采用水培法研究了外源GABA对植株生长和营养品质的影响,明确了外源添加GABA的最适浓度、最适方法、最适时间,并进一步研究了高氮胁迫下GABA影响生菜体内硝酸盐积累的内在机理和营养品质,以探讨生菜氮代谢的内在机理,为寻求降低叶菜类蔬菜硝酸盐含量、提高营养品质的有效措施提供理论依据。主要结果如下:(1)采用浸种、叶面喷施、营养液添加3种方法,研究了不同浓度GABA对植株生长和营养品质的影响。结果表明:3种施用GABA的方法均可促进生菜的生长,通过提高NR活性降低了体内硝酸盐含量,提高了生菜品质;但不同施用方法均存在浓度效应,其中浸种处理、叶面喷施、营养液添加GABA的浓度分别以5.00 mmol/L、100 mmol/L、2.50 mmol/L效果较好,在最适宜浓度下对生长和品质指标综合分析认为,营养液添加2.50 mmol/L GABA处理的效果最好。(2)营养液添加2.50 mmol/L GABA培养3-12 d的生菜生长量和营养品质均有所提高,但是在采收前6 d施用GABA时生菜地上部鲜重、硝酸还原酶(NR)活性以及氨基酸、蛋白质含量最高,而硝酸盐含量最低,其次为采收前9 d、12 d施用GABA,采收前3 d施用GABA效果最差。结果表明营养液外源添加GABA可提高生菜产量和品质,但存在时间效应,以采收前6 d施用GABA效果最佳。(3)采用营养液水培法,研究了高氮胁迫下(32 mmol/L)外源GABA对生菜生长和氮代谢及矿质元素含量的影响。结果表明:高氮胁迫下外源添加GABA显著促进生菜的生长,NR、亚硝酸还原酶(NiR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)活性显著提高,亚硝态氮(NO2--N)、铵态氮(NH4+-N)、α-酮戊二酸、氨基酸、可溶性蛋白、总氮含量显著增加,同时K+、Ca2+、Mg2+含量显著升高,根系活力明显提高,而硝态氮(NO3--N)、Mn、Fe含量大幅下降,谷氨酸脱氢酶(GDH)、谷氨酸脱羧酶(GAD)活性显著下降,缓解了高氮胁迫对生长的抑制;而高氮胁迫下同时添加GABA和钼酸钠处理进一步提高了GABA对高氮胁迫的缓解作用,而同时添加GABA和钨酸钠则降低了GABA对高氮胁迫的缓解作用,说明高氮胁迫下添加外源GABA可以通过诱导NR活性的提高促进硝酸盐的吸收和转化,从而缓解高氮胁迫对生菜的伤害。更多还原

【Abstract】 In recent years, with the development of facility vegetables growing,serious consequence caused by excessive application of fertilizer, has become one of the three major sources of vegetables pollution, seriously affect on crop yield and quality, and eventually affect human health by the food chain.Lettuce widely cultivated as one of the facilities leafy vegetables,the apply fertilizer has a very close relationship with improvement of the production yield and quality of lettuce.Thus reducing the content of lettuce nitrate has important meaning in improving the yield and quality.γ-aminobutyric acid (GABA) is a four-carbon non-protein amino acid conserved from bacteria to plants and vertebrates. In recent years,research about the exogenous GABA on metabolism of plant physiology mainly focused on theimprovement of resistance of salt stress , cold stress , hypoxia stress,but few reports about exogenous GABA on the effect of the quality in vegetables.So, a hydroponics experiment investigated that the effect of exogenous GABA on nitrogen metabolism and mineral elements contents of lettuce under different nitrogen level, defined the optimum time,concentration and method for add exogenous GABA,trial to further research to investigate the effect of exogenous GABA on the nitrogen metabolism and mineral elements contents under high nitrogen stress in hydroponics culture, In order to investigate the inner mechanism of the nitrogen metabolism,provide a theoretical basis for seeking a method to reduce the nitrate content of leafy vegetables , and effective measures to improve the quality.The paper investigated that the effect of different concentration GABA on growth and quality in lettuce using three different appliction method including soaking, leaf spraying and application GABA in nutrient solution under hydroponics of non-heading lettuce variety‘Dasu’. The results showed that three application method were all promoted the growth of lettuce, decreased the nitrate content and improved the quality through increasing nitrate reductase activity.But there existed the concentration effect under different application methods, among them, the preferable concentration of soaking, leaf spraying and application GABA in nutrient solution were 5.00 mmol/L, 100 mmol/L, 2.50 mmol/L respectively.The result showed that the effect of exogenous application 2.50 mmol/LGABA in nutrient solution was best both in growth and quality improvementA hydroponics experiment was conducted to investigate the effect of exogenous application GABA time on nitrate content and quality improvement in non-heading lettuce variety‘Dasu’. The results showed that the growth and quality of lettuce were all increased under the nutrient solution applying GABA 3-12 d. And the fresh weight, activity of nitrate reductase and contents of amino acid and protein were all highest, but the the nitrate content in leaves were the lowest. While the effects of treatment 9 d and 12 d were lower than that of 6 d, and the effect of 3 d was the lowest. The results indicated that application exogenous GABA could increased yield and quality of lettuce, but there existed time effects, and the effect of 6 d was best.The lettuce variety‘Dasu’was used to investigate the effect of exogenous GABA on the growth index,nitrogen metabolism and mineral elements contents under high nitrogen stress in hydroponics culture.The results showed that compared with high nitrogen stress,the activities of nitrate reductase (NR), nitrite reductase (NiR) and the contents of nitrite (NO2--N), ammonium (NH4+-N), amino acids, soluble protein,total nitrogen as well as K+, Ca2+, Mg2+ significantly increased,however the contents of nitrate (NO3--N),Mn, Fe obviously decreased, when lettuces were grown in the nutrient solution of GABA under high nitrogen stress.However, exogenous GABA and sodium molybdate application anesis the harm of high nitrogen stress to lettuce,while exogenous GABA and sodium tungstate application had opposite effects.The result indicated that exogenous GABA might alleviate the damage of lettuce from high nitrogen stress via enhanced NR activity and improving nitrate absorption and transformation, meanwhile increased K+, Ca2+, Mg2+contents and decreased Mn, Fe contents.更多还原