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选择高感“大白菜芝麻状斑点病”品系03B9大白菜为试材,调查不同形态氮素营养对其发病的影响;并选择高抗品系C24、P8-1和高感品系03B9、P8-2为试材,在总氮素浓度为25mmol.L-1,NO3--N︰NH4+-N分别为3︰7、5︰5和7︰3的水培条件下,研究氮代谢和抗氧化系统生理指标的变化。结果表明:铵态氮促进芝麻状斑点病发生的作用高于硝态氮和酰胺态氮。随铵态氮比例的增大,感病品系03B9和P8-2较抗病品系病斑数显著增多,叶柄中PPO活性和铵态氮、MDA含量及电导率升高,NR活性和多酚含量降低;抗病品系C24和P8-1叶柄中GDH活性和多酚含量升高,PPO活性、MDA含量及电导率变化不明显。推测营养液中铵态氮的比例增加,影响感病品系氮素代谢中有关酶类的活性,使体内铵态氮过量积累,导致细胞膜系统受到伤害,使液泡内的酚类物质与细胞质中的多酚氧化酶接触,引起褐变,在叶柄表面表现出芝麻斑点症状。
Select high sense “Chinese cabbage sesame speckle ” strain 03B9 Chinese cabbage as test material to investigate the impact of different forms of nitrogen nutrition on its incidence; and select high resistant lines C24, P8-1 and susceptible lines 03B9, P8 -2 was used as test material to study the effect of nitrogen metabolism and anti-nitrogen on the condition of total nitrogen concentration of 25mmol.L-1 and NO3 - N: NH4 + -N of 3︰7, 5︰5 and 7︰3 respectively. Changes in physiological indicators of oxidation system. The results showed that ammonium nitrogen promoted the occurrence of sesame speckle disease more than nitrate nitrogen and amido nitrogen. With the increase of the proportion of ammonium nitrogen, the susceptible lines 03B9 and P8-2 had significantly more lesions than the resistant lines, PPO activity, ammonium nitrogen content, MDA content and conductivity in petiole, NR activity and polyphenol content Decreased; the activities of GDH and polyphenol in the petioles of resistant lines C24 and P8-1 were increased, and the changes of PPO activity, MDA content and conductivity were not obvious. It is speculated that the proportion of ammonium nitrogen in nutrient solution increases, affecting the activity of enzymes involved in nitrogen metabolism in susceptible strains, causing excessive accumulation of ammonium nitrogen in the inoculum, resulting in damage to the cell membrane system, making phenols in vacuoles and cytoplasm Polyphenol oxidase contact, causing browning, showed sesame spots on the surface of petiole symptoms.