Effect of ratio of ammonium to nitrate on organic acid and starch content of spinach

chinois. 研究不同铵硝比的氮素营养对于菠菜有机酸和淀粉含量的影响。采用营养液栽培菠菜的方法，营养液中的氮素形态设置硝态氮和铵态氮以一定比例（100s0、75s25、50s50、25s75 和 0s100）配合。随着铵硝比的下降，（1）菠菜茎叶丙酮酸、柠檬酸、α-酮戊二酸、琥珀酸、延胡索酸和苹果酸等6种有机酸含量以及淀粉含量都呈上升趋势；同时，有机酸含量与营养液中初始硝态氮浓度之间呈显著的线性正相关关系；（2）菠菜根系丙酮酸、柠檬酸、琥珀酸和苹果酸含量以及淀粉含量也呈上升趋势，但延胡索酸含量的变化不明显；（3）除了柠檬酸外，菠菜根系其它5种有机酸含量与其茎叶中相应有机酸含量的比值都呈现下降的趋势；在全硝营养条件下，根系中只有琥珀酸和延胡索酸的含量低于其在茎叶中的含量；而在全铵营养时，菠菜根系中上述5种有机酸的含量均明显高于茎叶中的相应有机酸的含量。因此，与根系相比，菠菜茎叶中5种有机酸含量随营养液中硝态氮比例增加而增加的幅度更明显。而随着营养液中硝态氮比例的增加，菠菜根系柠檬酸含量与其茎叶柠檬酸含量的比值逐渐升高，则说明根系柠檬酸含量增加的幅度要大于茎叶柠檬酸含量；（4）菠菜的茎叶和根系中的淀粉含量都呈现下降的趋势，且与营养液中硝态氮浓度之间均呈现为显著的负相关关系。随着营养液中硝态氮比例的增加，菠菜茎叶和根系有机酸代谢均表现为增强的趋势。

anglais. Research was carried out to study the effect of ammonium-enhancement nutrition on organic acid and starch content in spinach (Spinacia oleracea L.). Hydroponic experiments were conducted in greenhouse, nitrogen form changed by properly increasing ammonium concentration in nutrient solution. Content of pyravate, citrate, α-ketoglutarate, succinate, fumarate and malate in spinach shoots increased with the decrease of NH4+-N/NO3--N ratio, and which were significantly and positively correlated with nitrate concentration in nutrient solution. The content of pyravate, citrate, succinate and malate in spinach roots also increased with the decrease of NH4+-N/NO3--N ratio, which didn’t significantly affect fumarate content. With the decline of NH4+-N/NO3--N ratios, ratios of pyravate, α-ketoglutarate, succinate, fumarate and malate content of roots to that of shoots in spinach tended to decrease, while the ratio of citrate content gradually increased. Starch content in both of shoot and root in spinach tended to decrease with the decrease of NH4+-N/NO3--N ratio, and starch content in both of shoots and roots were negatively correlated with the nitrate concentration in nutrient solution. With the increase of proportion of nitrate supply in nutrient solution, metabolism of organic acids in both of shoot and root enhanced to provide enough energy and carbon skeleton for protein synthesis.