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Enzymatic responses of cucumber roots to different levels of Fe supply

机译：黄瓜根对不同铁水平的酶促反应

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Development of the coordinated response to decreasing Fe availability was studied in cucumber plants grown in nutrient solution (NS) over a range of FeIII-EDTA concentrations (from 0.1 to 80 μM). Physiological and biochemical parameters were evaluated in intact roots, root extracts and plasma membrane (pm) vesicles. Acidification of the NS was evident in plants grown at ≤ 1 μM FeIII-EDTA and inversely related to the external Fe concentration. FeIII-EDTA reduction by intact roots was also gradually depressed by increasing Fe supply. The rate of net nitrate uptake by the roots was directly related to the amount of FeIII-EDTA added to the NS. Activity of pmH+-ATPase was significantly higher in plants grown without added Fe as compared to those grown at 80 μM Fe. A lower increase, dependent on Fe concentration, was observed at 0.1, 1, 5 or 10 μM FeIII-EDTA. Activity of pmFeIII-EDTA reductase was also increased by Fe deprivation and strongly correlated with pmH+-ATPase activity. PEP-carboxylase activity gradually increased with decreasing Fe concentration in the NS. Changes in activity and amount of the enzyme showed a close correlation with parameters measured in intact roots (nitrate uptake, FeIII-EDTA reduction). Results show that the development of the Fe-deficiency response in cucumber roots can be finely tuned by the level of Fe supply. Adjustments to different levels of available Fe involve a correlated modulation of pm-associated enzymes. PEP-carboxylase activity appeared to be a suitable metabolic marker of the Fe nutritional status of the plant.
机译：研究了在营养液（NS）中生长的FeIII -EDTA浓度范围（0.1至80μM）下黄瓜植株对减少Fe有效性的协调反应的发展。在完整的根，根提取物和质膜（pm）囊泡中评估生理和生化参数。在≤1μMFeIII -EDTA的植物中，NS的酸化现象明显，并且与外部Fe浓度成反比。完整根系对FeIII -EDTA的还原作用也随着Fe供应的增加而逐渐降低。根部吸收硝酸盐的净率与添加到NS中的FeIII -EDTA的量直接相关。与80μMFe相比，不添加Fe的植物中pmH + -ATPase的活性明显更高。在0.1、1、5或10μM的FeIII -EDTA中观察到较低的增加，这取决于Fe的浓度。剥夺铁还增加了pmFeIII -EDTA还原酶的活性，并且与pmH + -ATPase的活性密切相关。随着NS中Fe浓度的降低，PEP羧化酶活性逐渐增加。酶的活性和数量的变化与完整根中的参数（硝酸盐吸收，FeIII -EDTA还原）密切相关。结果表明，可以通过铁的供应水平微调黄瓜根中铁缺乏反应的发展。对不同水平的可用铁的调节涉及与pm相关的酶的相关调节。 PEP-羧化酶活性似乎是植物铁营养状况的合适代谢指标。

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