硝酸还原酶在植物中的作用是什么?急用!

硝酸还原酶是诱导酶,光照是其诱导条件之一,所以应在光合作用进行了一段时间以后（3h）采样,田间采样应在早晨9点钟以后.

The nitrate had accumulated the healthy key factor already have become the quality affecting vegetable,and affecting human being within the plant body,hydrogen nitrate reductase key enzyme in being that the nitrate metabolizes ,nitrate beneficial to improving whose activity degradation.The main body of a book is adopt to follow different condition of admeasurement in vitro to active effect of stem tumour mustard hydrogen nitrate reductase.Different course the different pH ,the different temperature ,different time ,different potassium nitrate thickness and hydrogen nitrate reductase thickness of tumour mustard hydrogen nitrate reductase treatment indicates a stem:The most suitable stem tumour mustard hydrogen nitrate reductase pH is 6.8; The most suitable temperature is 25 C; The most suitable bottom thing potassium nitrate thickness is mol/L ,thickness is relatively sufficient in stem tumour mustard hydrogen nitrate reductase when big ,stem tumour mustard hydrogen nitrate reductase activity rises gradually with the fact that bottom thing thickness increases by.Reaction condition exceeds or the enzymatic activity city accepts when being unable to reach the most suitable condition restraint.Simultaneous ,be enough in bottom thing potassium nitrate thickness when big,under lower condition of relative enzyme liquid thickness,the relative thickness increasing enzyme liquid gradually ,relative with hydrogen nitrate reductase reaction speed thickness increasing by but increase by,the enzyme reaction rate increases by also with that.Keywords:Hydrogen nitrate reductase pH temperature time potassium nitrate thickness activator depresso

解题思路：考查某些无机盐离子的生理作用，细胞中大多数无机盐以离子的形式存在，分析答题．

无机盐离子的作用有：（1）维持细胞和生物体的生命活动有重要作用；（2）维持细胞的酸碱平衡；（3）维持细胞的渗透压．（4）无机盐对维持细胞的形态和功能有重要作用等．Mn²⁺能够激活硝酸还原酶，使硝酸发生化学变化后被植物体利用．这说明Mn²⁺对于维持生物体的生命活动有重要作用，而不是无机盐的其他三项生理作用．
故选：B

点评：
本题考点： 无机盐的类型及其对植物的作用．

考点点评： 解答此题的关键是掌握无机盐离子的作用，结合题中的资料分析，即能正确答题．