Henriksen G. H., Spanswick R. M.
Section of Plant Biology, Division of Biological Sciences, Cornell University, Ithaca, New York 14853.
Plant Physiol. 1993 Nov;103(3):885-892. doi: 10.1104/pp.103.3.885.
The influence of a 12-h pretreatment with either NO3-, NH4+, glutamine, or glutamate (300 [mu]M) on the apparent induction of NO3- uptake was investigated. Net fluxes of NO3- into roots of intact, 7-d-old barley (Hordeum vulgare L. cv Prato) seedlings in solution culture were estimated from ion activity gradients measured with NO3--selective microelectrodes in the unstirred layer of solution immediately external to the root surface. Control plants, pretreated with nitrogen-free nutrient solution, exhibited a sigmoidal increase in net NO3- uptake, reaching a maximum rate between 8 and 9 h after first exposure to NO3-. Plants pretreated with NH4+ or Glu exhibited a delay of several hours in the initiation of the induction process after they had been exposed to NO3-. In Gln-pretreated plants, however, responses ranged from no delay of the induction process to delays comparable to those observed following NH4+ or Glu pretreatments. Only treatment with NO3-resulted in the induction of NO3- uptake, whereas pretreatments with NH4+, Gln, or Glu tended to delay induction of NO3- uptake upon subsequent exposure to NO3-.
研究了用NO₃⁻、NH₄⁺、谷氨酰胺或谷氨酸(300μM)进行12小时预处理对NO₃⁻吸收表观诱导的影响。通过用NO₃⁻选择性微电极测量完整的7日龄大麦(Hordeum vulgare L. cv Prato)幼苗根系在溶液培养中,根表面外无搅拌溶液层中的离子活性梯度,来估算NO₃⁻进入根系的净通量。用无氮营养液预处理的对照植株,其净NO₃⁻吸收呈S形增加,在首次接触NO₃⁻后8至9小时达到最大速率。用NH₄⁺或Glu预处理的植株在接触NO₃⁻后,诱导过程的起始延迟了数小时。然而,在谷氨酰胺预处理的植株中,反应范围从诱导过程无延迟到与NH₄⁺或Glu预处理后观察到的延迟相当。只有用NO₃⁻处理导致了NO₃⁻吸收的诱导,而用NH₄⁺、谷氨酰胺或Glu预处理在随后接触NO₃⁻时往往会延迟NO₃⁻吸收的诱导。