Department of Soil Science, North Carolina State University, Raleigh, North Carolina 27607.
Plant Physiol. 1972 Oct;50(4):485-90. doi: 10.1104/pp.50.4.485.
The absorption and assimilation patterns of (15)NO(3) (-) supplied as the Ca(2+) and Mg(2+) salts to intact ryegrass (Lolium perenne) seedlings were compared. No statistically significant effect of ambient cation on the amounts of (15)NO(3) (-) absorbed was observed in the initial six hours, but during the subsequent six hours, absorption from Ca((15)NO(3))(2) exceeded that from Mg ((15)NO(3))(2).Lower rates of (15)NO(3) (-) assimilation were found in roots exposed to Mg((15)NO(3))(2) than in those exposed to Ca((15)NO(3))(2). It was proposed that Mg(2+) initiated a restriction in (15)NO(3) (-) reduction in roots, probably as a consequence of a Mg(2+)-induced physiological Ca(2+) deficiency. Lower (15)N translocation rates were also observed from Mg((15)NO(3))(2). These effects of Mg(2+) in depressing (15)NO(3) (-) assimilation and translocation occurred prior to an effect on (15)NO(3) (-) uptake.In shoots, larger amounts of reduced (15)N products occurred with Ca((15)NO(3))(2) than with Mg((15)NO(3))(2). It was concluded that this was due to enhanced translocation of (15)NO(3) (-) (and possibly its reduced products) in presence of Ca(2+) rather than to specific cation effects on (15)NO(3) (-) assimilation in the shoots.
将以 Ca(2+)和 Mg(2+)盐形式提供的 (15)NO(3) (-) 的吸收和同化模式与完整黑麦草（Lolium perenne）幼苗进行了比较。在最初的六小时内，环境阳离子对吸收的 (15)NO(3) (-)量没有统计学上的显著影响，但在随后的六小时内，从 Ca((15)NO(3))(2)吸收的量超过了从 Mg ((15)NO(3))(2)吸收的量。暴露于 Mg((15)NO(3))(2)的根中的 (15)NO(3) (-)同化率较低，而暴露于 Ca((15)NO(3))(2)的根中的 (15)NO(3) (-)同化率较低。据提议，Mg(2+)引发了根中 (15)NO(3) (-)还原的限制，可能是由于 Mg(2+)诱导的生理性 Ca(2+)缺乏所致。从 Mg((15)NO(3))(2)中也观察到较低的 (15)N 转运率。这些 Mg(2+)对 (15)NO(3) (-)同化和转运的抑制作用发生在对 (15)NO(3) (-)吸收的影响之前。在地上部分，与 Mg((15)NO(3))(2)相比，用 Ca((15)NO(3))(2)产生了更多的还原的 (15)N 产物。结论是，这是由于在 Ca(2+)存在下增强了 (15)NO(3) (-)（可能还有其还原产物）的转运，而不是由于阳离子对地上部分 (15)NO(3) (-)同化的特定影响所致。
