Imai T, Kingston-Smith A H, Foyer C H
National Research Institute of Vegetables Ornamental Plants and Tea, Ano, Mie, Japan.
Free Radic Res. 1999 Dec;31 Suppl:S171-9. doi: 10.1080/10715769900301471.
Photosynthesis and leaf ascorbate were measured in potato (Solanum tuberosum L.) plants grown in low light and then transferred to high light. Total foliar ascorbate content in low light-grown plants was 4.72+/-0.42 micromol mg(-1)chl. Over 80% of the ascorbate pool was found in the reduced form irrespective of position on the stem. No statistically-significant light-dependent effects were observed. Leaf discs supplied with [14C]-ascorbate in the dark showed significant ascorbate uptake such that after a 16h incubation over half of the total ascorbate pool in the discs was labelled [14C]-ascorbate. No ascorbate efflux from the leaves occurred during the period of [14C]-ascorbate uptake. The total amount of ascorbate did not increase, however, implying modified ascorbate turnover. The turnover of the [14C]-ascorbate in the leaves occurred at similar rates in both light and darkness. Little degradation of labelled ascorbate was observed, suggesting that uptake of exogenous ascorbate leads to inhibition of de novo ascorbate biosynthesis in potato leaf discs.
对在弱光下生长然后转移到强光下的马铃薯（Solanum tuberosum L.）植株进行了光合作用和叶片抗坏血酸的测定。在弱光下生长的植株中，叶片总抗坏血酸含量为4.72±0.42微摩尔/毫克叶绿素。无论在茎上的位置如何，超过80%的抗坏血酸库以还原形式存在。未观察到统计学上显著的光依赖效应。在黑暗中供应[14C] -抗坏血酸的叶圆片显示出显著的抗坏血酸吸收，因此在孵育16小时后，叶圆片中超过一半的总抗坏血酸库被标记为[14C] -抗坏血酸。在[14C] -抗坏血酸吸收期间，叶片没有抗坏血酸外流。然而，抗坏血酸的总量没有增加，这意味着抗坏血酸周转发生了改变。叶片中[14C] -抗坏血酸的周转在光照和黑暗条件下以相似的速率发生。观察到标记的抗坏血酸几乎没有降解，这表明外源抗坏血酸的吸收导致马铃薯叶圆片中从头抗坏血酸生物合成受到抑制。
