Armstrong M J, Kirkby E A
Department of Plant Sciences, The University of Leeds, Leeds LS2 9JT England.
Plant Physiol. 1979 Jun;63(6):1143-8. doi: 10.1104/pp.63.6.1143.
A procedure to estimate the extent of K recirculation in plants is proposed. This is based on the ratio of the upward fluxes of K to Ca in the xylem sap from root to shoot with the ratio of K to Ca accumulation in plant tops.In a preliminary investigation the factors influencing the K to Ca ratio in the xylem sap were considered. Tomato plants were grown at three levels of K nutrition and harvested at different times during the 24-hour day period. It was shown that the K to Ca ratio in xylem sap changed dramatically depending on the time of sap collection after decapitation, the values falling from over 2 to less than unity over the 4-hour period of collection. Diurnal effects on exudation were less marked but also of significance. The level of K nutrition was of little importance. It is suggested that a representative xylem sap from tomato plants can best be obtained from samples taken between 15 and 60 minutes after decapitation.In a second experiment K recirculation was estimated. At nine harvesting stages over a 24-hour period the K to Ca ratio in the xylem sap was invariably higher than the K to Ca ratio of accumulation in the tops over the same period. From this information it was calculated that about 20% of the upward flux of K in the xylem stream resulted from recirculated K.
本文提出了一种估算植物中钾再循环程度的方法。该方法基于从根部到地上部的木质部汁液中钾与钙向上通量的比值以及植物地上部钾与钙积累量的比值。在初步研究中，考虑了影响木质部汁液中钾钙比的因素。番茄植株在三种钾营养水平下生长，并在一天24小时内的不同时间收获。结果表明，木质部汁液中钾钙比在去头后采集汁液的时间不同时变化显著，在4小时的采集期内，该比值从超过2降至小于1。昼夜对渗出的影响不太明显，但也很重要。钾营养水平不太重要。建议从去头后15至60分钟采集的样本中最好地获取番茄植株具有代表性的木质部汁液。在第二个实验中估算了钾的再循环。在24小时内的九个收获阶段，木质部汁液中的钾钙比始终高于同一时期地上部积累的钾钙比。根据这些信息计算得出，木质部流中钾向上通量的约20%来自再循环的钾。
