Steer B T
Division of Irrigation Research, Commonwealth Scientific and Industrial Research Organisation, Griffith, N.S.W., 2680, Australia.
Plant Physiol. 1976 Jun;57(6):928-32. doi: 10.1104/pp.57.6.928.
In the expanding leaves of Capsicum annuum L. cv. California Wonder, two of the three peaks of nitrate reductase activity associated with the light period exhibit a circadian rhythm that persists in continuous light.The spray application of kinetin to the whole shoot or to leaves other than the ones used for nitrate reductase assay causes a phase shift in the activity peaks and this has been used in preliminary investigations of the character of the mechanisms controlling the timing of the peaks.There was some indication that the rate of translocation of nitrate from the roots might be involved. The levels of nitrate moving up the stem after kinetin treatment were more dependent upon the rate of sap flow than on the concentration of nitrate in the sap. For this reason, transpiration rates in whole plants were measured after kinetin treatment but no change in pattern was seen that would correlate with the phase shift in nitrate reductase activity.The occurrence of nitrate reductase peaks in excised leaves suggested a leaf-based in addition to a root-or stem-based mechanism in the timing of nitrate reductase activity in the leaves.
在甜椒（Capsicum annuum L. cv. California Wonder）展开的叶片中，与光照期相关的硝酸还原酶活性的三个峰值中的两个呈现出昼夜节律，且在持续光照下依然存在。向整株植株或用于硝酸还原酶测定的叶片以外的其他叶片喷施激动素，会导致活性峰值出现相位偏移，这已被用于对控制峰值时间的机制特性进行初步研究。有迹象表明，根部硝酸盐的转运速率可能与之有关。激动素处理后向上运输到茎部的硝酸盐水平，更多地取决于汁液流动速率，而非汁液中硝酸盐的浓度。因此，在激动素处理后测量了整株植物的蒸腾速率，但未观察到与硝酸还原酶活性相位偏移相关的模式变化。离体叶片中硝酸还原酶峰值的出现表明，除了基于根或茎的机制外，叶片中硝酸还原酶活性的时间调控还存在基于叶片的机制。
