Department of Botany, Norwegian University of Science and Technology, N-7491 Trondheim, Norway;
Am J Bot. 2002 Oct;89(10):1604-8. doi: 10.3732/ajb.89.10.1604.
Evidence of adaptation in Arabidopsis thaliana (Brassicaceae) phenotypic traits has rarely been shown. We demonstrate latitudinal clines in two A. thaliana traits: hypocotyl responses to red and far-red light. Natural populations of A. thaliana were sampled along a latitudinal gradient from southern to northern Norway. Seeds from maternal families within each population were subjected to 1 wk of constant red, far-red, blue, white, and dark treatments. Hypocotyl lengths were measured for each maternal family within each population. Significant variability within and among populations in hypocotyl responses for the various treatments was found. There was a significant latitudinal cline in hypocotyl responses for red and far-red treatments, with northern populations being more de-etiolated than southern populations. These results suggest that northern populations are more responsive to red and far-red light than southern populations. Thus, differentiation of seedling traits in natural populations of A. thaliana seems in part to be mediated by the phytochrome pathway. There was no correlation between hypocotyl responses and flowering time for any treatment. This suggests that flowering time variability and variability in hypocotyl responses may not be governed by genes shared between the pathways, such as those involved in photoreception or the circadian clock.
在拟南芥（十字花科）表型特征中很少有适应证据的报道。我们展示了拟南芥两个特征的纬度梯度：下胚轴对红光和远红光的反应。从挪威南部到北部的纬度梯度上，我们从自然种群中采集了拟南芥的种子。在每个种群内的母系家族中，种子接受了为期 1 周的恒定红光、远红光、蓝光、白光和黑暗处理。在每个种群的每个母系家族中测量了下胚轴的长度。发现各种处理的下胚轴反应在种群内和种群间具有显著的可变性。红光和远红光处理的下胚轴反应有显著的纬度梯度，北部种群比南部种群去黄化程度更高。这些结果表明，与南部种群相比，北部种群对红光和远红光的反应更敏感。因此，拟南芥自然种群中幼苗特征的分化部分似乎是由光敏素途径介导的。对于任何处理，下胚轴反应与开花时间都没有相关性。这表明，开花时间的变异性和下胚轴反应的变异性可能不受光受体或生物钟途径之间共享基因的控制。
