Institut Phytosphere (ICG-3), Forschungszentrum Jülich GmbH, Jülich, Germany.
Plant Cell Environ. 2010 Mar;33(3):408-17. doi: 10.1111/j.1365-3040.2009.02090.x. Epub 2009 Nov 24.
In laboratory and greenhouse experiments with potted plants, shoots and roots are exposed to temperature regimes throughout a 24 h (diel) cycle that can differ strongly from the regime under which these plants have evolved. In the field, roots are often exposed to lower temperatures than shoots. When the root-zone temperature in Ricinus communis was decreased below a threshold value, leaf growth occurred preferentially at night and was strongly inhibited during the day. Overall, leaf expansion, shoot biomass growth, root elongation and ramification decreased rapidly, carbon fluxes from shoot to root were diminished and carbohydrate contents of both root and shoot increased. Further, transpiration rate was not affected, yet hydrostatic tensions in shoot xylem increased. When root temperature was increased again, xylem tension reduced, leaf growth recovered rapidly, carbon fluxes from shoot to root increased, and carbohydrate pools were depleted. We hypothesize that the decreased uptake of water in cool roots diminishes the growth potential of the entire plant - especially diurnally, when the growing leaf loses water via transpiration. As a consequence, leaf growth and metabolite concentrations can vary enormously, depending on root-zone temperature and its heterogeneity inside pots.
在盆栽植物的实验室和温室实验中，芽和根暴露在 24 小时（昼夜）周期内的温度条件下，这些条件与这些植物进化过程中的条件有很大的不同。在野外，根通常暴露在比芽更低的温度下。当蓖麻的根区温度降低到一个阈值以下时，叶片生长优先在夜间发生，白天受到强烈抑制。总的来说，叶片扩展、茎生物量生长、根伸长和分枝迅速减少，从茎到根的碳通量减少，根和茎的碳水化合物含量增加。此外，蒸腾速率不受影响，但茎木质部的静水压力增加。当根温再次升高时，木质部张力降低，叶片生长迅速恢复，从茎到根的碳通量增加，碳水化合物库被耗尽。我们假设，凉爽的根对水分的吸收减少会降低整个植物的生长潜力——尤其是在白天，生长中的叶子通过蒸腾作用失去水分时。因此，叶片生长和代谢物浓度会根据根区温度及其在盆内的异质性而发生巨大变化。
