Allen Joan, Bisbee Patricia A, Darnell Rebecca L, Kuang Anxiu, Levine Lanfang H, Musgrave Mary E, van Loon Jack J W A
Department of Plant Science, University of Connecticut, Storrs, Connecticut 06269 USA.
Am J Bot. 2009 Mar;96(3):652-60. doi: 10.3732/ajb.0800261.
How gravity influences the growth form and flavor components of plants is of interest to the space program because plants could be used for food and life support during prolonged missions away from the planet, where that constant feature of Earth's environment does not prevail. We used plant growth hardware from prior experiments on the space shuttle to grow Brassica rapa and Arabidopsis thaliana plants during 16-d or 11-d hypergravity treatments on large-diameter centrifuge rotors. Both species showed radical changes in growth form, becoming more prostrate with increasing g-loads (2-g and 4-g). In Brassica, height decreased and stems thickened in a linear relationship with increasing g-load. Glucosinolates, secondary compounds that contribute flavor to Brassica, decreased by 140% over the range of micro to 4-g, while the structural secondary compound, lignin, remained constant at ∼15% (w/w) cell wall dry mass. Stem thickening at 4-g was associated with substantial increases in cell size (47%, 226%, and 33% for pith, cortex, and vascular tissue), rather than any change in cell number. The results, which demonstrate the profound effect of gravity on plant growth form and secondary metabolism, are discussed in the context of similar thigmostresses such as touch and wind.
重力如何影响植物的生长形态和风味成分是太空计划所关注的问题，因为在远离地球的长期任务中，植物可用于提供食物和维持生命支持，而地球上这种恒定的环境特征在太空中并不存在。我们使用了先前航天飞机实验中的植物生长硬件，在大直径离心机转子上对芜菁和拟南芥进行了16天或11天的超重力处理。两个物种的生长形态都发生了根本性变化，随着重力负荷增加（2g和4g）变得更加匍匐。在芜菁中，高度降低，茎变粗，与重力负荷增加呈线性关系。硫代葡萄糖苷是赋予芜菁风味的次生化合物，在微重力到4g的范围内减少了140%，而结构性次生化合物木质素在细胞壁干质量中保持在约15%（w/w）不变。4g时茎变粗与细胞大小显著增加有关（髓、皮层和维管组织分别增加47%、226%和33%），而不是细胞数量的任何变化。本文结合触摸和风力等类似的接触胁迫，讨论了这些结果，这些结果证明了重力对植物生长形态和次生代谢的深远影响。
