The role of amyloplasts in the interactions between hydrotropism and gravitropism has been previously described. However, the effect of light-dark on the interactions between the two tropisms remains unclear. Here, by developing a method that makes it possible to mimic natural conditions more closely than the conventional lab conditions, we show that hydrotropism is higher in wild-type Arabidopsis seedlings whose shoots are illuminated but whose roots are grown in the dark compared with seedlings that are fully exposed to light. Root gravitropism is substantially decreased because of the reduction of amyloplast content in the root tip with decreased gene expression in PGM1 (a key starch biosynthesis gene), which may contribute to enhanced root hydrotropism under darkness. Furthermore, the starch-deficient mutant pgm1-1 exhibits greater hydrotropism compared with wild-type. Our results suggest that amyloplast response and starch reduction occur under light-dark modulation, followed by decreased gravitropism and enhanced hydrotropism in Arabidopsis root.

淀粉体在亲水性和向重性之间的相互作用中的作用之前已经描述过。然而，明暗对两种趋向性之间相互作用的影响仍不清楚。在这里，通过开发一种方法，可以比传统的实验室条件更接近地模拟自然条件，我们表明野生型拟南芥幼苗的水溶性更高，这些幼苗的枝条被照亮但根部在黑暗中生长。完全暴露在光线下。由于PGM1基因表达降低，根尖淀粉质体含量减少，根向地性显着降低（一种关键的淀粉生物合成基因），这可能有助于在黑暗中增强根的亲水性。此外，与野生型相比，缺乏淀粉的突变体pgm1-1表现出更大的亲水性。我们的研究结果表明，淀粉体反应和淀粉减少发生在明暗调节下，随后是拟南芥根的向重性降低和亲水性增强。