Centro de Investigaciones Biológicas Margarita Salas - CSIC, Madrid, Spain.
Physiol Plant. 2022 May;174(3):e13722. doi: 10.1111/ppl.13722.
In a microgravity environment, without any gravitropic signal, plants are not able to define and establish a longitudinal growth axis. Consequently, absorption of water and nutrients by the root and exposure of leaves to sunlight for efficient photosynthesis is hindered. In these conditions, other external cues can be explored to guide the direction of organ growth. Providing a unilateral light source can guide the shoot growth, but prolonged root exposure to light causes a stress response, affecting growth and development, and also affecting the response to other environmental factors. Here, we have investigated how the protection of the root from light exposure, while the shoot is illuminated, influences the direction of root growth in microgravity. We report that the light avoidance mechanism existing in roots guides their growth towards diminishing light and helps establish the proper longitudinal seedling axis in simulated microgravity conditions. This process is regulated by flavonols, as shown in the flavonoid-accumulating mutant transparent testa 3, which shows an increased correction of the root growth direction in microgravity, when the seedling is grown with the root protected from light. This finding may improve the efficiency of water and nutrient sourcing and photosynthesis under microgravity conditions, as they exist in space, contributing to better plant fitness and biomass production in space farming enterprises, necessary for space exploration by humans.
在微重力环境中，没有任何向地性信号，植物无法确定和建立纵向生长轴。因此，根吸收水分和养分以及叶片暴露在阳光下进行高效光合作用会受到阻碍。在这些条件下，可以探索其他外部线索来引导器官生长的方向。提供单侧光源可以引导芽的生长，但长时间的根暴露在光线下会引起应激反应，影响生长和发育，也会影响对其他环境因素的反应。在这里，我们研究了在微重力条件下，保护根免受光照，而芽被照亮时，如何影响根的生长方向。我们报告说，存在于根中的避光机制引导其向光减少的方向生长，并有助于在模拟微重力条件下建立适当的纵向幼苗轴。这个过程受到类黄酮的调节，如在类黄酮积累突变体透明种皮 3 中所示，当幼苗在根受到保护而免受光照的情况下生长时，它会增加在微重力下纠正根生长方向的能力。这一发现可能会提高在微重力条件下水和养分的获取以及光合作用的效率，因为它们在太空中存在，有助于提高太空农业企业中植物的适应性和生物量生产，这对于人类的太空探索是必要的。
