We analyzed the changes in growth and cell wall properties of roots of rice (Oryza sativa L. cv. Koshihikari) grown for 68.5, 91.5, and 136 h during the Space Shuttle STS-95 mission. In space, most of rice roots elongated in a direction forming a constant mean angle of about 55° with the perpendicular base line away from the caryopsis in the early phase of growth, but later the roots grew in various directions, including away from the agar medium. In space, elongation growth of roots was stimulated. On the other hand, some of elasticity moduli and viscosity coefficients were higher in roots grown in space than on the ground, suggesting that the cell wall of space-grown roots has a lower capacity to expand than the controls. The levels of both cellulose and the matrix polysaccharides per unit length of roots decreased greatly, whereas the ratio of the high molecular mass polysaccharides in the hemicellulose fraction increased in space-grown roots. The prominent thinning of the cell wall could overwhelm the disadvantageous changes in the cell wall mechanical properties, leading to the stimulation of elongation growth in rice roots in space. Thus, growth and the cell wall properties of rice roots were strongly modified under microgravity conditions during spaceflight.

中文翻译：

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太空飞行过程中水稻根系的生长和细胞壁变化

我们分析了在 STS-95 航天飞机任务期间生长 68.5、91.5 和 136 小时的水稻（Oryza sativa L. cv. Koshihikari）根的生长和细胞壁特性的变化。在空间上，水稻的大部分根系在生长初期向远离颖果的垂直基线形成约55°的恒定平均角的方向伸长，但后来根向不同方向生长，包括远离琼脂中等的。在空间中，根系的伸长生长受到刺激。另一方面，空间生长的根的一些弹性模量和粘度系数高于地面，这表明空间生长的根的细胞壁扩张能力低于对照。单位根长度纤维素和基质多糖的含量均显着降低，而半纤维素部分中高分子量多糖的比例在太空生长的根中增加。细胞壁的显着变薄可以克服细胞壁力学性能的不利变化，导致水稻根系空间伸长生长的刺激。因此，在太空飞行过程中，在微重力条件下，水稻根的生长和细胞壁特性发生了强烈的变化。