Shimazu T, Yuda T, Miyamoto K, Yamashita M, Ueda J
College of Integrated Arts and Sciences, Osaka Prefecture University, Osaka, Japan.
Adv Space Res. 2001;27(5):995-1000. doi: 10.1016/s0273-1177(01)00165-x.
Growth and development of etiolated pea (Pisum sativum L. cv. Alaska) and maize (Zea mays L. cv. Golden Cross Bantam) seedlings grown under simulated microgravity conditions were intensively studied using a 3-dimensional clinostat as a simulator of weightlessness. Epicotyls of etiolated pea seedlings grown on the clinostat were the most oriented toward the direction far from cotyledons. Mesocotyls of etiolated maize seedlings grew at random and coleoptiles curved slightly during clinostat rotation. Clinostat rotation promoted the emergence of the 3rd internodes in etiolated pea seedlings, while it significantly inhibited the growth of the 1st internodes. In maize seedlings, the growth of coleoptiles was little affected by clinostat rotation, but that of mesocotyls was suppressed, and therefore, the emergence of the leaf out of coleoptile was promoted. Clinostat rotation reduced the osmotic concentration in the 1st internodes of pea seedlings, although it has little effect on the 2nd and the 3rd internodes. Clinostat rotation also reduced the osmotic concentrations in both coleoptiles and mesocotyls of maize seedlings. Cell-wall extensibilities of the 1st and the 3rd internodes of pea seedlings grown on the clinostat were significantly lower and higher as compared with those on 1 g conditions, respectively. Cell-wall extensibility of mesocotyls in seedlings grown on the clinostat also decreased. Changes in cell wall properties seem to be well correlated to the growth of each organ in pea and maize seedlings. These results suggest that the growth and development of plants is controlled under gravity on earth, and that the growth responses of higher plants to microgravity conditions are regulated by both cell-wall mechanical properties and osmotic properties of stem cells.
利用三维回转器作为失重模拟器，对在模拟微重力条件下生长的黄化豌豆（豌豆属阿拉斯加品种）和玉米（玉米属金皇后品种）幼苗的生长和发育进行了深入研究。在回转器上生长的黄化豌豆幼苗的上胚轴最倾向于远离子叶的方向。黄化玉米幼苗的中胚轴随机生长，在回转器旋转过程中胚芽鞘略有弯曲。回转器旋转促进了黄化豌豆幼苗第三茎节的出现，同时显著抑制了第一茎节的生长。在玉米幼苗中，回转器旋转对胚芽鞘的生长影响较小，但对中胚轴的生长有抑制作用，因此促进了叶片从胚芽鞘中伸出。回转器旋转降低了豌豆幼苗第一茎节中的渗透浓度，尽管对第二和第三茎节影响较小。回转器旋转也降低了玉米幼苗胚芽鞘和中胚轴中的渗透浓度。与1g条件下生长的豌豆幼苗相比，在回转器上生长的豌豆幼苗第一和第三茎节的细胞壁伸展性分别显著降低和升高。在回转器上生长的幼苗中胚轴的细胞壁伸展性也降低。细胞壁特性的变化似乎与豌豆和玉米幼苗各器官的生长密切相关。这些结果表明，地球上植物的生长和发育受重力控制，高等植物对微重力条件的生长反应受干细胞的细胞壁力学特性和渗透特性的调节。
