Growth and Development, and Auxin Polar Transport in Higher Plants under Microgravity Conditions in Space: BRIC-AUX on STS-95 Space Experiment

Abstract

The principal objectives of the space experiment, BRIC-AUX on STS 95, were the integrated analysis of the growth and development of etiolated pea and maize seedlings in space and a study of the effects of microgravity conditions in space on auxin polar transport in these segments. Microgravity significantly affected the growth and development of etiolated pea and maize seedlings. Epicotyls of etiolated pea seedlings were the most oriented toward about 40 to 60 degrees from the vertical. Mesocotyls of etiolated maize seedlings were curved at random during space flight but coleoptiles were almost straight. Finally the growth inhibition of these seedlings in space was also observed. Roots of some pea seedlings grew toward to the aerial space of Plant Growth Chamber. Extensibilities of cell walls of the third internode of etiolated pea epicotyls and the top region of etiolated maize coleoptiles, which were germinated and grown under microgravity conditions in space, were significantly low as compared with those grown on the ground of the earth. Activities of auxin polar transport in the second internode segments of etiolated pea seedlings and coleoptile segments of etiolated maize seedlings were significantly inhibited and promoted, respectively, under microgravity conditions in space. These results strongly suggest that auxin polar transport as well as the growth and development of plants is controlled under gravity on the earth.

Growth and Morphogenesis of Azuki Bean Seedlings in Space during SSAF2013 Program

“…Heathcote et al (1995) showed that wheat coleoptiles oriented away from the caryopsis (abaxial). Pea epicotyls also oriented abaxial direction (Ueda et al, 1999). On the other hand, rice coleoptiles bended adaxial direction toward the caryopsis (Hoson et al, 1999).…”

“…These results indicate that growth pattern of shoots in space is different by plant species and by the type of organs. Epicotyls of both pea (Ueda et al, 1999) and azuki bean (Fig. 1) elongated abaxially in space.…”

“…In a stimulus-free environment, such as space, plants show spontaneous morphogenesis, termed automorphosis or automorphogenesis (Hoson et al, 1999). For example, pea epicotyls oriented oblique upward direction away from the cotyledons, and roots oriented upward asymmetric to the epicotyls in space (Ueda et al, 1999).…”

Auxin Polar Transport is Essential for the Early Growth Stage of Etiolated Maize (Zea maysL. cv. Honey Bantam) Seedlings

“…Auxin polar transport was determined according to the method reported previously (Oka et al, 1995;Ueda et al, 1999Ueda et al, , 2000Ueda et al, , 2012Ueda et al, , 2013Hoshino et al, 2007) , American Radiolabeled Chemicals Inc., St. Louis, Mo.) was prepared in 1.5 ml Eppendorf tubes, and was incorporated into the apical or the basal side of the segments in the tube.…”

Preparation and Outline of Space-Based Studies on Gravity Responses and Cell Wall Formation in Plants

“…These circumstances can involve a three-dimensional clinostat for simulating microgravity, an agravitropic mutant, or the microgravity conditions of space or parabolic flight. A number of Japanese studies on plant gravitational biology have been conducted aboard the space shuttle, and considerable information about graviperception, growth, and gravimorphogenesis has been obtained (Hoson et al, 1999;Takahashi et al, 2000;Ueda et al, 1999;Wolverton et al, 1999).…”