Tomoki Hoshino

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

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.

Chemical compositions of exudates from succulent plants induced by methyl jasmonate

AbstractMethyl jasmonate (JA-Me) promoted leaf abscission of succulent plant, Crassula lycopodioides, and exudation from stems and leaves after leaf abscission when it was sprayed in whole plants. Major component of the exudate was identified as sucrose based on the results described below.(1)The reaction of the excudate was not positive in the Somogyi-Nelson method but in the phenol-sulfuric acid method.(2)The exudate was hydrolyzed with invertase of Candida utilis, after that showing a positive reaction in the Somogyi-Nelson method.(3)Only glucose and mannose were identified in the exudate after hydrolysis with trifluoroacetic acid using a gas-liquid chromatograph (GLC).(4)A single peak corresponding to the retention time of sucrose was observed using a high performance liquid chromatograph (HPLC). In addition, potassium and sodium were found in the exudate as major inorganic cations. These results suggest that exudate of Crassula lycopodioides is phloem sap, and JA-Me promotes the excudation due to the inhibition of the synthesis of callose in sieve tubes of succulent plants.