Studies on the Japanese Barnyard Millet as Soiling Crop : III. Mesocotyl elongation in Japanese barnyard millet seedling

Abstract

The elongation of mesocotyl of Japanese barnyard millet (Echinochloa utilis Ohwi et Yabuno) seedling was remarkable and attained to about 13 cm, though the coleoptile was only about 0.5 cm in length at 30°C in the dark. Decapitation of coleoptile remarkably inhibited the elongation of mesocotyl in proportion to the extent of decapitation. Eluted sections of paper chromatograms from ether extract of coleoptiles of Japanese barnyard millet were used to characterize the growth response of wheat coleoptile sections. At Rf values of 0.1∼0.2, 0.4 and 0.9 in acid fraction an increase of wheat coleoptile elongation was observed, with the increase of 25∼45 per cent over the control. The effects of gibberellin (GA), indole-3-acetic acid (IAA), 2, 3, 5-triiodobenzoic acid (TIBA) and trans-cinnamic acid (TCA) on the growth of seedlings by treatment to sowing bed were tested. GA (1∼1OOppm) had no effect on elongation of mesocotyl. IAA had a little stimulation on the elongation of coleoptile with 10^-6M, but mesocotyl elongation was inhibited with 10^-5M and 10^-6M. TIBA considerably increased the coleoptile elongation with 17.5 ppm, and conversely inhibited the mesocotyl elongation with the same concentration. TCA had also the same effect, although the effect was not remarkable as well as TIBA. GA(10∼1000 ppm) had no promotive effect on elongation of mesocotyl sections. IAA had promotive effect on elongation of mesocotyl sections at the concentration of 10^-M and 10^-6M. TIBA(1∼10 ppm) had an inhibitory effect on mesocotyl elongation and a stimulative effect on coleoptile elongation in the sections contained both coleoptile and mesocotyl. As the results of marking method and microscopic observation, it became clear that the growing region of mesocotyl was limitted narrow range of about 2 mm lower the coleoptilar node, and the growth of mesocotyl depend on the both cell division and cell elongation