水稲の重力成形に関する作物学的研究（Ⅲ）

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1. Indoleacetic acid (IAA) applied to the rice plants kept in a vertical position increased the number of roots, but not the total length of roots. On the other hand, IAA applied to the culm pieces with a node and the base of leaf sheath increased the total length of roots as well as the root number ; such effects were also seen in the culms merely horizontally fixed. IAA had effects similar to the gravitational stimulation on the top growth and the inclination angle of lamina; the former was inhibited and the latter enlarged at the upper site in the rice plants horizontally kept. 2. In the rice plants grown in an oligotrophic state, IAA treatment in their booting stage led to acceleration in the growth of tiller buds at the lower nodes of the vertical stem and to retardation in it at the middle and upper nodes. It lengthened the internodes at the middle site of the vertical stem, and it elongated the internodes even at the upper site in the rice plants laminae of which were cut off. IAA applied to the rice plants vertically kept caused the same effects as those of unilateral stimulation of gravity on the growth of tiller buds and the elongation of internodes. 3. The rice plants grown in poor nutrition and of putting forth the 9th leaf were grouped into two plots, vertical and horizontal. Each of them was allowed to absorb IAA-14C solution through the 8th leaf for 3 hours, and an amount of unmetabolized IAA-14C contained in the stem extending from the 4th leaf node to just below the 8th was compared between the two plots; IAA-14C was distributed at the ratio of 40 to 60 after 0 hour, and of 32 to 68 after 3 hours between the upper and lower sides of the stem in the horizontal plot, while it was at the equal ratio after each time between right and left sides of the stem in the vertical. On the other hand, the amount of IAA-14C contained in the stem examined (it was not different between the two plots after 0 hour) after 3 hours was as much as 7% in the horizontal plot, while the amount of IAA-14C metabolites was found more largely in the vertical. 4. The pieces of culms with a node and the base of leaf sheath were, in their upright state, allowed to absorb tryptophan-14C solution for 3 hours, and then they were grouped into the horizontal and vertical plots which were kept under a dark condition for a some time. The comparison between the two plots was made on the amount of biosynthesized IAA-14C ; it was larger in the horizontal plot by 23～12% through various periods ranging from 3 to 24 hours than in the vertical, showing the former exceeded the latter in auxin synthesizing capability. In the basal part of the horizontal culms, IAA-14C was asymmetrically distributed between the upper and lower sides, and such a difference diminished after 12 hours. 5. All the results obtained indicate that unilateral stimulation of gravity accelerates biosynthesis of auxin to elevate its concentration in the rice plants, in addition to the effect of bringing about an asymmetrical distribution of auxin between the upper and lower sides of the plants as already confirmed. Consequently, in the rice plants laid in a horizontal position with their axes, the auxin concentrations become superoptimal for the growth in the apical part, thus causing it to retard, whereas they become optimal both for the internodal elongation in the middle site and for the rooting and the growth of tiller buds in the basal part.
奈良教育大学の論文
1978-11-25

著者

石井滋規
奈良教育大

水稲の重力成形に関する作物学的研究（Ⅲ）

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