The Yield Formation Process Viewed from the Development of the Sink and Source of Individual Shoots in the Rice Plant : II. Formation, degeneration and survival of rachis-branches and flower primordia at individual primary rachis-branches differing in the position on a rachis

[摘要] Using shoots having shoot vigor rank (SVR) 1, 5 and 9 in part I, the aspects of development of rachis-branches and flower primordia (FP) were examined at the level of individual primary rachis-branches (PRB)in relation to their positions on the rachis. (i) The lower the SVR, the fewer the FP of the panicle because of the fewer PRB on a panicle and the fewer FP on a PRB. (ii) In all the shoots, percentage degeneration (PD) for PRB, secondary rachis-branch (SRB) on surviving PRB, FP on surviving SRB, FP situated directly on surviving PRB and whole FP on a PRB was all largest at the basal PRB and decreased with rising PRB position on the rachis. (iii) Comparing the PRB situated at the equivalent position, the lower the SVR, the higher was PD for PRB and FP on surviving SRB, while that for SRB on surviving PRB, FP situated directly on surviving PRB and whole FP on the PRB was nearly constant among shoots. However, PD based on the numbers for the whole panicle was larger also in the latter three in the weaker stems because they have less upper PRB in which degeneration scarcely occurs. (iv) The lower the SVR, the smaller was the proportion of surviving flowers on SRB to the total surviving ones almost evenly at each PRB on a panicle.

[学科分类] 农业科学（综合）

[关键词] Flower primordia degeneration;イネ;Flower primordia formation;穎花原基の退化;Panicle structure;穎花原基の分化;Rachis-branch;茎の強勢度;Rice plant;枝梗;Shoot vigor;穂の構造;Sink/source ratio