Abstract
Wheat (Triticum aestivum L.) yields often are closely related to the sowing rate and the number of tillers on a plant. This study was conducted to examine the morphological features of whole plant and main stem, their relationships with the number of tillers, and the effects of environmental conditions. Winter wheat plants, cv. Norin 61 grown on dry (D, notirrigated), wet (W, irrigated) conditions in a vinyl-house and under field (F) conditions were sampled at maturity. The number of tillers per plant and 11 characteristics about ear, stem, rooting nodes, and roots were measured. The data was analysed by principal component analysis (PCA) and correlation analysis (CA). The results are as follows. (1) The results of PCA of whole plants showed that the first component, which was interpreted as a "size" factor, explained 94.4% of the observed variations. This indicated that the morphological feature of whole plant could be represented by the "size" factor. The results of CA showed that the "size" ot whole plant was determined primarily by the number of tillers. (2) The results of PCA of main stems showed that the morphological features of a main stem could be represented by the factors of "size" (53.2%), "ratio of aerial parts to subterranean parts" (17.1%), and "shape of stem axis" (10.1%). The subsequent CA suggested a positive correlation between the "size" of the main stem and the number of tillers. (3) The relationships between the "size" of main stem and the number of tillers were different amont the three experimental plots. This result indicated that environmental conditions exerted a direct effects on tiller formation in addition to those affecting the "size" of the main stem.
