Studies on Growth and Development of Tillers in Wheat : IV. Analyses of the morphological features of survived tillers from their shoot heights

Abstract

In this study, two experiments were carried out to examine how the tillers survived and adapted morphologically to competition in the wheat (Triticum aestivum L.) plant population. In the first experiment, the heights (highest leaf blade height and stem length) of main stem and tillers were measured from tiller emergence to mid-maturity. It was found that, compared with the heights of main stems, the relative heights of the tillers, especially those which appeared from the leaf axils of higher positions and orders, decreased quickly after elongation of the main stems. In the second experiment, firstly, the heights of smallest tillers (ST) survived in local plant groups (about 30-40 plants), and the local shoot densities surrounding the ST were measured. A positive relationship was found between the local densities of shoots and the heights of ST. Then, analysis of the relationships between the shoot heights and the morphological features showed that, as the shoot heights decreased, the morphological features of shoots changed in the direction favorable to light competition, i.e. the specific leaf area, and the ratios of stem length to stem weight and leaf blade weight (of the uppermost 3 leaves) to stem weight inceased. In ST, these changes were closely related to the stem length differences of the main stems and their ST. These results showed that the tiller's survival was affeted not only by the competition in the plant population but also the morphological changes adapted to the competition.