Analytical Studies on the Process of Growth and Production of Mat Rush (Juncus decipiens Nakai) : II. Relationship between hill size at transplanting and the long stem yield

[摘要] The relationship between hill size (number of seedling stems per hill) at transplanting and yield of the long stems was studied with two mat rush cultivars, i.e. Asanagi (tiller type) and Shimomasuda-zairai (elongation type). Two plots, i.e. a large hill size plot and a small hill size plot, were arranged for each cultivar. The large hill and the small hill consisted of 10 stems-10 buds and 3 stems-3 buds, respectively. The process of tillering, stem elongation and dry matter production were analysed. The results are summarized as follows : 1. In both cultivars, number of stems per hill, dry weight per hill and stem surface area index (SAI) in the large hill size plot gradually increased from the early stage of the growing season to the harvest time. However, in the small hill size plot, these growth parameters began to increase about one month later than the large hill size plot, and markedly increased from the middle of April to the middle of June, then reached a maximum about 20 days before the harvest time. 2. In Asanagi, net assimilation rate (NAR) in the large hill size plot gradually decreased from the beginning of March to the harvest time, while NAR in the small hill size plot began to increase rapidly in the beginning of March, then reached the higher level than that of the large hill size plot, but decreased faster than in the large hill size plot, and consequently NAR in this plot was lower than that of the large hill size plot after the beginning of July. Crop growth rate (CGR) in the small hill size plot was lower than that of the large hill size plot before the beginning of May and after the beginning of July. The differences in the changes of these parameters between the large and the small hill size plot were almost similar in both cultivars. 3. Tillering behavior of both plots in Asanagi was similar. However, in Shimomasuda-zairai, tillering behavior was qualitatively different, because the 3rd nodal tillering as compared with the 2nd nodal tillering was weaker in the small hill size plos than in the large hill size plot. 4. The long stems of the small hill size plot mainly consisted of the tillers having 1 or 2 lower order positions and being shorter than those of the large hill size plot. The long stem yield of the small hill size plot was 28 percent lower than that of the large hill size plot. 5. In Asanagi, the tillers on the same order position elongated in the similar behavior, and the tillers on the 12th to the 17th position in the main tillering group had the characteristic to elongate faster and to become the longer stems. The elongation rate and the length of the tillers emerged after the latter part of May were closely related to the level of CGR after the end of June. 6. These results would show the reasons why much attention has to be paid to the degree of growth at the tillering stage of the long stems in the cultivation of mat rush.

[学科分类] 农业科学（综合）