Abstract
It is evident that Rumex obtusifolius invades tame pasture by means of the diffusion and the spread of the seeds produced by wild Rumex obtusifolius around the pasture. Therefore, it is essential for the effective control of Rumex obtusifolius to disturb the reproductive phase or to interrupt the process of the seed maturity. With a view to surveying the possibility of the above control method, it was carried out to evaluate temperature and day-length influences on the heading and the flowering of Rumex obtusifolius, and to determine the time of flowering of various perennial plants growing in the same field in Nasu, Tochigi-pref. The results obtained were as follows ; 1) The heading of the plants growing under 12hr. or shorter day-length was never able to be induced at any day/night temperature regime. These plants remained in the state at the beginning of the reproductive phase until late in June. Under natural and 16hr day-length, however, the heading and the flowering were induced at all the temperature regimes of 30℃/20℃, 20℃/10℃ in the controlled green house, and natural temperature from May to June in field. 2) Under the same long day-length over 12hr., both the heading and the flowering were hastened as temperature regime increased from 20℃/10℃ to 30℃/20℃. On the other hand, at the same temperature regime the heading was hastened as day-length increased over 12hr., but the flowering would scarcely be influenced by day-length. 3) The high temperature regime of 30℃/20℃ resulted in a marked decrease in the period from heading to flowering. From the assessment of the above results, it is apparent that temperature may strongly affect the period from heading to flowering, and consequently hasten the time of flowering. 4) The time of flowering of various perennial plants growing in the same field in Nasu, Tochigi-pref. was determined. The flowering appeared from early June to early July, mostly mid-June. The variance of the time of flowering of the plants more than a year old shows that the flowering may depend not only on day-length and temperature, but also on the endogenous factors.
