Abstract
It was found by the authors10) that if citrus trees were cultivated under the alternate high temperature (day: 25-30°C and night: 15-20°C) during winter season, the differentiation of fibrous tissue in wood was taken place even in winter season.
Two year old Hassaku twigs (Citrus hassaku) which had stem pitting on wood were grafted on sweet lime (Citrus limeettioides) stocks. Ten months later, they were used as materials in the experiments. That is, after dividing them into two sets, one set was cultivated under the alternate high temperature (day: 25-30°C and night: 15-20°C) during winter season (from the beginning of October till the end of April) and another in natural condition of the same winter. As a consequence of the experiments, the formation of new stem pitting was not detected under the alternate high temperature (Fig. 3A1 and A2), but it appeared on wood in natural conditions (Fig. 3B1 and B2).
This observation provided that the stem pitting phenomenon on wood of citrus tree depends on the cambial condition which has been influenced by thermoperiodicity.
