(18(1):36-48)A STUDY ON THE EFFECT OF ROOTSTOCKS ON TIME OF FLOWER-BUD DIFFERENTIATION OF PONKAN.

提早柑桔果實成熟期為目的，觀察酸桔、廣東檸檬及枳殼等不同砧木椪柑之生理的花芽分化時期並鏡檢形態的花芽分化時期及其發達過程。結果如下： (1)不拘採用何種砧木，11月上旬以前環狀剝皮者翌春之着花數均特多。可見11月上旬前後為椪柑之生理的花芽分化時期。 (2)椪柑之大部份花芽於12月中旬至2月上旬之間分化，而以1月中、下旬為最盛期。三砧木種類中枳殼砧稍較早，酸桔砧為最遲。 (3)萼片之初生突起依葉序之順序而形成。廣東檬及枳殼砧在2月上旬完成萼片期，酸桔砧延至2月下旬完成。 (4)花瓣期，雄蕊期以廣東檬、枳殼、酸桔砧之順序開始，但完成時期均集中於3月間。 (5)花器依枳殼、廣東檬、酸桔砧之順序完成，但三砧間之差異僅為10日前後。 In order to force the fruit ripening earlier, trees of Ponkan (Citrus reticulata, Blanco) grafted on to the Sunki (C. Sunki, Sakurai), Rangpur lime (C. limonia, Osbeck), and Trifoliate orange (Poncirus Trifoliata, Raf.) were examined. Results of the observation for the time of flower-buds differentiation and their development are as follows: 1) The number of flower blooming in the next Spring on the shoot which was girdled before the first part of November had more flower clusters, whatever the rootstock was used. Obviously this is just the time before the physiological differentiation of flower-bud of the Ponkan trees. 2) In morphological observation, most of the flower-buds of Ponkan trees began to differentiate from the middle part of December to the first part of February, but they were prevailing in the middle and late parts of January. Among the three rootstocks used, Trifoliate oranges were earlier than others and Sunki was the latest. 3) The occurring sequence of the primordial calyx of the Ponkan trees was just like the leaf arrangements. They differentiated on the first part of February on both of the Trifoliate orange and Rangpur lime rootstocks, and late part of the same month on Sunki rootstocks. 4) Most of the petals, stamens had fully developed on March. Trees on Rangpur lime were earlier, followed by those on Trifoliate orange and Sunki. 5) For the pistils development, there were only ten days difference between the roots- tocks used. Trees on Trifoliate orange were earlier than Rangpur lime, followed by those on Sunki