Root Contribution in Controlling Vegetative and Reproductive Growth in Citrus Growing

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For 3 years, our experiments were carried out to evaluate the root contribution in controlling vegetative and reproductive growth of citrus trees. Inoue and Kataoka clarified that low temperatures below 25℃ are necessary to initiate flower bud initiation under plastic green house growing conditions. Yamashita pointed out kinetin has a significant role for root growth. Hasegawa noticed that throughout the period from October to February carbohydrate accumulation was active in the roots of 'Tosabuntan' pomelo. Ishii and Kadoya carried out experiments from the view pint of Low Input Sustainable Agriculture in citrus growing. The results are as follows ; (1) Infection of VAM fungi was high in gramineous and leguminous weeds. (2) Sod culture system with those plants was effective to increase infection percentage of VAM fungi in citrus roots. (3) Prolonged use of phosphorous fertilizer resulting in over 50ppm of residual PO43- in the soil caused low VAM infection in the roots. (4) 25% MeOH eluates of citrus juice pomace extracts contain stimulatory substances for VAM fungi. Further the application of the 25%MeOH eluates to the soil is very effective in stimulating VAM fungi activity. (5) Three kinds of compounds were isolated from the eluates. Two of them are identified as hesperidin and narirutin. Those cocompounds stimulated the hyphal growth of Gigaspora margarita. (6) It can be stressed that VAM fungi proliferation in the soil will be the primary importance for the promotion of Low Input Sustainable Agriculutre.