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    Masataka Yamashita, Kurume Branch, National Research Institute of Vegetables, Ornamental Plants and Tea. 14041 Beppu, Makurazaki-shi, Kagoshima, 898 Japan

    It has been pointed out that root systems play important roles to shoot growth, yield and quality. But, there are a few researches on roots or root systems because the influences of roots on the yield and quality are indirect, the observation of roots requires much labour and time and direct managements to roots are difficult. The roots, however, support the nutuient and water uptake, and biosynthesis of some hormons and useful chemical components. Therefore, the development and functions of root systems could greatly control the shoot growth, yield and quality.
        On basis of this conception, the rejuvination of the tea plants by the root pruning technique has been studied. It has been experientially known that the technique was affected by many factors such as time, intensity and frequency of pruning, manuaring, variaties, plant age, plant vigour and relationship with shoot pruning. In this study, the relationship between the root regenration, and the time and intensity of the root pruning were discussed.
                     MATERIALS AND METHODS

          Experiment I: The influences of the pruning times on root regeneration were examined using 4- to 5-year-old plants from 1982 to 1984. Many, late June, late August. late September and late November. The rate of lignified and white roots removed by the pruning were 35% and 71% in fresh weight on the average, respectively. The growth and root regeneration after the treatments were investigated in the next early way. The root regenerating potential (RRP) was estimated by 3 indecies of (a): the ratio of white root weight to lignified root weight within the basal range, (b): the number of white roots a lignified root that reproduced white roots around the cross section and (c): the weight (mg) a white root reproduced around the cross section. The reserve carbohydrate content of roots was analyzed at each late time from May to September.
          Experiment II: The influences of the pruning intensities on root regeneration were examined using 4-year-old plants from 1982 to 1983. The root prunings were carried out at 5 levels for both sides of each plant as shown in Fig. 2. The rate of roots lost by the treatments ranged from 76% in the intensity I (serverest) to 23% in the intensity V (lightest) as shown in table I. The growth and root regeneration after treatments were gated similarly to the experiment I.

          Experiment I: As shown in table 2, the root pruning severely restricted both the shoot and root growth in no relation with the time. Influences of the late November pruning were lightest on shoot growth, while severest on root growth. This was probably because of the reduction of the shoot growth. This was probably because of the reduction of the shoot growth due to lowering of the air temperature and the restriction of the root growth by lowering of the soil temperature. The root growth in the August pruning was inferior next to that in the November pruning. When the roots were divided into the lignified roots and white roots, the 2 sorts of roots indicated different reactions to the root pruning, respectively. As shown in Fig. 3, the amount of the lignified roots in each pruning time was about 40% less than that in the control. The rate almost coincided with the rate of roots removed by the pruning. This presented that the lignified roots were difficult to recover after the pruning. While, as shown in Fig. 4. the white roots markedly increased increased by the root pruning from the lat May to the late September. Consequently, the weight of the white roots in these 4 pruning times were 1.5 to 2.5 times as much as that in the control. This suggested that the new roots could be rapidly regenerated after the prunings under a favorate condition. But, the root regeneration in the late August pruning deteriorated somewhat as compared with the regeneration in the other three times. It was considered that a high temperature and aridity in the late August worked as factors inhibiting the active root regeneration
    The root regeneration was activated not only around cross sections RRP was evaluated.    













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