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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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