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During the development period of muskmelon, the photo-synthetic
rate of the upper leaves decreased apparently. The export of
photoassimilates in upper leaves was reduced and un-able
transported to the fruit sufficiently, and resulted in the slow
growth rate of fruit. Our purpose here is to improve the photo-
synthetic rate in order to increase the content of sucrose in
leaves, to supply sufficient carbon, and to refine the quality
of muskmelon.We used 30 ppm of benzyladenine (BA) to treat the
plant that is 7-day after anthesis. The result indicates that
both leaf area and biomass of the BA-treated plants are much
higher more then the control. Referred to the tissue anatomy,
the leaf thickness of the BA-treated plants increases obviously.
This is because that BA can promote leaf cells to absorb more
water, and as a result, to enlarge the cells. Besides, the
number of the chloroplast also increases suggesting an improved
photosyn-thetic rate.As for carbon metabolism, the sucrose
phosphate synthase (SPS) activity of the BA-treated plant is
higher than that of the control. The activity approaches to the
maximum on the 15th day after BA-treated, but gradually
diminishes until fruit gath-ering indicating that the rate of
sucrose synthesis decreases. However, the content of sucrose in
the BA-treated leaves in-crease evidently. Our result suggests
that sucrose is accumu-lated in the leaves and fails to
transport to the fruits. So, the quality of the fruit reduces.
As to the aspect of sucrose degra-dation, the activity of the
neutral invertase in the BA-treated plant increase and the
content of hexose increase consequently. The increased
concentration of hexose can provide sufficient carbon source for
the leaves to grow.Our conclusion is that plants treated with BA
can avoid leaves from senescence. Is can also increase
photosynthetic rate of the leaves, and furthermore, promote
sucrose accumula-tion in leaves. But it cannot provide abundant
sucrose for de-veloping fruit. And the weight of the fruit
decreases conse-quently. So, if we treated the plant with 30
ppm of BA 7-days after anthesis, we still cannot refine the
quality of fruit. Whether it is a question of the inadequate
treating period is still a doubt and needs further research.
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