| Summary: | 碩士 === 國立中興大學 === 園藝學系 === 85 === Summary
The buds of 'Heng-Shan' pear tree (Pyrus serotina R.) go into
dormancy in September and remain in a state of deep dormancy
from late November to early January. The degree of
dormancy diminish from February and emergces in March in
Taitung prefecture, Taiwan. The total soluble sugar content
of shoots maintained high in late October, then decreased
rapidly during deep dormancy period and thereafter
increased again at budbreak time. The starch content
increased from summer to autumn, and reached the maximum level
in late October , then dropped significantly after
February. Water content , protein nitrogen, and non-
protein nitrogen concentrations of shoots decreased during the
period of deep dormancy and increased when the dormancy
came to an end. Chilling
requirement of single bud cutting of 'Heng-Shan' pear
reached 50% budbreak when shoots was exposed to 0 , 5 and 10℃
for 192 hours. However, in a potted plant test , 50% budbreak
occurred when plants were chilled at 5℃ for 288 hours. The
longer low temperature the shoots or pot plants was
exposed, the shorter time was needed to break buds. Budbreak
was enhanced when insufficiently chilled
shoots or pot plants was treated with 1:4(fertilizer
: water) or 1:8 calcium cyanamide solution. But the
percentage of budbreak could not be able to reach 50% level if
shoots or potted plant were not chilled. The percentage of
budbreak was over 50% when exposed to low temperature(5 or
10℃) for 48 hours together with 1:4 calcium
cyanamide solution. For buds or pot plants not
receiving adequate chilling , the longer the low temperature for
both shoots and pot plants, the better results could be obtained
with calcium cyanamide solution was treated. The ratio of 1:4
calcium cyanamide was found to have more significant effects
on budbreak. Field experiment was showed that induction of
budbreak was least effective when applied in the
middle of December if dormant 'Heng-Shan' pear trees were
sprayed with calcium cyanamide solution(1:8) ,
however, better result could be expected if it was applied
in the middle of January or February. The content of total
soluble sugar increased rapidly and accumulated early in shoots
in the middle February sampling. The optimal time to break
dormancy was in late January in Taitung. Spraying
solution filtering process, in general, did not affect much
in this experiment.
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