| Summary: | 碩士 === 國立中興大學 === 植物學系 === 83 === In this research different developmental stages of papaya
leaves were used to investigate the changes in carbon and
nirogen meta- bolism and their assimulation into the
chloroplast and cytoplasm during the development and senecence
of the leaves.The results revealed that the photosynthetic rate
will increase with the sink-source transition process of the
leaves.At the same time, the activity of Rubisco will also
increase.SPS,the activity of which follows the change in the
amount of sucrose.As expected, as the sucrose builds up the
starch falls off, demonstrating that the SPS functions in
regulating this coordination with SPS acti- vity and the amount
of sucrose.Acid invertase was found to be the most important
enzyme in this sucrose breakdown in papaya leaves. Sucrose
synthetase and neutral invertase, the relation between them and
sucrose amount is much lower than the relationship bet- ween
sucrose and acid invertase. The respiratory rate of the dif-
ferent developmental stages of the papaya leaves is inversely
proportional to the age of the leaves. the level of adenylate
is also found to be in proportion to the respiratory rate. As
the leaves approach old age the amino acid concentration
decreases which possibly causes an increase in the rate of flow
of nitrate into the leaves and therefore the activity of
nitrate reductase also increases.Nitrate reductase peaks in
mature leaves, while in immature and senescent leaves its
activity is low, Glutamine syn- thetase and NADH-GOGAT
(glutamate synthase) activity is compara- tively high in mature
leaves. There is another form of glutamate synthase, Fd-GOGAT
(ferredoxin-GOGAT), whose activity is diffe- rent because it
is regulated by ammonium ions which are released from the
photorespiration in different leaf developmental stages. The
glutamate dehydrogenase NADH- and NADPH-GDH , in the processs
of development of the leaves, deals with glutamate breakdown.
As the activity of these two isozymes is similar.
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