Studies on Carbon and Nitrogen Metabolism in Papaya (Carica papaya L.) Leaves of Different Developmental Stages

• Main Authors: Jya-Yaw Liou, 劉家堯
• Other Authors: Song-Iuan Liaw
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/40426289048590359557

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.