Quantitative analysis of carbon balance in the reproductive organs and leaves of <Emphasis Type="Italic">Cinnamomum camphora</Emphasis> (L.) Presl |
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Authors: | Shunsuke Imai Kazuharu Ogawa |
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Institution: | (1) Laboratory of Forest Ecology and Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan;(2) Present address: Aichi Prefectural Federation of Forest Cooperatives, Marunouchi, Naka-ku, Nagoya 460-0020, Japan |
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Abstract: | We investigated seasonal changes in dry mass and CO2 exchange rate in fruit and leaves of the evergreen tree Cinnamomum camphora with the aim of quantitatively determining the translocation balance between the two organs. The fruit dry mass growth peaked
in both August and October: the first increase was due to fruit pulp development and the second to seed development. Fruit
respiration also increased with the rapid increase in fruit dry mass. Therefore, the carbohydrates required for fruit development
showed two peaks during the reproductive period. Fruit photosynthesis was relatively high in early August, when fruit potentially
re-fixed 75% of respired CO2, indicating that fruit photosynthesis contributed 15–35% of the carbon requirement for fruit respiration. Current-year leaves
completed their growth in June when fruit growth began. Current-year leaves translocated carbohydrates at a rate of approximately
10–25 mg dry weight (dw) leaf−1 day−1 into other organs throughout the entire fruit growth period. This rate of translocation from current-year leaves was much
higher than the amount of carbohydrate required for reproduction (ca. 3 mg dw fruit−1 day−1). Given the carbon balance between fruit and current-year leaves, carbohydrates for reproduction were produced within the
current-year fruit-bearing shoots. C. camphora would be adaptive for steadily supplying enough amount of carbohydrate to the fruits, as there was little competition for
carbohydrates between the two organs. As assimilates by leaves are used for processes such as reproduction and the formation
of new shoots, photosynthesis by reproductive organs is considered to be important to compensate for reproductive cost. |
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Keywords: | CO2 re-fixation Cinnamomum camphora (L ) Presl Fruit and leaf photosynthesis Fruit and leaf respiration Reproductive cost Translocation |
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