© 1997 Heron Publishing—Victoria, Canada
Seasonal courses of CO2 exchange and carbon balance in fruits of Cinnamomum camphora
Kazuharu Ogawa (1) and Yoshinori Takano (1, 2)
1. Section of Forest Ecophysiology, School of Agricultural Sciences, Nagoya University, Chikusa-Ku, Nagoya 464-01, Japan / 2. Department of Forestry, Fukuoka Pref., Fukuoka 807, Japan / Received August 21, 1995
Summary
Carbon dioxide exchange in fruits of Cinnamomum camphora Sieb. was followed over a growing season from July to December 1992. Dark respiration was exponentially related to temperature,
with a Q10 value near 2. Light dependence of photosynthetic CO2 refixation, i.e., the ratio of gross photosynthesis to dark respiration, was approximated by a hyperbolic function. Seasonal
variation in maximum CO2 refixation capacity ranged between 52 and 174%, reaching a maximum in early August. Daily photosynthetic CO2 refixation ranged between 17 and 51% over the growth period. We evaluated seasonal variation in translocation rate to the
fruit on the basis of the seasonal rates of gross photosynthesis, dark respiration and increase in fruit dry weight, and used
the results to develop a simple carbon flow model of fruit development. Seasonal changes in translocation rate paralleled
those in fruit growth rate, with two peaks during the periods before and after September. Seed formation took place in the
period between the two peaks. The relationship between fruit growth rate and translocation rate was approximated by a linear
function. The carbon flow model estimated that, over the reproductive period, the amount of assimilate translocated to each
fruit was 377.2 mg dry weight, of which 58.5% was accounted for by weight growth and 41.5% was consumed by net respiration.
Carbon dioxide refixation accounted for 22.9% of the carbon balance of the fruit.
Keywords:
carbon flow balance, fruit development, photosynthetic CO2 refixation, translocation.
