• Journal of Korean Society of Forest Science
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• v.34 no.1
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• pp.63-71
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• 1977

${\times}$Populus albaglandulosa has been needed optimum stand density according to various site and its wood usage. It is assumed that optimum stand density can be estimated by investigating of response of ${\times}$P. albaglandulosa to the light factor of stand. For that reason, the photosynthesis of ${\times}$Populus albaglandulosa grown under the controlled planting density was studied in relation to its leaf age by the aid of the Infrared gas analyzer. Rate of net photosynthesis was smaller in matured leaves than young leaves below $8^{\circ}C$, while, it was larger than young leaves above $8^{\circ}C$. Temperature for the maximum net photosynthesis of young leaves and old leaves was about $30^{\circ}C$ and $25^{\circ}C$ respectively. Saturated light intensity varied slightly as leaf age from 28 Klux to 35 Klux, but net photosynthesis rate in the range of light intensity showed deep differences. Old leaves marked the lowest rate, $1.6\;CO_2\;mg/dm^2/hr$, young leaves marked the medium rate, 1.7 to $2.2\;CO_2\;mg/dm^2/hr$, and matured leaves marked the most efficient photosynthesis, 2.9 to $3.5\;CO_2\;mg/dm^2/hr$. Young leaves of 5 days old had the highest light compensation point, while matured leaves of 35 days-old had the lowest point. Rates of dark respiration in both young leaves and old leaves were higher than that of matured leaves. Trees which were planted at space $80cm{\times}80cm$ showed productive assimilation function over the one-third of height where relative light intensity is 35%.