PLANT PHYSIOLOGY , Vol 115, Issue 1 199-203, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Growth and N Allocation in Rice Plants under CO2 Enrichment
A. Makino, M. Harada, T. Sato, H. Nakano and T. Mae
Department of Applied Biological Chemistry, Faculty of Agriculture, Tohoku University, Tsutsumidori-Amamiyamachi, Sendai 981, Japan
The effects of CO2 enrichment on growth and N allocation of rice (Oryza
sativa L.) were examined. The plants were grown hydroponically in growth
chambers with a 14-h photoperiod (1000 [mu]mol quanta m-2 s-1) and a
day/night temperature of 25/20[deg]C. From the 28th to 70th d after
germination, the plants were exposed to two CO2 partial pressures, namely
36 and 100 Pa. The CO2 enrichment increased the final biomass, but this was
caused by a stimulation of the growth rate during the first week of the
exposure to elevated CO2 partial pressures. The disappearance of the
initial stimulation of the growth rate was associated with a decreased leaf
area ratio. Furthermore, CO2 enrichment decreased the investment of N in
the leaf blades, whereas the N allocation into the leaf sheaths and roots
increased. Thus, the decrease in leaf N content by CO2 enrichment was not
due to dilution of N caused by a relative increase in the plant biomass but
was due to the change in N allocation at the whole-plant level. We conclude
that the growth responses of rice to CO2 enrichment are mainly controlled
by leaf area expansion and N allocation into leaf blades at the whole-plant
level.
