PLANT PHYSIOLOGY , Vol 115, Issue 1 15-22, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Accelerated Early Growth of Rice at Elevated CO2 (Is It Related to Developmental Changes in the Shoot Apex?)
D. S. Jitla, G. S. Rogers, S. P. Seneweera, A. S. Basra, R. J. Oldfield and J. P. Conroy
School of Horticulture, University of Western Sydney, Hawkesbury, Locked Bag No. 1, Richmond NSW 2753, Australia (D.S.J., G.S.R.,S.P.S., A.S.B., J.P.C.)
The influence of elevated CO2 on the development of the shoot apex and on
subsequent vegetative growth and grain yield was investigated using rice
(Oryza sativa L. cv Jarrah) grown in flooded soil at either 350 or 700
[mu]L CO2 L-1. At 8 d after planting (DAP), elevated CO2 increased the
height and diameter of the apical dome and lengths of leaf primordia and
tiller buds but had no effect on their numbers. By 16 DAP, there were five
tiller buds in the apex at 700 [mu]L CO2 L-1 compared with only three
tiller buds at 350 [mu]L CO2 L-1. These changes in development of the shoot
apex at high CO2 were forerunners to faster development of the vegetative
shoot at elevated CO2 between 11 and 26 DAP as evidenced by increases in
the relative growth rates of the shoot and tillers. Accelerated development
at high CO2 was responsible for the 42% increase in tiller number at the
maximum tillering stage and the 57% enhancement of grain yield at the final
harvest. The link between high CO2 effects on development during the first
15 DAP and final tiller number and grain yield was demonstrated by delaying
exposure of plants to high CO2 for 15 d. The delay totally inhibited the
tillering response to high CO2, and the increase in grain yield of 20%
arose from a greater number of grains per panicle. Consequently, it can be
concluded that accelerated development in the shoot apex early in
development is crucial for obtaining maximum increases in grain yield at
elevated atmospheric CO2 concentrations.
