Wheat Response to CO2 Enrichment: Growth and CO2 Exchanges at Two Plant Densities |
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Authors: | CLOUX, H. C. DU ANDRE, M. DAGUENET, A. MASSIMINO, J. |
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Abstract: | Du Cloux, H. C, André, M., Daguenet, A. and Massinuno,J. 1987. Wheat response to CO2 enrichment: Growth and CO2 exchangesat two plant densities.J. exp. Bot. 38: 14211431. The vegetative growth of wheat (Triticum aestivum L., var. Capitole)was followed for almost 40 d after germination in controlledconditions. Four different treatments were carried out by combiningtwo air concentrations of CO2, either normal (330 mm3 dm 3)or doubled (660 mm3 dm 3) with two plant densities, either 200plants m 2 or 40 plants m 2. Throughout the experiment the CO2gas exchanges of each canopy were measured 24 h d1. These provideda continuous growth curve for each treatment, which were comparedwith dry weights. After a small stimulation at the start (first13 d), no further effect of CO2 enrichment was observed on relativegrowth rate (RGR). However, RGR was stimulated throughout theexperiment when plotted as a function of biomass. The finalstimulation ol dry weight at 660 mm3 dm 3 CO2 was a factor of1·45 at high density and 1·50 at low density,contrary to other studies, no diminution of this CO2 effecton dry weight was observed over time. Nevertheless, at low density,a transient additional enhancement of biomass (up to 1·70)was obtained at a leaf area index (LAI) below 1. This effectwas attributed to a different build up of the gain of carbonin the case of an isolated plant or a closed canopy. In theformer, the stimulation of leaf area and the net assimilationrate are both involved; in the latter the enhancement becomesindependent of the effect on leaf area because the canopy photosynthesisper unit ground area as a function of LAI reaches a plateau. Key words: Triticum aestuum, L. var. Capitole, Vegetative growth, Canopy |
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