APPLICATION OF C2 3A CHAMBERS : GROWTH AND ALLOMETRY

ISHS Acta Horticulturae 440: International Symposium on Plant Production in Closed Ecosystems

APPLICATION OF C₂ 3A CHAMBERS : GROWTH AND ALLOMETRY

Author:	M. André
Keywords:	CO₂ balance, growth curves, relative growth rate, Triticum aestivum, wheat
Abstract: A continuous and precise measurement of growth rate, expressed in carbon biomass, was allowed from experiments in Closed Chambers Automated in Artificial Atmosphere (C₂ 3A System). Curves were generally better fitted by a function power like w =a (t-t_o)^b, with b close to 3. Such a function is represented by a straight line in log-log scales, suggesting relationship with allometry properties. A model of carbon investment is proposed, leading to explicit the formula: w=a (t-t_o)^b = n ^-n NARⁿ k (t - t_o)ⁿ with NAR=Net Assimilation Rate. Allometry properties are represented by S=k ^n-1, the relation between the area S and , the capacity of storage of carbon assimilated by unit of S; =SLA LWR, with SLA=Specific Leaf Area and LWR=Leaf Weight Ratio. The role of NAR is discussed, the formula suggesting the effect provoked by a difference of NAR (for instance between sun and shade plants) on growth curves. Properties of such a formula are discussed and illustrated from experiments on wheat. The systematic decrease of the relative growth rate, as l/t, imposed by the relationship of allometry does not fit with the concept of exponential growth. The use of RGR, as a criterion of treatment effects on plant growth, are re-examined from the example of treatments giving a growth stimulation without any change of RGR.
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