Abstract:
Crop plants are shown to have high photosynthetic rate at elevated C 0 2 concentrations. Experiments were
conducted with an objective to study the influence of elevated C 0 2 concentration and relative humidity
(RH) on seedling growth of Eucalyptus citriodora, Derris indica, Spathodea companulata and Acacia
auriculiformis. A simple cost effective technique was developed and standardised to increase the C 0 2
concentration and RH around the seedlings in a forest nursery. Increase in the C 0 2 concentration to about
700-800 pmol mol'1 during the night and only a few hours during the day increased the biomass of all the
species tested. Growth response to elevated C 0 2and RH was more in Derris and Spathodea than in the other
two species examined. In all the species gas exchange studies showed increased photosynthesis with
instantaneous increase in C 0 2 concentration. High growth in Acacia was associated with better leaf area
development whereas it was due to better photosynthetic efficiency in Eucalyptus. The experiment proved
that the technique can be effectively used to enhance seedling growth in forest
