Response of photosynthesis, stomatal conductance and water use efficiency to elevated CO2 and nutrient supply in acclimated seedlings of Phaseolus vulgaris L.
1992), , (
P. G. Jarvis
– – Annals of Botany 70,257–264. –
Plants of Phaseolus vulgaris L were grown from seed in open-top growth chambers at present day (350 μmol mol−1) and double the present day (700 μmol mol−1) atmospheric CO2 concentration with either low (L, without additional nutrient solution) or relatively high (H, with additional nutrient solution) nutrient supply
Measurements of assimilation rate, stomatal conductance and water use efficiency were started 17 d after sowing on each fully expanded, primary leaf of three plants per treatment Measurements were made in external CO2 concentrations (C2) of 200, 350, 450, 550 and 700 μmol mol−1 and related to both Ca and to C1, the mean intercellular space CO2 concentration Fully adjusted, steady state measurements were made after approx 2 h equilibration at each CO2concentration
The rate of CO2 assimilation by leaves increased and stomatal conductance decreased similarly over the range of Ca or C1 in all four CO2and nutrient supply treatments but both assimilation rate and stomatal conductance were higher in the high nutrient supply treatment than in the low nutrient treatment.
The relation between assimilation rate or stomatal conductance and C1 was not significantly different amongst plants grown in present-day or elevated CO2 concentration in either nutrient supply treatment, i. e. there was no evidence of down regulation of photosynthesis or stomatal response Increase in CO2 concentration from 350 to 700 μmol mol−1 doubled water use efficiency of individual leaves in the high nutrient supply treatment and tripled water use efficiency in the low nutrient supply treatment
The results support the hypothesis that acclimation phenomena result from unbalanced growth that occurs after the seed reserves are exhausted, when the supply of resources becomes growth limiting.