AbstractAcacia aulacocarpa and Eucalyptus tetrodonta were grown in chambers in which the C02 concentration was either ambient (350 µmol mol-1), or enriched (700 µmol mol-1). The micro-climate (temperature, VPD and PPFD) of the C02 tents was not significantly different from that of outside, though one of the tents was cooler than the other three.
The Acacias were subjected to drought for one week, then re-watered for 4 days, and assimilation measured as a function of increasing LAVPD. Plants had become pot bound, affecting the results, but there was a trend for plants which had been subjected to a period of drought to have a lower assimilation rate. Measurement of dry weight showed that growth in enriched C02 had increased biomass accumulation. Droughted plants had a slightly lower biomass in both C02 treatments.
Eucalyptus tetrodonta were subjected to one of 4 nutrient treatments (+N+P, +N-P, -N+P and -N-P), and chlorophyll fluorescence, assimilation rate, stomatal conductance and internal C02 concentration measured. Some plants were bought into the lab. and assimilation was measured as a function of changing internal C02 concentration. Foliar concentrations of chlorophyll, soluble protein, nitrogen, phosphorus, potassium, magnesium, manganese and calcium were measured. Growth in enriched C02 was found to have enhanced assimilation rate in the early part of the experiment, and plants in high C02 had greater water-use efficiency. Plants in enriched C02 and fertilized with nitrogen (nutrient treatments 1 and 2) had higher assimilation rate than plants in enriched C02 not fertilized with nitrogen. A/Ci analysis revealed that carboxylation efficiency was reduced in high C02, and at high C02 the assimilation rate was limited by an undetermined biochemical factor. Foliar soluble protein concentration was not significantly different between C02 treatments. Foliar nutrient levels were lower in high C02 , but biomass and assimilation had increased, indicating that growth in enriched C02 had resulted in the plants becoming more nutrient-use efficient.
|Date of Award||1994|