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Is partitioning of dry weight and leaf area within Dactylis glomerata affected by N and CO2 enrichment?

Harmens, H., Stirling, C.M., Marshall, C., Farrar, J.F.
Annals of botany 2000 v.86 no.4 pp. 833-839
Dactylis glomerata, leaf area, dry matter partitioning, nitrogen, nutrient availability, ontogeny, hydroponics, nitrates, roots, leaf area index, age, carbon dioxide
We examined changes in dry weight and leaf area within Dactylis glomerata L. plants using allometric analysis to determine whether observed patterns were truly affected by [CO2] and N supply or merely reflect ontogenetic drift. Plants were grown hydroponically at four concentrations of (Formula) in controlled environment cabinets at ambient (360 μl l−1) or elevated (680 μl l−1) atmospheric [CO2]. Both CO2and N enrichment stimulated net dry matter production. Allometric analyses revealed that [CO2] did not affect partitioning of dry matter between shoot and root at high N supply. However, at low N supply there was a transient increase in dry matter partitioning into the shoot at elevated compared to ambient [CO2] during early stages of growth, which is inconsistent with predictions based on optimal partitioning theory. In contrast, dry matter partitioning was affected by N supply throughout ontogeny, such that at low N supply dry matter was preferentially allocated to roots, which is in agreement with optimal partitioning theory. Independent of N supply, atmospheric CO2enrichment resulted in a reduction in leaf area ratio (LAR), solely due to a decrease in specific leaf area (SLA), when plants of the same age were compared. However, [CO2] did not affect allometric coefficients relating dry weight and leaf area, and effects of elevated [CO2] on LAR and SLA were the result of an early, transient stimulation of whole plant and leaf dry weight, compared to leaf area production. We conclude that elevated [CO2], in contrast to N supply, changes allocation patterns only transiently during early stages of growth, if at all.