Changes in source-sink relations during development influence photosynthetic acclimation of rice to free air CO2 enrichment (FACE)
Loading...
Date
2002
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Relationships between photosynthetic acclimation and changes in the balance between source-sink supply and demand of carbon l C) and nitrogen (N) were tested using rice (Oryza sativa L cv. Akitakomachi). Plants were field-grown in northern Japan at ambient CO2 partial pressure (P(C02)] or free air CO2 enrichment (FACE; - 26-32 Pa above ambient) with low, medium or high N supplies. Leaf CO2 assimilation rates (A) and biochemical parameters were measured at 32-36 (eighth leaf) and 76-80 (flag leaf) d after transplanting, representing stages with It contrasting balance between C and N supply and demand in sources and sinks. Acclimation due to FACE was pronounced in flag leaves at each N supply. This was not fully accounted for by reductions in leaf N concentrations, because A/N and Vcmax/N were lower in FACE-grown flag leaves. Acclimation did not occur in the eighth leal: andAIN and VcmaxlN was not significantly increased in FACE-grown leaves. Soluble protein/sucrose and amino acid/sucrose concentrations decreased under FACE, whereas sucrose phosphate synthase protein levels increased. At flag leaf stage, there was a discrepancy between the demand and supply of N, which was resolved by enhanced leaf N remobilization, associated with the lower Rubisco concentrations under FACE. In contrast to the early growth stage, enhanced growth of rice plants was accompanied by increased plant N uptake in FACE. We conclude that photosynthetic acclimation in flag leaves occurs under FACE because there is a large demand for N for reproductive development, relative to supply of N from root uptake and remobilization from leaves.
Description
Keywords
Citation
Funct. Plant Biol., 2002, 29, 945-953