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Reduced photorespiration and increased energy‐use efficiency in young CO 2 ‐enriched sorghum leaves
Author(s) -
Cousins Asaph B.,
Adam Neal R.,
Wall Gerard W.,
Kimball Bruce A.,
Pinter Paul J.,
Leavitt Steven W.,
LaMorte Robert L.,
Matthias Allan D.,
Ottman Michael J.,
Thompson Thomas L.,
Webber Andrew N.
Publication year - 2001
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.2001.00112.x
Subject(s) - photorespiration , photosynthesis , photosystem ii , chlorophyll fluorescence , c4 photosynthesis , carbon fixation , carbon dioxide , photosynthetic efficiency , botany , biology , chemistry , horticulture , ecology
Summary• To determine the response of C 4 plants to elevated CO 2 it is necessary to establish whether young leaves have a fully developed C 4 photosynthetic apparatus, and whether photosynthesis in these leaves is responsive to elevated CO 2 .• The effect of free‐air CO 2 enrichment (FACE) on the photosynthetic development of the C 4 crop Sorghum bicolor was monitored. Simultaneous measurements of chlorophyll a fluorescence and carbon assimilation were made to determine energy utilization, quantum yields of carbon fixation (φCO 2 ) and photosystem II (φPSII), as well as photorespiration.• Assimilation in the second leaf of FACE plants was 37% higher than in control plants and lower apparent rates of photorespiration at growth CO 2 concentrations were exhibited. In these leaves, φPSII : φCO 2 was high at low atmospheric CO 2 concentration (Ca) due to overcycling of the C 4 pump and increased leakiness. As Ca increased, φPSII : φCO 2 decreased as a greater proportion of energy derived from linear electron transfer was used by the C 3 cycle.• The stimulation of C 4 photosynthesis at elevated Ca in young leaves was partially due to suppressed photorespiration. Additionally, elevated Ca enhanced energy‐use efficiency in young leaves, possibly by decreasing CO 2 leakage from bundle sheath cells, and by decreasing overcycling of the C 4 pump.