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Diurnal and seasonal variation in the carbon isotope composition of leaf dark‐respired CO 2 in velvet mesquite ( Prosopis velutina )
Author(s) -
SUN WEI,
RESCO VÍCTOR,
WILLIAMS DAVID G.
Publication year - 2009
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.02006.x
Subject(s) - shrub , perennial plant , isotopes of carbon , photosynthesis , diurnal temperature variation , vapour pressure deficit , daytime , respiration , botany , biology , zoology , ecology , transpiration , atmospheric sciences , total organic carbon , geology
We evaluated diurnal and seasonal patterns of carbon isotope composition of leaf dark‐respired CO 2 ( δ 13 C l ) in the C 3 perennial shrub velvet mesquite ( Prosopis velutina ) across flood plain and upland savanna ecosystems in the south‐western USA. δ 13 C l of darkened leaves increased to maximum values late during daytime periods and declined gradually over night‐time periods to minimum values at pre‐dawn. The magnitude of the diurnal shift in δ 13 C l was strongly influenced by seasonal and habitat‐related differences in soil water availability and leaf surface vapour pressure deficit. δ 13 C l and the cumulative flux‐weighted δ 13 C value of photosynthates were positively correlated, suggesting that progressive 13 C enrichment of the CO 2 evolved by darkened leaves during the daytime mainly resulted from short‐term changes in photosynthetic 13 C discrimination and associated shifts in the δ 13 C signature of primary respiratory substrates. The 13 C enrichment of dark‐respired CO 2 relative to photosynthates across habitats and seasons was 4 to 6‰ at the end of the daytime period (1800 h), but progressively declined to 0‰ by pre‐dawn (0300 h). The origin of night‐time and daytime variations in δ 13 C l is discussed in terms of the carbon source(s) feeding respiration and the drought‐induced changes in carbon metabolism.