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Yellowing and photosynthetic decline of barley primary leaves in response to atmospheric CO2 enrichment
Author(s) -
Sicher Richard C.
Publication year - 1998
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1998.1030206.x
Subject(s) - photosynthesis , hordeum vulgare , photosystem ii , stomatal conductance , chlorosis , chlorophyll fluorescence , chlorophyll , chemistry , horticulture , botany , biology , poaceae
The photosynthetic response of barley ( Hordeum vulgare L. cv. Brant) primary leaves was studied as a function of chlorosis induced by CO 2 enrichment. Leaf yellowing, measured as changes of chlorophyll a and b , was more extensive in controlled environments at elevated (680 ± 17 µl l −1 ) than at ambient (380 ± 21 µl l −1 ) CO 2 . Stomatal conductance of primary leaves was decreased by growth in elevated CO 2 between 11 and 18 days after sowing (DAS) when measured at both 380 and 680 µl l −1 CO 2 . Internal leaf CO 2 concentration (C i ) was also lower for elevated‐ compared to ambient‐CO 2 ‐grown primary leaves between 11 and 14 DAS. Results suggest that non‐stomatal factors were responsible for the decreased photosynthetic rates of elevated‐ compared to ambient‐CO 2 ‐grown primary leaves 18 DAS. Various photochemical measurements, including quantum absorptance (α), minimal (F 0 ), maximal (F m ), and variable (F v ) chlorophyll fluorescence, as well as the F v /F m ratio, were significantly decreased 18 DAS in the elevated‐ compared to ambient‐CO 2 treatment. Photochemical (qP) and nonphotochemical (qN) chlorophyll fluorescence quenching coefficients of 18‐day‐old primary leaves did not differ between CO 2 treatments. Photosynthetic electron transport rates of photosystem II were slightly lower for elevated‐ compared to ambient‐CO 2 ‐grown primary leaves 18 DAS. Concentrations of α‐amino N (i.e. free amino acids) in barley primary leaves were increased by CO 2 enrichment 10 DAS, but subsequently, α‐amino N decreased in association with photosynthetic decline. Total acid protease activity was greater in elevated‐ than in ambient‐CO 2 ‐grown leaves 18 DAS. The above findings suggest that photoinhibition and premature senescence were factors in the CO 2 ‐dependent yellowing of barley primary leaves.