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Pre‐dawn stomatal opening does not substantially enhance early‐morning photosynthesis in H elianthus annuus
Author(s) -
AUCHINCLOSS LISA,
EASLON HSIEN M.,
LEVINE DIEDRE,
DONOVAN LISA,
RICHARDS JAMES H.
Publication year - 2014
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/pce.12241
Subject(s) - morning , stomatal conductance , photosynthesis , horticulture , shoot , helianthus annuus , botany , chemistry , biology , sunflower
Most C 3 plant species have partially open stomata during the night especially in the 3–5 h before dawn. This pre‐dawn stomatal opening has been hypothesized to enhance early‐morning photosynthesis ( A ) by reducing diffusion limitations to CO 2 at dawn. We tested this hypothesis in cultivated H elianthus annuus using whole‐shoot gas exchange, leaf level gas exchange and modelling approaches. One hour pre‐dawn low‐humidity treatments were used to reduce pre‐dawn stomatal conductance ( g ). At the whole‐shoot level, a difference of pre‐dawn g (0.40 versus 0.17 mol m −2 s −1 ) did not significantly affect A during the first hour after dawn. Shorter term effects were investigated with leaf level gas exchange measurements and a difference of pre‐dawn g (0.10 versus 0.04 mol m −2 s −1 ) affected g and A for only 5 min after dawn. The potential effects of a wider range of stomatal apertures were explored with an empirical model of the relationship between A and intercellular CO 2 concentration during the half‐hour after dawn. Modelling results demonstrated that even extremely low pre‐dawn stomatal conductance values have only a minimal effect on early‐morning A for a few minutes after dawn. Thus, we found no evidence that pre‐dawn stomatal opening enhances A .