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Is stomatal conductance optimized over both time and space in plant crowns? A field test in grapevine ( V itis vinifera )
Author(s) -
BUCKLEY THOMAS N.,
MARTORELL SEBASTIA,
DIAZESPEJO ANTONIO,
TOMÀS MAGDALENA,
MEDRANO HIPÓLITO
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.12343
Subject(s) - transpiration , stomatal conductance , curvature , conductance , mathematics , vitis vinifera , crown (dentistry) , horticulture , botany , chemistry , photosynthesis , geometry , combinatorics , biology , materials science , composite material
Crown carbon gain is maximized for a given total water loss if stomatal conductance ( g s ) varies such that the marginal carbon product of water (∂ A /∂ E ) remains invariant both over time and among leaves in a plant crown, provided the curvature of assimilation rate ( A ) versus transpiration rate ( E ) is negative. We tested this prediction across distinct crown positions in situ for the first time by parameterizing a biophysical model across 14 positions in four grapevine crowns ( V itis vinifera ), computing optimal patterns of g s and E over a day and comparing these to the observed patterns. Observed water use was higher than optimal for leaves in the crown interior, but lower than optimal in most other positions. Crown carbon gain was 18% lower under measured g s than under optimal g s . Positive curvature occurred in 39.6% of cases due to low boundary layer conductance ( g bw ), and optimal g s was zero in 11% of cases because ∂ A /∂ E was below the target value at all g s . Some conclusions changed if we assumed infinite g bw , but optimal and measured E still diverged systematically in time and space. We conclude that the theory's spatial dimension and assumption of positive curvature require further experimental testing.