Stomatal and pavement cell density linked to leaf internal CO2 concentration.
OBJECTIVE
Stomatal density (SD) generally decreases with rising atmospheric CO2 concentration, Ca. However, SD is also affected by light, air humidity and drought, all under systemic signalling from older leaves. This makes our understanding of how Ca controls SD incomplete. This study tested the hypotheses that SD is affected by the internal CO2 concentration of the leaf, Ci, rather than Ca, and that cotyledons, as the first plant assimilation organs, lack the systemic signal.


METHODS
Sunflower (Helianthus annuus), beech (Fagus sylvatica), arabidopsis (Arabidopsis thaliana) and garden cress (Lepidium sativum) were grown under contrasting environmental conditions that affected Ci while Ca was kept constant. The SD, pavement cell density (PCD) and stomatal index (SI) responses to Ci in cotyledons and the first leaves of garden cress were compared. (13)C abundance (δ(13)C) in leaf dry matter was used to estimate the effective Ci during leaf development. The SD was estimated from leaf imprints.


RESULTS
SD correlated negatively with Ci in leaves of all four species and under three different treatments (irradiance, abscisic acid and osmotic stress). PCD in arabidopsis and garden cress responded similarly, so that SI was largely unaffected. However, SD and PCD of cotyledons were insensitive to Ci, indicating an essential role for systemic signalling.


CONCLUSIONS
It is proposed that Ci or a Ci-linked factor plays an important role in modulating SD and PCD during epidermis development and leaf expansion. The absence of a Ci-SD relationship in the cotyledons of garden cress indicates the key role of lower-insertion CO2 assimilation organs in signal perception and its long-distance transport.
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic Biology Centre, Institute of Plant Molecular Biology AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic jsan@umbr.cas.cz.
Jiří
J
Santrůček
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Martina
M
Vráblová
Biology Centre, Institute of Plant Molecular Biology AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Marie
M
Simková
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic Biology Centre, Institute of Plant Molecular Biology AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Marie
M
Hronková
Biology Centre, Institute of Plant Molecular Biology AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Martina
M
Drtinová
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Jiří
J
Květoň
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Daniel
D
Vrábl
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Jiří
J
Kubásek
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Jana
J
Macková
Biology Centre, Institute of Plant Molecular Biology AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Dana
D
Wiesnerová
Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
Jitka
J
Neuwithová
Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany.
Lukas
L
Schreiber
D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D002452:Cell Count; D018548:Cotyledon / Q000187:drug effects / Q000502:physiology; D003681:Dehydration; D004777:Environment; D029964:Fagus / Q000166:cytology / Q000187:drug effects; D006368:Helianthus / Q000166:cytology / Q000187:drug effects; D029686:Lepidium / Q000166:cytology / Q000187:drug effects; D054046:Plant Stomata / Q000166:cytology* / Q000187:drug effects
D002245:Carbon Dioxide
13C discrimination; Arabidopsis thaliana; Fagus sylvatica; Helianthus annuus; Lepidium sativum; Stomatal density; cotyledons; leaf internal CO2; pavement cells; stomata development