Evolution of stomatal responsiveness to CO2 and optimization of water-use efficiency among land plants
Brodribb, TJ and McAdam, SAM and Jordan, GJ and Field, TS, Evolution of stomatal responsiveness to CO2 and optimization of water-use efficiency among land plants, New Phytologist, 183, (3) pp. 839-847. ISSN 0028-646X (2009) [Refereed Article]
The stomata of angiosperms respond to changes in ambient atmospheric concentrations
of CO2 (Ca) in ways that appear to optimize water-use efficiency. It is
unknown where in the history of land plants this important stomatal control
mechanism evolved. Here, we test the hypothesis that major clades of plants have
distinct stomatal sensitivities to Ca reflecting a relatively recent evolution of water-use
optimization in derived angiosperms.
Responses of stomatal conductance (gs) to step changes between elevated,
ambient and low Ca (600, 380 and 100 ์mol mol−1, respectively) were compared in
a phylogenetically and ecologically diverse range of higher angiosperms, conifers,
ferns and lycopods.
All species responded to low Ca by increasing gs but only angiosperm stomata
demonstrated a significant closing response when Ca was elevated to 600 ์mol mol−1.
As a result, angiosperms showed significantly greater increases in water-use
efficiency under elevated Ca than the other lineages.
The data suggest that the angiosperms have mechanisms for detecting and
responding to increases in Ca that are absent from earlier diverging lineages, and
these mechanisms impart a greater capacity to optimize water-use efficiency.