Response of stomatal numbers to CO₂ and humidity: control by transpiration rate and abscisic acid

Abstract

Summary• The observation that stomatal density (number mm −2 ) on herbarium leaves had decreased over the last century represents clear evidence that plants have responded to anthropogenic increases in CO 2 concentration. The mechanism of the response has proved elusive but here it is shown that density responses to both CO 2 concentration and humidity are correlated with changes in whole-plant transpiration and leaf abscisic acid (ABA) concentration.• The transpiration rate of a range of accessions of Arabidopsis thaliana was manipulated by changing CO 2 concentration, humidity and by exogenous application of ABA. Stomatal density increased with transpiration and leaf ABA concentration.• A common property of signal transduction systems is that they rapidly lose their ability to respond to the co-associated stimulus. Pathways of water movement within the plant are connected and so variations in supply and demand can be signalled throughout the plant directly, modifying stomatal aperture of mature leaves and stomatal density of developing leaves. Furthermore, the system identified here does not conform to the loss of ability to respond.• A putative mechanism is proposed for the control of stomatal density by transpiration rate and leaf ABA concentration.

Phenotypic plasticity of European beech (Fagus sylvatica L.) stomatal features under water deficit assessed in provenance trial

“…Although Holland and Richardson (2009) reported that stomatal density and guard cell length are both sensitive to environmental conditions and that considerable genotypic variation and phenotypic plasticity occurred in these traits, our study showed that differences among provenances in regards to guard cell length were not statistically significant, despite the decrease of L A in dry year for all provenances (Table 2). This is in agreement with the results presented by other authors, who found that stomatal density appears to be relatively plastic compared to stomatal length (Richardson et al 2001) and therefore, potentially adaptive to environmental change (Lake and Woodward 2008). Our study also showed that stomatal density increased with drought, which is consistent with the results obtained in some other plant species (Klooster and Palmer-Young 2004;Fraser et al 2009).…”

“…Fraser et al (2009) also found that reduction of water supply in the field caused an increase in stomatal density, while the range in temperatures of approximately 2.8°C did not have significant effect on stomatal density. Likewise, study of Lake and Woodward (2008) evidenced that number of stomata increased in response to increasing VPD. Similarly, studying an impact of high and low vapor pressure deficit on leaf anatomical traits, Carins Murphy et al (2014) found that high VPD caused reduction of leaf area, whereas the leaf stomatal density increased.…”

Stomatal Responses to Drought Stress and Air Humidity

“…Similar experiments have been preformed with air humidity, increased air humidity results in increased stomatal density (Sciutti and Morini, 1995). The stomatal density has been found to increase in plants with decreased ABA concentrations, which also have increased transpiration (Lake and Woodward, 2008). In Vicia faba drought and salinity stress has been found to increase the stomatal density and stomatal index, facilitating water uptake under water stressed conditions (Gan et al, 2010).…”

“…In Arabidopsis thaliana it has been shown that ABA-deficient and ABA-insensitive mutants responded similarly as wild type plants to changes in humidity (Assmann et al, 2000). Plants developed under low ABA conditions also have higher stomatal density (Lake and Woodward, 2008), indicating that ABA is important in both the development of stomata size and density. ABA application in lower concentrations, applied to plants can reduce transpiration rate and increase the shelf life of Salvia splendens and a number of other ornamentals, by inducing stomatal closure (Pompodakis et al, 2004;Waterland et al, 2010a;Waterland et al, 2010b;Kim and van Iersel, 2011).…”

Functional Analysis of Cellulose and Xyloglucan in the Walls of Stomatal Guard Cells of Arabidopsis

“…In addition, we did not observe phenotypes indicative of compromised water transport, such as wilted leaves, in the cesa3 je5 mutants. Therefore, we propose that cellulose deficiency in cesa3 je5 mutants more directly causes an increase in stomatal aperture, whereas in cesa7 irx3-5 mutants, the smaller stomatal aperture brought about by decreased guard cell size might be due to collapsed xylem and compromised water transport , as fluctuations of supply and demand during water movement across the plant can modulate stomatal development (Lake and Woodward, 2008).…”