Stomatal conductance patterns of Equisetum giganteum stems in response to environmental factors in South America

Abstract

As the most basal monilophytes, eusporangiate ferns can provide key insights into the origins of plant physiological adaptations. The genus Equisetum, the most morphologically and physiologically unusual genus of eusporangiate ferns, has a stomatal apparatus that is unique among all plants. Patterns of stomatal diffusive conductance (g w ) were measured in the giant horsetail, Equisetum giganteum L. in southern South America. Maximum g w values (<200 mmol·m −2 ·s −1 ) were low in comparison with typical angiosperm leaves, but were in the range measured in other pteridophytes. The range of measured g w was similar in contrasting environments of the Atacama Desert and northwestern Argentina. Stems in shade had a significantly lower g w than those in light. Developing stems had a higher average g w than mature stems. Stomatal conductance was higher for upper stem internodes than for middle internodes. Late-morning g w was primarily related to stem diameter, stem surface temperature, and interactions among these factors and vapor pressure deficit (VPD), light, elevation, and groundwater salinity. Equisetum giganteum likely has a passive system of stomatal regulation depending on overall stem turgor and red light. The stomatal conductance of patterns of this species exhibited a diurnal pattern typical of other pteridophytes, despite its unusual structure.Résumé : En tant que monilophytes les plus élémentaires, les eusporanges peuvent fournir des informations approfondies sur les origines des adaptations physiologiques des végétaux. Le genre Equisetum, le genre d'eusporanges le plus inhabituel sur les plans morphologique et physiologique, possède un appareil stomatique unique parmi tous les végétaux. Les patrons de conductance diffusive stomatique (g w ) ont été mesurés chez la prêle géante Equisetum giganteum L. dans le sud de l'Amérique du Sud. Les valeurs maximales de g w (<200 mmol·m −2 ·s −1 ) étaient faibles en comparaison avec les feuilles d'angiospermes typiques, mais elles se trouvaient dans les limites mesurées chez les autres ptéridophytes. Les limites de g w mesurées étaient similaires dans les environnements contrastés du désert d'Atacama et du nord-ouest de l'Argentine. Les tiges situées à l'ombre présentaient des valeurs de g w significativement plus faibles que celles situées à la lumière. Les tiges en développement possédaient des valeurs moyennes de g w plus élevées que les tiges matures. La conductance stomatique était plus élevée dans les entrenoeuds supérieurs que dans les entrenoeuds médians. La g w de fin de matinée était principalement reliée au diamètre de la tige, à la température à la surface de la tige et aux interactions entre ces facteurs et le déficit en pression de vapeur (DPV), la lumière, l'altitude et la salinité de la nappe phréatique. Equisetum giganteum possède probablement un système de régulation stomatique passif qui dépend de la turgescence générale de la tige et de la lumière rouge. La conductance stomatique de cette espèce présentait un patron diurne typique des autres ptérid...

Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants

“…This contrasts strongly with the significant increase in foliar ABA levels observed in representative wild-type angiosperm species. While some controversy remains as to whether the stomata of basal vascular land plants respond to ABA (Brodribb and McAdam, 2011;Ruszala et al, 2011), there is an unchallenged compendium of literature based on leaf gas exchange showing highly predictable and ABA-independent responses of fern and lycophyte guard cells to changes in leaf water status (Lösch, 1977(Lösch, , 1979Lösch and Tenhunen, 1981;Brodribb and McAdam, 2011;McAdam andBrodribb, 2012, 2013;Husby et al, 2014;McAdam andBrodribb, 2014, 2015;Martins et al, 2016). Our data support this literature in showing that the biosynthesis of ABA in ferns and lycophytes does not occur over a time frame that is relevant to the stomatal response to VPD.…”

Xylem and stomata, coordinated through time and space

“…Under controlled conditions, as well as in field settings, the stomatal responses to changes in leaf water status in these species can, with high accuracy, be predicted by a simple hydraulic model that assumes guard cell turgor, although higher than epidermal turgor in the light, is directly affected by leaf water potential such that stomatal aperture is directly responsive to biophysical processes of leaf water supply, including leaf hydraulic capacitance, hydraulic conductance and transpiration rate (Brodribb & McAdam ; Husby et al . ; Martins et al . ).…”

Smooth scouringrush (Equisetum laevigatum) control with glyphosate is affected by surfactant choice and application time

“…At Reardan, treatments were applied a month later in the season compared with the other two sites, and the application of glyphosate + OS1 or OS2 only at night resulted in decreased stem densities 1 YAT. These data suggest that OS1 and OS2 resulted in uptake either through the cuticle or more likely through stomata that were either passively open (Husby et al 2014) or open after dark because of the need for stomatal gas exchange (Resco de Dios et al 2013). That we did not see a difference for glyphosate alone between either the day or night applications compared with the nontreated check 1 YAT at any location suggests that neither cuticle nor stomatal uptake was occurring.…”

“…The stomata in Equisetum spp. exhibit a diurnal pattern that depends on stem turgor and red light (Husby et al 2014). It has been reported that Equisetum hyemale L. requires blue light for stomatal opening and photosynthetic CO 2 fixation (Doi et al 2015).…”