• Medientyp: E-Artikel
  • Titel: Diurnal pattern of stomatal conductance in the large-leaved temperate liana Aristolochia macrophylla depends on spatial position within the leaf lamina
  • Beteiligte: Miranda, Tatiana; Ebner, Martin; Traiser, Christopher; Roth-Nebelsick, Anita
  • Erschienen: Oxford University Press, 2013
  • Erschienen in: Annals of Botany
  • Umfang: 905-915
  • Sprache: Englisch
  • DOI: 10.1093/aob/mct061
  • ISSN: 0305-7364; 1095-8290
  • Zusammenfassung: <p>• Background and Aims The large distance between peripheral leaf regions and the petiole in large leaves is expected to cause stronger negative water potentials at the leaf apex and marginal zones compared with more central or basal leaf regions. Leaf zone-specific differences in water supply and/or gas exchange may therefore be anticipated. In this study, an investigation was made to see whether zonal differences in gas exchange regulation can be detected in large leaves. • Methods The diurnal course of stomatal conductance, g s , was monitored at defined lamina zones during two consecutive vegetation periods in the liana Aristolochia macrophylla that has large leaves. Local climate and stem water potential were also monitored to include parameters involved in stomatal response. Additionally, leaf zonal vein densities were measured to assess possible trends in local hydraulic supply. • Key Results It was found that the diurnal pattern of g s depends on the position within a leaf in A. macrophylla. The highest values during the early morning were shown by the apical region, with subsequent decline later in the morning and a further gradual decline towards the evening. The diurnal pattern of g s at the marginal regions was similar to that of the leaf tip but showed a time lag of about 1 h. At the leaf base, the diurnal pattern of g s was similar to that of the margins but with lower maximum g s . At the the leaf centre regions, g s tended to show quite constant moderate values during most of the day. Densities of minor veins were lower at the margin and tip compared with the centre and base. • Conclusions Gas exchange regulation appears to be zone specific in A. macrophylla leaves. It is suggested that the spatial-diurnal pattern of g s expressed by A. macrophylla leaves represents a strategy to prevent leaf zonal water stress and subsequent vein embolism.</p>
  • Beschreibung: <p>• Background and Aims The large distance between peripheral leaf regions and the petiole in large leaves is expected to cause stronger negative water potentials at the leaf apex and marginal zones compared with more central or basal leaf regions. Leaf zone-specific differences in water supply and/or gas exchange may therefore be anticipated. In this study, an investigation was made to see whether zonal differences in gas exchange regulation can be detected in large leaves. • Methods The diurnal course of stomatal conductance, g s , was monitored at defined lamina zones during two consecutive vegetation periods in the liana Aristolochia macrophylla that has large leaves. Local climate and stem water potential were also monitored to include parameters involved in stomatal response. Additionally, leaf zonal vein densities were measured to assess possible trends in local hydraulic supply. • Key Results It was found that the diurnal pattern of g s depends on the position within a leaf in A. macrophylla. The highest values during the early morning were shown by the apical region, with subsequent decline later in the morning and a further gradual decline towards the evening. The diurnal pattern of g s at the marginal regions was similar to that of the leaf tip but showed a time lag of about 1 h. At the leaf base, the diurnal pattern of g s was similar to that of the margins but with lower maximum g s . At the the leaf centre regions, g s tended to show quite constant moderate values during most of the day. Densities of minor veins were lower at the margin and tip compared with the centre and base. • Conclusions Gas exchange regulation appears to be zone specific in A. macrophylla leaves. It is suggested that the spatial-diurnal pattern of g s expressed by A. macrophylla leaves represents a strategy to prevent leaf zonal water stress and subsequent vein embolism.</p>
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