Seasonal Leaf Dimorphism in a Semi-Deciduous Mediterranean Shrub - Ecophysiological Comparisons between Winter and Summer Leaves (Journal article)

Kyparissis, A./ Manetas, Y.

Morphological and physiological properties of winter and summer leaves were examined in the drought semi-deciduous shrub Phlomis fruticosa L. Xerothermic adaptations include a reduction in transpiring surface during summer through both shedding of winter leaves and a significantly lower mean leaf area for the remaining foliage. Leaf specific mass and reflectance are considerably higher in summer leaves. Diffusive resistance to water vapour is higher during summer, associated with low photosynthetic rates. Maximum photosynthesis occurs during the first hours of the day, when evaporative demand is still low. Chlorophylls on a leaf area basis are less in summer leaves but total carotenoids remain relatively unchanged, indicating a decrease in light harvesting but maintainance of photo-protective capacity. Temperature response curves of photosynthesis at saturating light show a 10-degrees-C shift of the optimum temperature from winter to summer. Extensive leaf rolling during summer depends directly on relative water content. It results in a partial self-shading of the upper surface, while the highly reflective lower surface of the leaf is exposed to die direct sun light. This helps the leaf to avoid overheating during the high irradiance and low precipitation Mediterranean summer.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών και Τεχνολογιών. Τμήμα Βιολογικών Εφαρμογών και Τεχνολογιών
Keywords: drought adaptation,leaf dimorphism,leaf rolling,mediterranean climate,morphology,phlomis-fruticosa,photosynthesis,photosynthetic pigments,photosynthetic membranes,water relations,carotenoids,communities,california
ISSN: 1146-609X
Link: <Go to ISI>://A1993LQ91300003
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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