Winter leaf reddening in ‘evergreen’ species

Abstract

SummaryLeaf reddening during autumn in senescing, deciduous tree species has received widespread attention from the public and in the scientific literature, whereas leaf reddening in evergreen species during winter remains largely ignored. Winter reddening can be observed in evergreen herbs, shrubs, vines and trees in Mediterranean, temperate, alpine, and arctic regions, and can persist for several months before dissipating with springtime warming. Yet, little is known about the functional significance of this colour change, or why it occurs in some species but not others. Here, the biochemistry, physiology and ecology associated with winter leaf reddening are reviewed, with special focus on its possible adaptive function. Photoprotection is currently the favoured hypothesis for winter reddening, but alternative explanations have scarcely been explored. Intraspecific reddening generally increases with sunlight incidence, and may also accompany photosynthetic inferiority in photosynthetically 'weak' (e.g. low-nitrogen) individuals. Red leaves tend to show symptoms of shade acclimation relative to green, consistent with a photoprotective function. However, winter-red and winter-green species often cohabitate the same high-light environments, and exhibit similar photosynthetic capacities. The factors dictating interspecific winter leaf colouration therefore remain unclear. Additional outstanding questions and future directions are also highlighted, and possible alternative functions of winter reddening discussed.

Related but not alike: not all Hemiptera are attracted to yellow

“…Consequently, the general consensus is that there is little imperative for herbivorous insect to be attracted to red leaves and typically anthocyanin-rich senescing leaves are not utilized by sucking insects (Kennedy et al, 1961;Chittka and Döring, 2007). Although it has attracted much less attention, "red" coloration is also common in young, expanding leaves of many evergreen trees (Chalker-Scott, 2002;Karageorgou and Manetas, 2006;Manetas, 2006;Hughes, 2011) including those in the genus Eucalyptus (Sharma and Crowden, 1974;Thomas and Barber, 1974;Specht and Brouwer, 1975). Since variations in pigment concentrations are often associated with changes in leaf physiology, they should provide cues to psyllids and other insects reliant on visual location and assessment of hosts.…”

Multiple functional roles of anthocyanins in plant-environment interactions

“…Because anthocyanins occur so commonly across disparate vegetative organs, there has been concerted research effort to understand their functional significance, particularly in plants that experience abiotic stressors (Chalker-Scott 1999;Hoch et al, 2001;Steyn et al, 2002;Close and Beadle 2003;Gould, 2004;Manetas, 2006;Gould et al, 2009;Archetti, 2009a;Hughes, 2011;Tonelli et al, 2015). Nonetheless, after well over a century of research and despite a comprehensive knowledge on the regulation of anthocyanin biosynthesis (Winkel, 2006), their functional roles in plant-environment interactions remain highly contested (for a review see Gould et al, 2009).…”

Photosynthetic ecophysiology of evergreen leaves in the woody angiosperms – a review

“…Red leaf coloration is enhanced by solar radiation and is accompanied by the decrease of the chlorophyll a/b ratio, suggesting a shading effect of pigments on the chloroplasts. Although light screening is the favored explanation for the presence of anthocyanins, their role as antioxidants is also possible (Hughes 2011). A variety of other acclimatory metabolic changes have been described, e.g.…”