Leaf colour polymorphisms: a balance between plant defence and photosynthesis

Abstract

Summary 1.Whether plants use leaf colour to deter herbivores remains controversial. The warning signal hypothesis predicts that red pigmentation is adaptive by reducing herbivory; plants with predominantly red foliage should have higher fitness than those with green leaves. Despite many discussions, this prediction has rarely been tested, and alternative, non-exclusive hypotheses cannot be ruled out. 2.We have exploited leaf colour polymorphism in Pseudowintera colorata to test the warning signal hypothesis and to address possible alternative explanations.3. Consistent with warning signals, redder foliage contained higher concentrations of polygodial, a sesquiterpene dialdehyde with strong antifeedant properties, and incurred less herbivory than green leaves. Redder plants hosted 22% fewer lepidopteran leafroller larvae than neighbouring green plants. 4.However, contrary to the predictions of the hypothesis, there were no differences in fitness parameters between red and green plants. Overall leaf canopy colour was not a significant predictor of the number of seeds per fruit or of mean seed weight. This may be explained by differences in photosynthesis: green P. colorata leaves had 47% higher maximum CO 2 assimilation rates than matched red leaves from neighbouring plants. 5.These results indicate that the benefits of deterring insect herbivores by signalling may be balanced by the higher photosynthetic rate of non-signalling plants. A balance between signalling and photosynthesis is a novel mechanism for the maintenance of leaf colour polymorphisms in nature.6. Synthesis. Anthocyanin pigments may simultaneously serve multiple functions within leaves, and individuals of the same plant species may use different strategies to cope with insect herbivores. Therefore, investigations into the role of these pigments in plant-insect interactions need to consider plant physiology and the diversity of plant defence mechanisms.

Cryptic coloration of Macaranga bancana seedlings: A unique strategy for a pioneer species

“…A more recent study by Chen and Huang, 24 suggests that through phylogenetic analysis, young red leaves have less mechanical protection (in the form of enhanced cuticle, epidermis and trichomes) compared to the green young leaves. Menzies et al 25 demonstrated that the red leaves of the Pseudowintera colorata, has a higher concentration of antifeedant chemical components, incurring less herbivory damage and reduced leaf eating infestation from insects. Hughes and Lev-Yadun 26 discusses the numerous potential ecological and physiological of having red colored leaf margin.…”

Can Anthocyanins be Part of the Metal Homeostasis Network in Plant?

“…In view of the chemical structure of anthocyanins and their histological localization, different protective functions have been hypothesized even though, concerning plant protection against abiotic stress, photoprotection from high light and UV-B (Agati et al, 2007;Tattini et al, 2014) and ROS scavenging ability are the most widely postulated as stress reliever (Gould et al, 2002;Kytridis and Manetas, 2006). On the other hand, defence against herbivores and attraction of pollinators (or preys in carnivorous plants) are the most proposed functions for anthocyanins in terms of relationships with biotic factors (Gould et al, 2009;Hughes and Lev-Yadun, 2015;Menzies et al, 2015). Despite the impossibility to find an universal role for these flavonoids, what in many cases anthocyanic species have in common is the up-regulation of the biosynthesis of those compounds as a cross response to different environmental constrains such as high light, UV-B waveband, drought, high temperatures, ozone, bacterial and fungal infections, wounding, herbivores, herbicides and many other pollutants (i.e., heavy metals) (for review see Landi et al, 2015).…”

Digital photography provides a fast, reliable, and noninvasive method to estimate anthocyanin pigment concentration in reproductive and vegetative plant tissues

“…Variation in floral anthocyanin content or pattering may be under selection by pollinators (Ortiz-Barrientos, 2013;Sletvold, Trunschke, Smit, Verbeek, & Ågren, 2016) or nonpollinators alike (Narbona, Wang, Ortiz, Arista, & Imbert, 2017;Strauss & Cacho, 2013;Strauss & Whittall, 2006). Similarly, the accumulation of anthocyanins in vegetative organs or tissues such as leaves, stems, or pedicels is also influenced by direct or indirect selection of biotic and abiotic factors (Cooney, Schaefer, Logan, Cox, & Gould, 2015;Gould et al, 2010;Menzies et al, 2016). In order to estimate the fitness consequences of such anthocyanin variation (e.g., Del Valle et al, 2015;Sletvold et al, 2016), one must employ an efficient, noninvasive method such as digital photography.…”

“…In reproductive organs, anthocyanins help attract pollinators or seed dispersers, whereas in vegetative organs, they provide protection against environmental stressors such as UV-B radiation, excess light, cold, drought, salinity, pathogens, and/or herbivores (Landi et al, 2015;Lee & Gould, 2002;Schaefer & Ruxton, 2011). Variation in floral and vegetative anthocyanin concentrations within and among populations is common and often adaptive (e.g., Del Valle, Buide, Casimiro-Soriguer, Whittall, & Narbona, 2015;Menzies et al, 2016). Therefore, it is undeniable that the quantification of anthocyanins has become fundamental in understanding many aspects of plant evolutionary ecology (Ortiz-Barrientos, 2013;Sobel & Streisfeld, 2013).…”