Shade tolerance plasticity in response to neutral vs green shade cues in Polygonum species of contrasting ecological breadth

Abstract

Summary• Here we examined species differences in perception and response to two distinct types of shade cue, reduced photosynthetically active radiation (PAR) with and without reduced red : far red ratio (R : FR), in Polygonum persicaria and Polygonum hydropiper , two closely related annuals of contrasting ecological breadth.• We compared plasticity data for light-gathering traits from glasshouse experiments at equivalently reduced PAR under neutral shade (R : FR 1.03) and green shade (R : FR 0.702).• Species shared the ability to distinguish between the two types of shade, as shown by the ability of each to respond differently to neutral vs green shade for one or more traits. However, the species' responses to these cues differed significantly. Polygonum persicaria expressed stronger shade-tolerance responses (increased leaf allocation and leaf area ratio) to reduced PAR alone than to green shade. By contrast, P. hydropiper expressed slightly less plasticity for these traits in neutral than in green shade.• The pronounced plastic response of P. persicaria to neutral shade may contribute to the range of habitats this widespread species can occupy, which includes neutralshade environments such as urban settings.

Divergence among species and populations of Mediterranean pines in biomass allocation of seedlings grown under two watering regimes

“…However, this is the only possible way to isolate genetic effects form treatment effects. Similar approaches are commonly used in common garden provenance studies in and in most plasticity studies [6,16,45].…”

Does greater specific leaf area plasticity help plants to maintain a high performance when shaded?

“…The estimates of effect size of biomass may be affected by whether or not the same genetic plant material is used in both the high-light and shading treatments (Gianoli and Valladares, 2012) and by whether neutral shade (reduced light quantity alone) or canopy shade (reduced light quantity with altered spectral quality) is used (Griffith and Sultan, 2005). However, as in our data set, only six studies used the same genetic material in the different treatments and only three studies used canopy shade in high-light and shade treatments, we did not include these two factors in the main meta-analytical model described above.…”

Ecological consequences of phenotypic plasticity

“…For instance, submerged tadpoles might sense imminent pond drying through changes in temperature or chemical concentration, visual effects of surface proximity, or increased swim contact to induce accelerated metamorphosis [76]. Moreover, plasticity cues can consist of specific aspects of environmental variables, such as the spectral quality of shade treatments [77]. Recognizing these specific factors is crucial because their correlations with particular ecological pressures can vary from one habitat or site to another, shaping the expression and evolution of plasticity in distinct populations [78].…”