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

Abstract

Background and Aims It is frequently assumed that phenotypic plasticity can be very advantageous for plants, because it may increase environmental tolerance (fitness homeostasis). This should, however, only hold for plastic responses that are adaptive, i.e. increase fitness. Numerous studies have shown shade-induced increases in specific leaf area (SLA), and there is wide consensus that this plastic response optimizes light capture and thus has to be adaptive. However, it has rarely been tested whether this is really the case.Methods In order to identify whether SLA plasticity does contribute to the maintenance of high biomass of plant species under shaded conditions, a meta-analytical approach was employed. The data set included 280 species and 467 individual studies from 32 publications and two unpublished experiments.Key Results Plants increased their SLA by 55Á4 % on average when shaded, while they decreased their biomass by 59Á9 %. Species with a high SLA under high-light control conditions showed a significantly greater ability to maintain biomass production under shade overall. However, in contrast to the expectation of a positive relationship between SLA plasticity and maintenance of plant biomass, the results indicated that species with greater SLA plasticity were less able to maintain biomass under shade.Conclusions Although a high SLA per se contributes to biomass homeostasis, there was no evidence that plasticity in SLA contributes to this. Therefore, it is argued that some of the plastic changes that are frequently thought to be adaptive might simply reflect passive responses to the environment, or result as by-products of adaptive plastic responses in other traits.

Jump‐starting coastal wetland restoration: a comparison of marsh and mangrove foundation species

“…Avicennia was able to grow at all elevations with varying survival, but differences between individuals only manifested themselves in SLA. At the lowest elevation, SLA was significantly greater, indicating a lack of water stress (Knight & Ackerly ), but also may be indicative of competitive shading from the surrounding Spartina canopy (Liu et al ). Tree height and biomass increased over time and did not differ by elevation but did show some differences in growth morphology by 18 months.…”

Responses of common and rare aliens and natives to nutrient availability and fluctuations

“…Instead, we tested how the change in biomass across two nutrient conditions (i.e. log-response ratios of biomass) relates to plasticity in the trait of interest across the same two nutrient conditions, using the 29 species as replicates (see Liu et al 2016a). These analyses revealed some significant relationships between plastic responses of some of the root traits and the plant performance response to nutrients (see Methods S5).…”

Genotype by environment interactions for the shade avoidance syndrome in the plantAntirrhinum majus, the snapdragon

“…In a situation where light may become, or is already, scarce, stem elongation through increased distance between nodes and/or stem height is expected to allow plants that are not shade tolerant to outgrow competitors. An increase in SLA in the shade, while technically not a shade avoidance strategy, is a functional response that has often been observed (Lewandowska and Jarvis, 1977; Dong, 1995; Evans and Poorter, 2001; van Kleunen et al , 2011; Liu et al , 2016), and is expected to improve the physiological performance of plants in a light-limited environment.…”