Liu et al. conducted a meta-analysis to test the hypothesis that shade-induced increases in specific-leaf-area (SLA) indicate an adaptive plant response to optimizing light capture.
They conclude that species with greater SLA phenotypic plasticity were less able to maintain biomass under shade. Some of the plastic changes that are frequently thought to be adaptive may simply reflect passive responses to the environment, or occur as by-products of adaptive plastic responses in other traits.
Liu, Y., Dawson, W., Prati, D., Haeuser, E., Feng, Y., & van Kleunen, M. (2016). Does greater specific leaf area plasticity help plants to maintain a high performance when shaded? Annals of Botany, 118(7), 1329–1336. https://doi.org/10.1093/aob/mcw180