Shade Tolerance, a Key Plant Feature of Complex Nature and Consequences

Abstract

Light gradients are ubiquitous in nature, so all plants are exposed to some degree of shade during their lifetime. The minimum light required for survival, shade tolerance, is a crucial life-history trait that plays a major role in plant community dynamics. There is consensus on the suites of traits that influence shade tolerance, but debate over the relative importance of traits maximizing photosynthetic carbon gain in low light versus those minimizing losses. Shade tolerance is influenced by plant ontogeny and by numerous biotic and abiotic factors. Although phenotypic plasticity tends to be low in shade-tolerant species (e.g., scant elongation in low light), plasticity for certain traits, particularly for morphological features optimizing light capture, can be high. Understanding differential competitive potentials among co-occurring species mediated by shade tolerance is critical to predict ecosystem responses to global change drivers such as elevated CO2, climate change and the spread of invasive species.

Growth responses and accumulation of soluble sugars in Inga marginata Wild. (Fabaceae) subjected to flooding under contrasting light conditions

“…The comparison between sun and shade plants showed no differences in leaf number, shoot, root, total dry mass and soluble sugar content. Our results, therefore, show similar trends to those of Gonçalves et al (2005), Valladares and Niinemets (2008), Mielke and Schaffer (2010), all of whom observed the largest investment in growth, especially an increase in leaf area and photosynthetic pigments, in plants with similar ecological behavior including those acclimated to shade.…”

“…The classification of a species in different functional groups with respect to their light requirement and acclimation responses to the light environment, help define two distinct groups: species that are considered pioneers or sun species and sun-intolerant species or shade species (Valladares and Niinemets, 2008). The responses to variations in irradiance can occur at the leaf level and involve acclimation of the photosynthetic apparatus (Nobel, 1976;Givnish, 1988) or at the level of entire plant involving changes in growth pattern or biomass allocation (Chazdon and Smith, 1996).…”

Do soil fertilization and forest canopy foliage affect the growth and photosynthesis of Amazonian saplings?

“…Under shade conditions, leaf area per unit leaf dry mass tends to increase to enhance light capture, which ultimately results in thinner leaves (Valladares and Niinemets, 2008). In comparison with thicker leaves, thinner leaves have a lower concentration of photosynthetic proteins per unit leaf area (Hikosaka, 2004).…”

Structural and functional leaf traits of two Gochnatia species from distinct growth forms in a sclerophyll forest site in Southeastern Brazil

“…Higher values of A mass are commonly reported for species growing in lower light environments (Prior et al 2004, Rossatto et al 2009b, which are a indicative that understory species are better competitors for light (Valladares & Niinemets 2008). The differences in A mass were likely to be influenced by the differences in SLA.…”

“…Forest formations, however, have an additional constraint that species should be able to deal with: the great variation in light availability along the vertical continuum through the canopy (Felfili et al 2001). The differences in light conditions may impose adaptation or acclimation of leaves according to the level of light availability: leaves of emergent or canopy trees are exposed to high light intensities and normally are small and thick (Valladares & Niinemets 2008), whereas large and thin leaves of understory species may be a response to limited light conditions (Evans & Poorter 2001;Santiago & Wright 2007). Understanding responses to the local availability of light is fundamental to understanding the adaptation of such species to the forest environment (Hoffmann & Franco 2008).…”