Petiole length and biomass investment in support modify light interception efficiency in dense poplar plantations

Abstract

Leaf architecture, stand leaf area index and canopy light interception were studied in 13 poplar clones growing in a second rotation of a coppice plantation, to determine the role of leaf architectural attributes on canopy light-harvesting efficiency and to assess biomass investment in leaf support tissue. Stand leaf area index (L) varied from 2.89 to 6.99, but L was only weakly associated with canopy transmittance (TC). The weak relationship between TC and L was a result of a higher degree of foliage aggregation at larger values of L, leading to lower light-interception efficiency in stands with greater total leaf area. We observed a strong increase in leaf aggregation and a decrease in light-harvesting efficiency with decreasing mean leaf petiole length (PL) but not with leaf size, possibly because, in cordate or deltoid poplar leaves, most of the leaf area is located close to the petiole attachment to the lamina. Although PL was the key leaf characteristic of light-harvesting efficiency, clones with longer petioles had larger biomass investments in petioles, and there was a negative relationship between PL and L, demonstrating that enhanced light harvesting may lead to an overall decline in photosynthesizing leaf surface. Upper-canopy leaves were generally larger and had greater dry mass (MA) and nitrogen per unit area (NA) than lower-canopy leaves. Canopy plasticity in MA and NA was higher in clones with higher foliar biomass investment in midrib, and lower in clones with relatively longer petioles. These relationships suggest that there is a trade-off between photosynthetic plasticity and biomass investment in support, and also that high light-harvesting efficiency may be associated with lower photosynthetic plasticity. Our results demonstrate important clonal differences in leaf aggregation that are linked to leaf structure and biomass allocation patterns within the leaf.

Variability in Populus leaf anatomy and morphology in relation to canopy position, biomass production, and varietal taxon

“…Casella and Ceulemans in 2002 [7] have shown for the same plantation that irradiance could vary from 22 mol of PAR per m 2 morphology: upper canopy leaves are generally longer and larger than lower canopy leaves [1,7,28,51]. Larger top canopy leaves generally take advantage of the higher irradiance by exposing a larger surface to sun.…”

“…SLA is known to be very sensitive to changes in irradiance, and scales negatively with light [1,3,26,[48][49][50][51]. In contrast, the study of Marron et al [40] reported that SLA was mostly dependent on leaf developmental stage (mature vs. expanding leaves).…”

“…Changes in the anatomy and physiology of plant organs in response to environmental stimuli are well documented in poplar [22,35,40,45,46]. Light affects leaf characteristics such as leaf morphology [1,7,48,49,51], leaf anatomy, and stomatal conductance and density [52,62]. The relevance of the use of leaf traits as determinants of biomass production as well as for taxonomic applications is therefore strongly dependent on the growth conditions of the concerned plant material.…”

The architecture of New Zealand's divaricate shrubs in relation to light adaptation

“…Studies of isolated leading shoots of other broad-leaved woody species support this argument (Falster & Westoby 2003). However, within-shoot self-shading of this type may be functionally similar to "clumping" of leaves on shoots in gymnosperms (Oker-Blom et al 1989;Cescatti & Zorer 2003) and poplar (Niinemets et al 2004b), which increases light penetration deep in the crown compared with randomly distributed foliage and may be beneficial when photosynthesis is considered at whole-crown scale.…”

Variations in Leaf Morphological Traits of Quercus guyavifolia (Fagaceae) were Mainly Influenced by Water and Ultraviolet Irradiation at High Elevations on the Qinghai-Tibet Plateau, China

“…For example, the lower temperatures found at higher elevations can restrict the extension of leaves and reduce their size (Magnani and Borghetti, 1995). Stronger solar radiation at higher elevations may lead to lower leaf dry matter, smaller overall sizes, and shorter petioles (Niinemets et al, 2004;Pan et al, 2009). Greater radiation can also promote transpiration, although its effect may be buffered in smaller, shorter leaves (Givnish, 1987;.…”