Correlation between relative growth rate and specific leaf area requires associations of specific leaf area with nitrogen absorption rate of roots

Abstract

Summary• Close correlations between specific leaf area (SLA) and relative growth rate (RGR) have been reported in many studies. However, theoretically, SLA by itself has small net positive effect on RGR because any increase in SLA inevitably causes a decrease in area-based leaf nitrogen concentration (LNC a ), another RGR component. It was hypothesized that, for a correlation between SLA and RGR, SLA needs to be associated with specific nitrogen absorption rate of roots (SAR), which counteracts the negative effect of SLA on LNC a .• Five trees and six herbs were grown under optimal conditions and relationships between SAR and RGR components were analyzed using a model based on balanced growth hypothesis.• SLA varied 1.9-fold between species. Simulations predicted that, if SAR is not associated with SLA, this variation in SLA would cause a 47% decrease in LNC a along the SLA gradient, leading to a marginal net positive effect on RGR. In reality, SAR was positively related to SLA, showing a 3.9-fold variation, which largely compensated for the negative effect of SLA on LNC a . Consequently, LNC a values were almost constant across species and a positive SLA-RGR relationship was achieved.• These results highlight the importance of leaf-root interactions in understanding interspecific differences in RGR.

A paradox of leaf-trait convergence: why is leaf nitrogen concentration higher in species with higher photosynthetic capacity?

“…Here we assume that these two effects cancel each other. In a data set by Osone et al (2008), the slope of the log-log relationship between photosynthetic capacity and NAR (rate of biomass increment per unit leaf mass) was close to 1 (0.91; r 2 = 0.81), which supports our idea.…”

“…Previous studies have shown that SAR varies greatly among species even when they are grown at the same nutrient availability and that SAR is positively related to A mass in such experiments (Garnier 1991;Poorter et al 1991;Reich et al 1998;Comas et al 2002). Figure 4 shows our experimental results from 11 herbaceous and tree seedlings grown under the same nitrogen condition (data from Osone et al 2008). A mass was correlated with neither leaf-to-plant mass ratio nor leaf-to-plant N ratio, but positively with SAR.…”

“…Similar Fig. 4 The relationship between growth variables and photosynthetic capacity per dry mass (A mass ) in pot-grown seedlings of 11 herbaceous (squares) and tree (circles) species under high nutrient conditions (data derived from Osone et al 2008). N mass , leaf nitrogen concentration per unit dry mass; SAR, nitrogen absorption rate per unit root mass.…”

Autumnal N storage determines the spring growth, N uptake and N internal cycling of young peach trees

“…3), indicating that growth was independent of treatment for these organs not only in late autumn but also in early spring. The existence of growth correlations probably limited the thickening of old axes and root growth once shoot elongation had ceased in autumn (Sone et al 2005;Osone et al 2008). Indeed, root and axis biomass could Table 3 Trees (2012) Fig.…”

Crescimento e eficiência fotossintética de uso do nitrogênio e fósforo em espécies florestais da Amazônia na fase juvenil

“…A diminuição na AFE está frequentemente associada com o aumento no conteúdo de nitrogênio e fósforo por unidade de área foliar (POORTER; EVANS, 1998;REICH et al, 1999;OSONE et al, 2008), devido, em parte, ao maior acúmulo de proteínas fotossintéticas. A eficiência no uso do N foi mais elevada nas espécies com maior área foliar específica, corroborando os resultados de Poorter e Evans (1998) e Reich et al (1998).…”