Species-Independent Down-Regulation of Leaf Photosynthesis and Respiration in Response to Shading: Evidence from Six Temperate Tree Species

Abstract

The ability to down-regulate leaf maximum net photosynthetic capacity (Amax) and dark respiration rate (Rdark) in response to shading is thought to be an important adaptation of trees to the wide range of light environments that they are exposed to across space and time. A simple, general rule that accurately described this down-regulation would improve carbon cycle models and enhance our understanding of how forest successional diversity is maintained. In this paper, we investigated the light response of Amax and Rdark for saplings of six temperate forest tree species in New Jersey, USA, and formulated a simple model of down-regulation that could be incorporated into carbon cycle models. We found that full-sun values of Amax and Rdark differed significantly among species, but the rate of down-regulation (proportional decrease in Amax or Rdark relative to the full-sun value) in response to shade was not significantly species- or taxon-specific. Shade leaves of sun-grown plants appear to follow the same pattern of down-regulation in response to shade as leaves of shade-grown plants. Given the light level above a leaf and one species-specific number (either the full-sun Amax or full-sun Rdark), we provide a formula that can accurately predict the leaf's Amax and Rdark. We further show that most of the down regulation of per unit area Rdark and Amax is caused by reductions in leaf mass per unit area (LMA): as light decreases, leaves get thinner, while per unit mass Amax and Rdark remain approximately constant.

A photorespiratory bypass increases plant growth and seed yield in biofuel crop Camelina sativa

“…Analysis of whether larger cells in bypass transgenics have a higher number of chloroplasts, whether the chloroplasts are larger in size, and measurements of overall RuBisCO content would be necessary to correlate the anatomical data with increased photosynthesis per unit area in the bypass plants. It also remains to be investigated whether the larger leaves in camelina bypass transgenics shade lower leaves and prevent them from reaching their highest photosynthetic potential in field conditions [ 62 ].…”

Functional Trait Variation Among and Within Species and Plant Functional Types in Mountainous Mediterranean Forests

“…Functional traits such as LMA are known to be sensitive to variation in light availability, with higher irradiance leading to higher LMA (Poorter et al, 2009). Intraspecific LMA variability between sunlit and shaded leaves has been shown for all three PFTs (Wyka et al, 2012;Gratani, 2014) with lower values recorded in shaded leaves and potentially leading to downregulation of gas exchange rates (Chen et al, 2014). In our study, all understory species that had no individual at the sunlit part of the canopy were sampled for trait measurements outside the plot, in sunnier places in order to reduce such environmental effects and enable between species and sites comparisons.…”

Moisture availability mediates the relationship between terrestrial gross primary production and solar‐induced chlorophyll fluorescence: Insights from global‐scale variations

“…This article is protected by copyright. All rights reserved environmental stresses such as droughts (e.g., Huang et al, 2019;Piao et al, 2017;Sun et al, 2015) and shade (e.g., Chen et al, 2014;Gamon & Bond, 2013). A few studies have suggested that stresses increase NPQ but reduce GPP more than SIF, leading to reduced GPP/SIF ratios (Hilker et al, 2008;Gu et al, 2019).…”