Spatial distribution of leaf nitrogen and photosynthetic capacity within the foliage of individual trees: disentangling the effects of local light quality, leaf irradiance, and transpiration

Abstract

There is presently no consensus about the factor(s) driving photosynthetic acclimation and the intra-canopy distribution of leaf characteristics under natural conditions. The impact was tested of local (i) light quality (red/far red ratio), (ii) leaf irradiance (PPFD(i)), and (iii) transpiration rate (E) on total non-structural carbohydrates per leaf area (TNC(a)), TNC-free leaf mass-to-area ratio (LMA), total leaf nitrogen per leaf area (N(a)), photosynthetic capacity (maximum carboxylation rate and light-saturated electron transport rate), and leaf N partitioning between carboxylation and bioenergetics within the foliage of young walnut trees grown outdoors. Light environment (quantity and quality) was controlled by placing individual branches under neutral or green screens during spring growth, and air vapour pressure deficit (VPD) was prescribed and leaf transpiration and photosynthesis measured at branch level by a branch bag technique. Under similar levels of leaf irradiance, low air vapour pressure deficit decreased transpiration rate but did not influence leaf characteristics. Close linear relationships were detected between leaf irradiance and leaf N(a), LMA or photosynthetic capacity, and low R/FR ratio decreased leaf N(a), LMA and photosynthetic capacity. Irradiance and R/FR also influenced the partitioning of leaf nitrogen into carboxylation and electron light transport. Thus, local light level and quality are the major factors driving photosynthetic acclimation and intra-canopy distribution of leaf characteristics, whereas local transpiration rate is of less importance.

Dynamics of Light and Nitrogen Distribution during Grain Filling within Wheat Canopy

“…Changes in the relationship between SLN and PPFD have been related to plant size and N status (Lötscher et al, 2003). There is also some evidence that light quality (in particular the red to far-red ratio) influences N distribution in the canopy (Rousseaux et al, 1999;Frak et al, 2002), but the spectral component of the light gradient is probably less important than the total irradiance component (Pons and de Jong-van Berkel, 2004). It has clearly been demonstrated that accumulation of cytokinins imported through the xylem is involved in the regulation of vertical leaf N distribution (Pons et al, 2001;Boonman et al, 2007).…”

Changes in light quality alter physiological responses of soybean to thiamethoxam

“…Several lines of evidence suggest that in some plant species FR-E light causes reductions in photosynthetic capacity, CO 2 assimilation and nitrogen levels (Frak et al 2002;Boccalandro et al 2009;Cagnola et al 2012). We investigated this in soybean by measuring levels of C and N in shoots and roots and compared the impact of TMX on C and N levels under FR-D and FR-E light.…”

Non-invasive approaches for phenotyping of enhanced performance traits in bean

“…Light intensity and quality change quickly within natural canopies at different time scales exposing single leaf elements to a variable stream of photons (Frak et al 2002;Yamashita et al 2002). Dynamic acclimation of photosynthetic efficiency to these changes in environmental light conditions are still not well understood (Rascher and Nedbal 2006) and novel approaches to measure canopy structure and function simultaneously are urgently needed.…”