DOI: 10.5061/dryad.xwdbrv1b1
title: C4 photosynthesis and the economic spectra of leaf and root traits independently influence growth rates in grasses

description: Photosynthetic pathway is an important cause of growth rate variation
 between species, such that the enhanced carbon uptake of C4 species leads
 to faster growth than their C3 counterparts. Leaf traits that promote
 rapid resource acquisition may further enhance the growth capacity of C4
 species. However, how root economic traits interact with leaf traits, and
 the different growth strategies adopted by plants with C3 and C4
 photosynthetic pathways is unclear. Plant economic traits could interact
 with, or act independently of, photosynthetic pathway in influencing
 growth rate, or C3 and C4 species could segregate out along a common
 growth rate-trait relationship. We measured leaf and root traits on 100+
 grass species grown from seeds in a controlled, common environment to
 compare with relative growth rates (RGR) during the initial phase of rapid
 growth, controlling for phylogeny and allometric effects. Photosynthetic
 pathway acts independently to leaf and root functional traits in causing
 fast growth. Using C4 photosynthesis, plants can achieve faster growth
 than their C3 counterparts (by an average 0.04 g g-1 day-1) for a given
 suite of functional trait values, with lower investments of leaf and root
 nitrogen. Leaf and root traits had an additive effect on RGR, with plants
 achieving fast growth by possessing resource-acquisitive leaf traits (high
 specific leaf area and low leaf dry matter content) or root traits (high
 specific root length and area, and low root diameter), but having both
 leads to an even faster growth rate (by up to 0.06 g g-1 day-1). C4
 photosynthesis can provide a greater relative increase in RGR for plants
 with a ‘slow’ ecological strategy than in those with fast growth. However,
 aboveground and belowground strategies are not coordinated, so that
 species can have any combination of ‘slow’ or ‘fast’ leaf and root traits.
 Synthesis: C4 photosynthesis increases growth rate for a given combination
 of economic traits, and significantly alters plant nitrogen economy in the
 leaves and roots. However, leaf and root economic traits act independently
 to further enhance growth. The fast growth of C4 grasses promotes a
 competitive advantage under hot, sunny conditions.
description: Datasets leaf_root_trait_average_data.csv =
 Average leaf and root functional trait data
 leaf_root_trait_sizestandardised_data.csv = Leaf and root
 functional traits predicted at a common reference size (the 60th
 percentile for total dry mass across all species and harvests:
 0.044g) Explanation of abbreviations/code names used
 in column headings phylo.name = species name
 avg.RGR = average RGR (g g<sup>-1</sup>
 day<sup>-1</sup>) SLA = ln specific leaf
 area (cm<sup>2</sup>g<sup>-1</sup>)
 LDMC = log leaf dry matter content (%) SRA =
 ln specific root area (cm<sup>2</sup>
 g<sup>-1</sup>) SRL = ln specific root
 length (cm g<sup>-1</sup>) N = log Nitrogen
 concentration (%) C = log Carbon concentration
 (%) root.avg.diam.mm = ln average root diameter
 (mm) PC1/PC2 = principal component analysis axis 1 or
 2 A = minimum mass; one of the four parameters in the
 logistic growth model B = asymptotic or maximum
 mass xmid = or t0 -  time when a plant is midway
 between A and B; one of the four parameters in the logistic growth
 model scal = or k - a growth parameter; one of the four
 parameters in the logistic growth model .sc.60 (column
 name suffix) = trait value predicted at a common reference size (the 60th
 percentile for total dry mass across all species and harvests:
 0.044g)