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Abstract Detail


Ecophysiology

Taylor, Samuel [1], Rees, Mark [1], Woodward, Ian [1], Ripley, Brad [2], Osborne, Colin [1].

Phylogeny, physiology and ecology: the roles of C4 photosynthesis and diversity in the grasses.

The C4 syndrome is a remarkable example of convergent evolution that has arisen in at least eight lineages of grasses. The pathway improves photosynthetic resource use efficiency under a range of conditions, particularly those common in tropical regions with low annual rainfall. Strong expectations about the effects of C4 photosynthesis on physiology, combined with the diversity of ecological types observed among grasses, present a unique opportunity to investigate trait diversity and trait convergence in a phylogenetic context. Here, we ask: 1) Which traits differ consistently between grass lineages exhibiting C4 and C3 photosynthesis? 2) Which traits differ among grass lineages independently of photosynthetic pathway? In a screening experiment comparing 34 grass species, including six C4 clades and three groups of C3 sister taxa, we tested hypotheses about the key physiological traits expected to differ between C3 and C4 photosynthetic types. Results supported the expectations of lower stomatal conductance, and greater water and nitrogen use efficiency in C4 than C3 species. However, differences in photosynthetic rates and leaf nitrogen concentration were smaller than expected. Our results also highlighted evidence of phylogenetic conservatism in leaf traits such as SLA, which interacted with the effects of C4 photosynthesis. A second screening experiment compared the physiological responses to drought in a phylogenetically structured sample of 13 C3 and C4 grass species. Results showed that the differences in stomatal conductance observed between C3 and C4 species under mesic conditions were eliminated under drought. Data were also consistent with the hypothesis that metabolic limitation of photosynthesis under drought is more pronounced in C4 than C3 species. Finally, we found further evidence of phylogenetic conservatism in leaf traits, especially SLA. Accounting for the phylogenetic diversity of C4 grass species has provided new insights into the impacts of this photosynthetic pathway on plant function.

Broader Impacts:


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1 - University of Sheffield, Department of Animal and Plant Sciences, Sheffield, S10 2TN, UK
2 - Rhodes University, Botany Department, Grahamstown, 6139, South Africa

Keywords:
C4 photosynthesis
grasses
Poaceae
eco-physiological traits
gas exchange
Screening
phylogeny.

Presentation Type: Oral Paper:Papers for Topics
Session: 30
Location: 551B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 9:00 AM
Number: 30003
Abstract ID:364


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