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Water relations traits of C4 grasses depend on phylogenetic lineage, photosynthetic pathway, and habitat water availability.

ABSTRACT: The repeated evolution of C4 photosynthesis in independent lineages has resulted in distinct biogeographical distributions in different phylogenetic lineages and the variants of C4 photosynthesis. However, most previous studies have only considered C3/C4 differences without considering phylogeny, C4 subtype, or habitat characteristics. We hypothesized that independent lineages of C4 grasses have structural and physiological traits that adapt them to environments with differing water availability. We measured 40 traits of 33 species from two major C4 grass lineages in a common glasshouse environment. Chloridoideae species were shorter, with narrower and longer leaves, smaller but denser stomata, and faster curling leaves than Panicoideae species, but overall differences in leaf hydraulic and gas exchange traits between the two lineages were weak. Chloridoideae species had two different ways to reach higher drought resistance potential than Panicoideae; NAD-ME species used water saving, whereas PCK species used osmotic adjustment. These patterns could be explained by the interactions of lineage×C4 subtype and lineage×habitat water availability in affected traits. Specifically, phylogeny tended to have a stronger influence on structural traits, and C4 subtype had more important effects on physiological traits. Although hydraulic traits did not differ consistently between lineages, they showed strong covariation and relationships with leaf structure. Thus, phylogenetic lineage, photosynthetic pathway, and adaptation to habitat water availability act together to influence the leaf water relations traits of C4 grasses. This work expands our understanding of ecophysiology in major C4 grass lineages, with implications for explaining their regional and global distributions in relation to climate.

SUBMITTER: Liu H

PROVIDER: S-EPMC4321540 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

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Water relations traits of C4 grasses depend on phylogenetic lineage, photosynthetic pathway, and habitat water availability.

Liu Hui H Osborne Colin P CP

Journal of experimental botany 20141212 3

The repeated evolution of C4 photosynthesis in independent lineages has resulted in distinct biogeographical distributions in different phylogenetic lineages and the variants of C4 photosynthesis. However, most previous studies have only considered C3/C4 differences without considering phylogeny, C4 subtype, or habitat characteristics. We hypothesized that independent lineages of C4 grasses have structural and physiological traits that adapt them to environments with differing water availability ...[more]

PMID: 25504656

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Project description:Background and aimsThe success of C4 plants lies in their ability to attain greater efficiencies of light, water and nitrogen use under high temperature, providing an advantage in arid, hot environments. However, C4 grasses are not necessarily less sensitive to drought than C3 grasses and are proposed to respond with greater metabolic limitations, while the C3 response is predominantly stomatal. The aims of this study were to compare the drought and recovery responses of co-occurring C3 and C4 NADP-ME grasses from the subfamily Panicoideae and to determine stomatal and metabolic contributions to the observed response.MethodsSix species of locally co-occurring grasses, C3) species Alloteropsis semialata subsp. eckloniana, Panicum aequinerve and Panicum ecklonii, and C4 (NADP-ME) species Heteropogon contortus, Themeda triandra and Tristachya leucothrix, were established in pots then subjected to a controlled drought followed by re-watering. Water potentials, leaf gas exchange and the response of photosynthetic rate to internal CO2 concentrations were determined on selected occasions during the drought and re-watering treatments and compared between species and photosynthetic types.Key resultsLeaves of C4 species of grasses maintained their photosynthetic advantage until water deficits became severe, but lost their water-use advantage even under conditions of mild drought. Declining C4 photosynthesis with water deficit was mainly a consequence of metabolic limitations to CO2 assimilation, whereas, in the C3 species, stomatal limitations had a prevailing role in the drought-induced decrease in photosynthesis. The drought-sensitive metabolism of the C4 plants could explain the observed slower recovery of photosynthesis on re-watering, in comparison with C3 plants which recovered a greater proportion of photosynthesis through increased stomatal conductance.ConclusionsWithin the Panicoid grasses, C4 (NADP-ME) species are metabolically more sensitive to drought than C3 species and recover more slowly from drought.

Dataset Information

Water relations traits of C4 grasses depend on phylogenetic lineage, photosynthetic pathway, and habitat water availability.

Publications

Water relations traits of C4 grasses depend on phylogenetic lineage, photosynthetic pathway, and habitat water availability.

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