Life history and photosynthetic type both affect the economics of leaf physiological function. Annual plants have lower tissue densities and resource use efficiencies than perennials, while C4 photosynthesis, facilitated in grasses by specific changes in leaf anatomy, improves photosynthetic efficiency and water use efficiency, especially in hot climates. Does C4 photosynthesis affect functional trait contrasts between annual and perennial species? We measured 26 traits and characterised niche descriptors for 42 grasses from subtropical China. Differences in the majority of traits were explained by life history. The ranges of annual species (particularly C4 annuals) extended to regions with greater temperature seasonality and lower precipitation, and annuals had less negative turgor loss points, higher specific leaf areas, and lower water use efficiencies, stomatal conductances and leaf areas per stem area than perennials. Photosynthetic type largely affected leaf physiology as expected but interacted with life history in determining specific traits. Leaf hydraulic conductance was intermediate in perennials, highest in C4-annuals, and lowest in C3-annuals. Densities of stomata and stem vessels were similar across C3-perennials and C4 species, but stomatal densities were lower and stem vessel densities higher in C3-annuals. Phylogenetic principal component analysis confirmed that in this subtropical environment life history is the predominant axis separating species, and annuals and perennials were more different within C3 than C4 grasses. The interplay between life history and photosynthetic type may be an overlooked factor in shaping the physiological ecology of grasses.
This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Journal of Experimental Botany following peer review. The definitive publisher-authenticated version Hui Liu, Samuel H Taylor, Qiuyuan Xu, Yixue Lin, Hao Hou, Guilin Wu, Qing Ye, Life history is a key factor explaining functional trait diversity among subtropical grasses, and its influence differs between C3 and C4 species, Journal of Experimental Botany, Volume 70, Issue 5, 15 February 2019, Pages 1567–1580 is available online at: https://academic.oup.com/jxb/article/70/5/1567/5314016