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Title: Graphical partitioning of seedling phenotypic plasticity of seven cool-season grass species subjected to two watering frequencies

item ZHENG, WEI - Xinjiang Agricultural University
item Monaco, Thomas
item Jones, Thomas
item Peel, Michael

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2019
Publication Date: 6/14/2019
Citation: Zheng, W., Monaco, T.A., Jones, T.A., Peel, M. 2019. Graphical partitioning of seedling phenotypic plasticity of seven cool-season grass species subjected to two watering frequencies. Journal of Arid Environments. 170.

Interpretive Summary: Plant species may respond to environmental stress by changing shoot or root biomass in ways that confer species-specific adaptation to that stress. We found that some cool-season grass species increased both shoot and root growth in response to increased water (growth plasticity), while others increased shoot growth while decreasing root growth (allocation plasticity). These responses were displayed on a two-dimensional graph that allowed the quantification of growth and allocation plasticities. Characterizing species for such plastic (non-genetic) responses may illuminate their strategies for stress avoidance, tolerance, or resistance. Such information may lead to a more judicious use of species in low-moisture environments based on their anticipated plastic responses, as well as comparison of genotypes within species, leading to plant breeding opportunities.

Technical Abstract: Successful establishment of grass seedlings depends on their ability to adapt to changes in soil moisture, and this ability may be related to phenotypic plasticity. As a case-study of plasticity to water availability, we measured 45-d seedling root and shoot dry-mass of seven cool-season grass species grown under two watering-frequency (WF) regimes in a glasshouse. To depict plasticity, we developed a graphic method with three salient features. First, we partitioned plasticity into two components, 1) 1:1 growth plasticity and 2) plasticity for root:shoot allocation. Second, we calculated 1) total dry-mass to measure growth plasticity and 2) root mass fraction (RMF) to measure allocation plasticity. Third, we plotted each species' plastic response to WF on a graph with four axes: 1) shoot dry-mass, 2) root dry-mass, 3) total dry-mass, and 4) RMF. Three species displayed predominately growth plasticity, and four species displayed only allocation plasticity. Growth-plasticity species are opportunistic and can capitalize on additional water, while allocation-plasticity species may increase the probability of their survival by tailoring RMF to reflect current soil-moisture status.