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Stomatal Density

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StomatalPeel

A potentially important seedling trait is stomatal density. Woodward (1987) found that stomatal density and distribution may affect gas exchange and associated relationships with environmental factors such as light, CO2, and water status.

Xu and Zhou (2008) found that stomatal density increased, but the number of stomata per-leaf decreased with water stress, and this change in stomatal density was correlated to changes in specific leaf area water use efficiency in another species of perennial grass.

Stomatal density may therefore be an important adaptive trait for bluebunch wheatgrass in the Great Basin. We aim to fill the knowledge gap surrounding seedling stomatal density in bluebunch wheatgrass to determine whether adaptation to climate exists for this trait.

StomatalPeelZoomStomate Study

Hypothesis & objective:

We hypothesize that stomatal density is a driver of drought tolerance in young bluebunch wheatgrass plants and that the variability in this trait is caused by natural selection and local adaptation. Our objective is to determine the range of variability in stomatal density in populations along an aridity gradient and to tie this trait to selection through climate. Using an exploratory approach, we will measure stomatal densities from young plants (grown from seed-sources along an aridity gradient) and determine their relationship to climate in terms of aridity.

Expected results and interpretations:

We predict that there is a negative correlation between stomatal density and aridity. If this prediction is supported, then there is evidence that natural selection has reduced stomatal density in arid environments as compared to less arid environments. If this prediction is not supported, then we must conclude that stomatal density does not change in relation to aridity.

References:

Woodward, F. I. 1987. “Stomatal Numbers Are Sensitive to Increases in CO2 from Pre-Industrial Levels.” Nature 327 (6123): 617–18. doi:10.1038/327617a0.

Xu, Zhenzhu, and Guangsheng Zhou. 2008. “Responses of Leaf Stomatal Density to Water Status and Its Relationship with Photosynthesis in a Grass.” Journal of Experimental Botany 59 (12): 3317–25. doi:10.1093/jxb/ern185.

 

Research Overview

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Introduction:

Despite the growing number of scientists, federal and state agencies, private citizens, and non-profit organizations working to restore damaged ecosystems in the Great Basin, intact native plant communities continue to decline.CrookedRiver3small

The shift away from native-perennial to invasive annual-grass dominated systems has reduced biodiversity, increased wildfire severity and frequency, and has expedited desertification.

2011-08-04_20_00_00_Susie_Fire_in_the_Adobe_Range_west_of_Elko_Nevada

To combat this ecosystem overhaul, the most up-to-date and relevant science must be used to guide the restoration of Great Basin plant communities. Improving native plant establishment rates in the restoration setting is one of the biggest challenges faced by land managers.

Bluebunch wheatgrass (Pseudoroegneria spicata) is a commonly used native species in restoration but seedling establishment is modest. The goal of our study is to fill knowledge gaps surrounding seedling adaptation to climate and soils and to provide seed producers with zone specific harvest recommendations.

We hypothesize

1) Bluebunch wheatgrass is adapted to differing soil conditions

2)Through the process of selection, early plant traits such as root-to-shoot ratio, stomatal density, and leaf length have evolved in response to local climate.

3) The timing and duration of the seed production in bluebunch wheatgrass varies with climate and population.

IMG_20160108_115538621We will complete four studies. The soils study will utilize existing phenotypic trait data and soils maps to explore links between soil order, soil series, plant traits, seed zones, and ecoregions. We predict that phenotypic trait divergence will be correlated to soil gradients that exist across seed zones.

The seedling study will relate phenotypic trait variability in twenty-four bluebunch wheatgrass populations to existing seed zones. We predict that seed zones will account for the observed variability in these traits.

The stomate study will compare population stomatal density to aridity. We predict that there is a negative correlation between stomatal density and aridity.

Lastly, we will examine seed production phenology at a common garden near the Crooked River Grasslands. We predict that both the timing and duration of the seed production in bluebunch wheatgrass will vary with climate and seed zone.

Information obtained from this work will either support current seed zones for bluebunch wheatgrass or create better seed zones, and help land managers to achieve higher success rates in restoration.