Leaf Venation and Morphology Help Explain Physiological Variation in Yucca brevifolia and Hesperoyucca whipplei Across Microhabitats in the Mojave Desert, CA.

Amber R Jolly ,Ugbad Farah,Jessica Lamban Pinlac,Janty Woojuh,Zayra Correa,Edgar Pedroza,Josephina Diaz Calderon,Joseph Zailaa,Monserrat Orozco,Félicia Makaya Libifani,Christina Nguyen,Justin Nava,Jose Cuba,Andoni Miranda,Laura Gastelum,Christian Alex Caranto,Jennyfer Perdomo,Darlene Arzate,Christine Scoffoni,Scott Pezzini,Nancy L Garcia ,Ivette Rubio Gutiérrez ,M E De Haro ,Ho Ming Yuen

doi:10.3389/fpls.2020.578338

Amber R Jolly , Ugbad Farah + Show 22 more

Open Access

https://doi.org/10.3389/fpls.2020.578338

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Abstract

Different microclimates can have significant impact on the physiology of succulents that inhabit arid environments such as the Mojave Desert (California). We investigated variation in leaf physiology, morphology and anatomy of two dominant Mojave Desert monocots, Yucca brevifolia (Joshua tree) and Hesperoyucca whipplei, growing along a soil water availability gradient. Stomatal conductance (gs) and leaf thickness were recorded in the field at three different sites (north-western slope, south-eastern slope, and alluvial fan) in March of 2019. We sampled leaves from three individuals per site per species and measured in the lab relative water content at the time of gs measurements, saturated water content, cuticular conductance, leaf morphological traits (leaf area and length, leaf mass per area, % loss of thickness in the field and in dried leaves), and leaf venation. We found species varied in their gs: while Y. brevifolia showed significantly higher gs in the alluvial fan than in the slopes, H. whipplei was highest in the south-eastern slope. The differences in gs did not relate to differences in leaf water content, but rather to variation in number of veins per mm2 in H. whipplei and leaf width in Y. brevifolia. Our results indicate that H. whipplei displays a higher water conservation strategy than Y. brevifolia. We discuss these differences and trends with water availability in relation to species’ plasticity in morphology and anatomy and the ecological consequences of differences in 3-dimensional venation architecture in these two species.

Highlights

Plants have different physiological thresholds to survive drought and understanding these thresholds can help predict community structure as climate change persists (Choat et al, 2018)
The gs varied from 96.75 ± 2.9 mmol m−2 s−1 in the AF to 57.0 ± 2.7 mmol m−2 s−1 in the SE slope in Y. brevifolia, and from 78.3 ± 4.9 mmol m−2 s−1 to 53.2. ± 3.32 mmol m−2 s−1 in the SE and north-western slope (NW) slope, respectively, in H. whipplei (Figure 3)
We found a significant species-site interaction, with Y. brevifolia growing at the AF having the highest gs (Figure 3)

Summary

Introduction

Plants have different physiological thresholds to survive drought and understanding these thresholds can help predict community structure as climate change persists (Choat et al, 2018). The structure and function of plant populations are greatly determined by the environment, especially in deserts, a quickly growing biome (Cloudsley-Thompson, 1978; Archer and Predick, 2008) where. The Mojave Desert is dominated by winter precipitation making it an ideal home for the iconic Yucca brevifolia, commonly known as the Joshua tree (Archer and Predick, 2008). The standing groves of the Y. brevifolia and another important Mojave Desert succulent, Hesperoyucca whipplei, are threatened because of the ongoing major migration of their ideal habitats due to climate change (Wells and Woodcock, 1985; Cole et al, 2011)

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