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Abstract Detail

Anatomy and Morphology

Gallaher, Timothy [1], Klahs, Phillip [2], Cox, Monica [3], Moss, Kimberly [4], Craine, Joseph [5], Clark, Lynn [6].

Evolutionary and functional aspects of three-dimensional chlorenchyma cell shape in the grasses (Poaceae) and other monocots.

The great utility of leaf anatomy for grass systematics has long been recognized, and leaf anatomical characters are critical to understanding C4 evolution and functionality as well as adaptations to the varied habitats the grasses occupy. However, virtually all leaf anatomical data for the family is derived from leaf cross sections, despite a few hints in the literature of interesting shape variation in the proximo-distal and lateral planes. We therefore conducted a survey of the three-dimensional chlorenchyma cell shape in about 270 grass species representing all subfamilies and most of the tribes, and about 30 non-grass monocots, including the Joinvilleaceae and Flagellariaceae, the leaf-blade producing families closest to the grasses. Adaxial chlorenchyma cells associated with first order vascular bundles were measured for 15 variables. Digital 3D cell models were created using Cinema 4D to estimate cell surface area and volume. Ancestral state reconstruction revealed that most monocots, including Flagellariaceae, have more or less spherical or elongated, large, unlobed adaxial chlorenchyma cells. Chlorenchyma cells of Joinvilleaceae and Poaceae are reduced in size relative to most non-grass monocots, and elongation in the proximo-distal plane is plesiomorphic within the Poaceae although a number of reversals are observed; lobing of adaxial chlorenchyma cells in at least one plane, often the proximo-distal or lateral plane, is also a general feature in the family. Various cell shapes, including some more or less spherical or cylindrical shapes, were inferred. All C4 lineages with the exception of Digitaria (Paniceae, Panicoideae) and a few others converged on a “radiator” cell shape, with lobing visible only in longitudinal and paradermal sections. Digitaria exhibits an “H”-shaped adaxial chlorenchyma cell. Some C3 taxa also exhibit the radiator cell shape, but members of the Pooideae (bluegrasses) with this cell shape have reverted to a larger size. The functional significance of the extensive lobing of grass leaf chlorenchyma cells remains unknown, but it does not appear to be related to C3-C4 anatomical transitions. However, chlorenchyma cells of C3 taxa have greater variability in cell shape than either CAM (among the non-grass monocots) or C4 taxa, indicating a functional constraint on the latter two. ANOVA and pairwise Tukey tests indicate significant differences (p-values <0.01) among surface area to volume ratios for C3, C4, and CAM chlorenchyma cells. Potential correlations of these shapes with climatic variables will also be discussed.

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1 - University Of Washington, Biology, 24 Kincaid Hall, Box 351800, Seattle, WA, 98195, United States
2 - Iowa State University, Ecology, Evolutionary, and Organismal Biology, 251 Bessey Hall, 2200 Osborn Drive, Ames, Iowa, 50011, United States
3 - William Penn University, Career Services, 220 Penn Hall, Oskaloosa, IA, 52577, USA
4 - Iowa State University, Art and Visual Culture, 378 College of Design, Ames, IA, 50011, USA
5 - Jonah Ventures, Manhattan, KS, 66502, USA
6 - Iowa State University, Department Of Ecology, Evolution, And Organismal Biology, 251 Bessey Hall, 2200 Osborn Dr., Ames, IA, 50011, United States

Leaf anatomy
chlorenchyma cell shape
3D modeling.

Presentation Type: Oral Paper
Session: 6, Anatomy and Morphology I
Location: 113/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 11:00 AM
Number: 6012
Abstract ID:811
Candidate for Awards:None

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