Of puzzles and pavements: a quantitative exploration of leaf epidermal cell shape

Epidermal cells of leaves are diverse: tabular pavement cells, trichomes, and stomatal complexes. Pavement cells from the monocot Zea mays (maize) and the eudicot Arabidopsis thaliana (Arabidopsis) have highly undulate anticlinal walls. The molecular basis for generating these undulating margins has been extensively investigated in these species. This has led to two assumptions: first, that particular plant lineages are characterized by particular pavement cell shapes; and second, that undulatory cell shapes are common enough to be model shapes. To test these assumptions, we quantified pavement cell shape in epidermides from the leaves of 278 vascular plant taxa. We found that monocot pavement cells tended to have weakly undulating margins, fern cells had strongly undulating margins, and eudicot cells showed no particular undulation degree. Cells with highly undulating margins, like those of Arabidopsis and maize, were in the minority. We also found a trend towards more undulating cel...叶片表皮细胞类型多样，包含扁平表皮细胞（tabular pavement cell）、毛状体（trichome）与气孔复合体（stomatal complex）。来自单子叶植物玉蜀黍（Zea mays，简称玉米）与双子叶植物拟南芥（Arabidopsis thaliana，简称Arabidopsis）的扁平表皮细胞，其垂周壁（anticlinal wall）呈高度波浪状。针对这两个物种中形成此类波浪状细胞边缘的分子基础，学界已开展大量深入研究。由此衍生出两项假设：其一，特定植物支系以特定的扁平表皮细胞形态为典型特征；其二，波浪状细胞形态足够普遍，可作为研究模型形态。 为验证上述两项假设，我们对278个维管植物类群（vascular plant taxa）的叶片表皮开展了扁平表皮细胞形态量化分析。 研究发现，单子叶植物的扁平表皮细胞边缘通常呈弱波浪状，蕨类植物的扁平表皮细胞边缘呈强波浪状，而双子叶植物的扁平表皮细胞未表现出特定的波浪程度。高度波浪状边缘的细胞（如拟南芥与玉米的表皮细胞）仅占少数。我们还发现细胞波浪程度呈愈发……的趋势。