Rudall Paula J, Chen Elisabeth D, Cullen Erin
Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK.
Am J Bot. 2017 Aug;104(8):1122-1141. doi: 10.3732/ajb.1700086.
Leaves of monocots are typically linear with parallel venation, though a few taxa have broad leaves. Studies of stomatal patterning and development in monocots required updating in the context of rapidly improving knowledge of both the phylogenetic and development-genetic context of monocots that facilitate studies of character evolution.
We used an existing microscope-slide collection to obtain data on stomatal structure across all the major monocot clades, including some species with relatively broad leaves. In addition, we used both light and electron microscopy to study stomatal development in 16 selected species. We evaluated these data in a phylogenetic context to assess stomatal character evolution.
Mature stomatal patterning in monocots can be broadly categorized as anomocytic, paracytic-nonoblique, and paracytic/tetracytic oblique, depending on the presence, development, and arrangement of lateral subsidiary cells. Stomatal meristemoids invariably result from an asymmetric mitosis in monocots. In species where lateral subsidiary cells are present, they are perigene cells. Among monocots with relatively broad leaves, stomatal orientation is linear-axial in most taxa, but transverse in Lapageria and Stemona, and random in Dioscorea and some Araceae. Amplifying divisions are apparently absent in monocots.
Anomocytic stomata represent the likely ancestral (plesiomorphic) condition in monocots, though multiple evolutionary transitions and reversals have occurred. Paracytic-nonoblique stomata with highly modified perigene lateral neighbor cells characterize grasses and other Poales. The presence of anomocytic stomata in Japonolirion and Tofieldia reinforces the concept that these two genera have retained many ancestral monocot features and are critical in understanding character evolution in monocots.
单子叶植物的叶子通常呈线性且叶脉平行，不过也有少数类群具有宽阔的叶子。鉴于在单子叶植物的系统发育和发育遗传学背景知识迅速完善的情况下，有助于性状进化研究，因此有必要更新对单子叶植物气孔模式和发育的研究。
我们利用现有的显微镜载玻片标本集，获取了所有主要单子叶植物分支的气孔结构数据，包括一些具有相对宽阔叶子的物种。此外，我们使用光学显微镜和电子显微镜研究了16个选定物种的气孔发育。我们在系统发育背景下评估这些数据，以评估气孔性状的进化。
单子叶植物成熟的气孔模式大致可分为不规则型、平列型（非斜列）和平列型/四轮列型（斜列），这取决于侧生副卫细胞的存在、发育和排列。在单子叶植物中，气孔分生组织母细胞总是由不对称有丝分裂产生。在有侧生副卫细胞的物种中，它们是周缘细胞。在具有相对宽阔叶子的单子叶植物中，大多数类群的气孔取向是线性轴向的，但在拉帕杰里亚属和百部属中是横向的，在薯蓣属和一些天南星科植物中是随机的。单子叶植物中显然不存在增殖分裂。
不规则型气孔可能代表单子叶植物的祖先（近祖）状态，不过已经发生了多次进化转变和逆转。具有高度特化的周缘侧邻细胞的平列型（非斜列）气孔是禾本科和其他禾本目的特征。日本藜芦属和岩菖蒲属中存在不规则型气孔，强化了这两个属保留了许多单子叶植物祖先特征的概念，并且对于理解单子叶植物的性状进化至关重要。
