Koga Hiroyuki, Doll Yuki, Hashimoto Kei, Toyooka Kiminori, Tsukaya Hirokazu
Graduate School of Science, The University of Tokyo, Tokyo, Japan.
RIKEN Center for Sustainable Resource Science, Yokohama, Japan.
Front Plant Sci. 2020 Mar 10;11:269. doi: 10.3389/fpls.2020.00269. eCollection 2020.
Heterophylly, or phenotypic plasticity in leaf form, is a remarkable feature of amphibious plants. When the shoots of these plants grow underwater, they often develop surprisingly different leaves from those that emerge in air. Among aquatic plants, it is typical for two or more distinct leaf development processes to be observed in the same individual exposed to different environments. Here, we analyze the developmental processes of heterophylly in the amphibious plant L. (Plantaginaceae). First, we reliably cultured this species under laboratory conditions and established a laboratory strain. We also established a framework for molecular-based developmental analyses, such as whole-mount hybridization. We observed several developmental features of aerial and submerged leaves, including changes in form, stomata and vein formation, and transition of the meristematic zone. Then we defined developmental stages for leaves. We found that in early stages, aerial and submerged leaf primordia had similar forms, but became discriminable through cell divisions with differential direction, and later became highly distinct via extensive cell elongation in submerged leaf primordia.
异形叶性，即叶片形态的表型可塑性，是两栖植物的一个显著特征。当这些植物的茎在水下生长时，它们通常会长出与在空气中长出的叶子截然不同的叶子。在水生植物中，在暴露于不同环境的同一个体中观察到两个或更多不同的叶片发育过程是很典型的。在这里，我们分析了两栖植物大车前（车前科）异形叶性的发育过程。首先，我们在实验室条件下可靠地培养了该物种并建立了一个实验室菌株。我们还建立了基于分子的发育分析框架，如整体杂交。我们观察了气生叶和沉水叶的几个发育特征，包括形态变化、气孔和叶脉形成以及分生组织区的转变。然后我们定义了叶片的发育阶段。我们发现，在早期阶段，气生叶和沉水叶原基具有相似的形态，但通过不同方向的细胞分裂变得可区分，后来通过沉水叶原基中广泛的细胞伸长变得高度不同。
