摘要：The growth pattern of the seagrass Zostera noltii is described through the analysis of the shoot primordium organization within different shoot types using optical and scanning electron microscopy. Both histological approaches showed that Z. noltii shoots are organized by a successive repetition of a unit named “phytomer” (shoot primordium, node, internode, root, sheath and leaf), in resemblance with the shoot structure described for land grasses. This study showed that differences among shoot types are determined by two factors: (1) the presence or absence of some of the fundamental parts (mainly shoot primordium) in the “phytomer”, (2) the evolvement stage of these elements. The branching of Z. noltii was limited by shoot structure and shoot primordium arrangement; in the “natural” branching pattern the first axillary shoot branched opposite to the previous branch. Simulation of the topology of a Z. noltii plant using the “natural” branching pattern, and its opposite one, with two different branching angles for each pattern, showed that the reduction in the branching angle notably decreases the colonizing efficiency (ca. 25% from 90 to 45°). Changes in the timing of shoot primordium development and/or release, and the optimization of the branching angle in response to external forcing (light, nutrients, density, etc.) may elucidate species-specific differences and colonization strategies with respect to abiotic conditions.
