Clonal Plants as Meta-Holobionts

Organization of a clonal plant, sequential growth, and plastic responses in heterogeneous environments. (Top left) Clonal fragments are composed of ramets linked through connections that can be aboveground or belowground (see supplemental material for vocabulary definitions). (Bottom left) Clonal growth is sequential and multiplies ramets and connections. A clonal fragment can be split due to physical injury or connection life span. (Right) Clonal fragments display particular plastic responses unique to clonal plants that are “foraging behavior” (a), “specialization for abundance” (b), and “division of labor” (c). Foraging behavior consists of aggregating the ramets in rich patches (brown) and avoiding poor patches (gray). Plastic responses may include connection length, direction of growth, and intensity of ramification. Specialization for abundance describes when ramets locally invest in organs that uptake the most abundant resource and share this resource to the other ramets thanks to physiological integration. Division of labor is an extension of specialization when the environment presents two resources that are negatively correlated (such as light and soil resources). Ramets thus display high aboveground allocation under high-light and low-nutrient conditions, whereas the belowground allocation is high under the reverse conditions.