The effects of physiological integration on biomass partitioning in plant modules: an experimental study with the stoloniferous herb Glechoma hederacea

Morphological and physiological plasticity are crucial attributes enabling plants to acquire resources from heterogeneous habitats. Although physiological integration can modify biomass partitioning in modules, especially when connected modules experience different conditions, its ecological importance has been largely overlooked. This experiment examined its effects on above- and belowground biomass partitioning by modules in the stoloniferous herb Glechoma hederacea. We studied how biomass allocation to roots by younger ramets was affected by connection to older ramets, and by nutrient conditions. A lower proportion of biomass was allocated to roots by younger ramets growing under low nutrient (LN) conditions when connected to older ramets in high nutrient (HN) conditions than when they were isolated, demonstrating localised modification of biomass partitioning due to physiological integration. The proportion of biomass allocated to roots by younger ramets was also lower when connected to older ramets in HN conditions than when connected to older ramets in LN conditions. Thus, the effect of integration on biomass partitioning depended on the nutrient conditions experienced by connected ramets. Such changes in biomass partitioning would result in more extensive stolon growth, and greater lateral displacement of new ramets. Understanding the ecological implications of phenotypic plasticity in plants will require further examination of the effects of physiological integration when connected modules experience contrasting growing conditions. This study demonstrates that such integration affects the biomass allocation strategy of connected ramets, enhancing resource acquisition in heterogeneous habitats. The widespread success of clonality in many communities is likely to be strongly promoted by this characteristic.