Effects of nitrogen addition on clonal integration between mother and daughter ramets of Moso bamboo: a 13C-CO2 pulse labeling study

Aims Resource sharing among connected ramets (i.e., clonal integration) is one of the distinct traits of clonal plants. Clonal integration confers Moso bamboo (Phyllostachys pubescens) a strong adaptability to different environmental conditions. But the mechanisms of how clonal integration makes Moso bamboo has better performance are still poorly understood. In this study, acropetal and basipetal translocation of photosynthates between Moso bamboo ramets were analyzed separately, to investigate how clonal fragments obtain higher benefits under heterogeneous N conditions. Methods Clonal fragments of Moso bamboo consisting of two interconnected mother-daughter ramets were used, each of the ramets was subjected to either with or without N addition. The acropetal and basipetal translocation of 13C-photosynthates were separated via single-ramet 13CO2-labeling. Important Findings Mother ramets translocated more 13C-photosynthates to daughter ramets with N addition, and the translocation of 13C-photosynthates to mother ramets was more pronounced when daughter ramets were treated with N addition. The 13C-photosynthates that were translocated from mother ramets without and with N addition were mainly invested in the leaves and roots of daughter ramets with N addition, from daughter ramets with N addition were mainly invested in the leaves and roots of mother ramets with and without N addition, respectively. These results suggest that mother ramets preferentially invest more resources in nutrient-rich daughter ramets, and that daughter ramets serve as efficient resource acquisition sites to specialize in acquiring abundant resources based on the resource conditions of mother ramets. Clonal plants can improve their resource acquisition efficiency and maximize the overall performance through this way.

Opposing effects of plant growth regulators via clonal integration on apical and basal performance in alligator weed

Aims Invasive plants are a major threat to biodiversity and may adversely affect food security. Clonal integration enables the sharing of resources between connected ramets and can enhance plant performance in many invasive species. However, few studies have examined the role of clonal integration when weeds are exposed to plant growth regulators (PGRs). PGRs are used extensively in agriculture and may affect nearby weeds through soil leaching, erosion, and runoff. Our aim was to investigate the effects of clonal integration on growth in a noxious weed, Alternanthera philoxeroides (alligator weed), in response to two PGRs frequently used in agriculture, gibberellins (GA) and paclobutrazol (PAC). Methods Ramets of A. philoxeroides were propagated in the greenhouse, and treated with PGRs. PGRs were applied to the older ramets (i.e., ‘basal’ part), with half of the plants having the stems between the apical (younger) and basal parts left connected, while the remaining plants had the stems between the two parts severed. Following the growing period, plants were measured for growth traits. Important Findings We found that GA and PAC had contrasting effects on plant growth. GA significantly promoted above-ground growth of the apical ramets via clonal integration. Alternatively, PAC inhibited above-ground growth in the basal and apical parts, and enhanced below-ground growth of the basal and apical ramets through clonal integration. Our results highlight how clonal integration can promote growth in A. philoxeroides following the application of PGRs, which is likely an important mechanism for this species to invade new environments.

Effects of clonal integration, nutrients and cadmium on growth of the aquatic macrophyte Pistia stratiotes

Aims Many wetlands are polluted with both nutrients and toxic metals and vegetated largely by clonal plants. We hypothesized that eutrophication and clonal integration can increase phytoremediation of toxic metal pollution by increasing plant growth, even under the stress imposed by toxicity. Methods To test this hypothesis, single ramets of the common, widespread, floating, stoloniferous plant Pistia stratiotes L., were grown for 42 days at two levels of nutrient availability with and without 0.6 mg L−1 cadmium. Ramets were either severed from their vegetative offspring to prevent clonal integration or left connected, and severed offspring were either removed to eliminate intraclonal competition or left in place. Important Findings Plants subjected to cadmium addition accumulated almost twice as much dry mass if given the higher nutrient level, due mainly to a doubling of the number of clonal offspring. Severance had little effect on the final mass of the parent plus offspring ramets. Removing offspring following severance had no effect on the final mass of the parental ramet in the presence of added cadmium, but it did increase the final mass of the parent in the absence of cadmium. These results support the hypothesis that eutrophication can increase remediation of toxic metal pollution by aquatic macrophytes but provided no evidence that clonal integration can affect remediation. Species such as P. stratiotes may help remediate co-pollution of wetlands with toxic metals and nutrients, and fragmentation of clones may not affect their remediation capacity.