Effects of temporal heterogeneity in nutrient supply on intra- and inter-genet competition of a clonal herb

Effects of clonal integration and nutrient availability on the growth of Glechoma longituba under heterogenous light conditions

Introduction

Clonal integration of connected ramets within clones is an important ecological advantage. In this study, we tested the hypothesis that the effects of clonal integration on performance of donor and recipient ramets when one resource is heterogeneous can be influenced by the availability of another resource of donor ramets.

Methods

We conducted a greenhouse experiment on the widespread, perennial herb Glechoma longituba. Clonal fragments consisting of pairs of connected ramets were grown for seven weeks. The younger, apical ramets were exposed under 30% or 100% light condition and the older, basal ramets were treated with three levels of nutrients. The connections between ramets were either severed or left intact. 30% light condition negatively affected the growth of apical ramets, basal ramets and the whole fragments.

Results

Clonal integration significantly increased the growth of apical ramets, but decreased the growth of the basal ramets. Medium and high level nutrient availability of basal ramets significantly increased the growth of apical ramets, basal ramets and the whole fragments. At the high nutrient level, the reduction in growth of basal ramets from clonal integration was decreased, but the growth responses of apical ramets and the whole fragments to clonal integration were not influenced by nutrient availability.

Conclusion

The results suggested that clonal integration was benefit to the growth of apical ramets of Glechoma longituba but at the cost of reducing the growth of basal ramets. Although the high nutrient level could reduce the cost that clonal integration brought to the unshaded basal ramets, but could not increase the benefit that clonal integration brought to the shaded apical ramets and whole fragment.

Halophytic Clonal Plant Species: Important Functional Aspects for Existence in Heterogeneous Saline Habitats

Plant modularity-related traits are important ecological determinants of vegetation composition, dynamics, and resilience. While simple changes in plant biomass resulting from salt treatments are usually considered a sufficient indicator for resistance vs. susceptibility to salinity, plants with a clonal growth pattern show complex responses to changes in environmental conditions. Due to physiological integration, clonal plants often have adaptive advantages in highly heterogeneous or disturbed habitats. Although halophytes native to various heterogeneous habitats have been extensively studied, no special attention has been paid to the peculiarities of salt tolerance mechanisms of clonal halophytes. Therefore, the aim of the present review is to identify probable and possible halophytic plant species belonging to different types of clonal growth and to analyze available scientific information on responses to salinity in these species. Examples, including halophytes with different types of clonal growth, will be analyzed, such as based on differences in the degree of physiological integration, ramet persistence, rate of clonal expansion, salinity-induced clonality, etc.

Density Alters Impacts of Genotypic Evenness on Productivity in an Experimental Plant Population

Genetic diversity plays important roles in maintaining population productivity. While the impact of genotypic richness on productivity has been extensively tested, the role of genotypic evenness has not been considered. Plant density can also affect population productivity, but its interaction with genotypic diversity has not been tested. We constructed experimental populations of the clonal plant Hydrocotyle vulgaris with either low or high richness (consisting of four vs. eight genotypes), either low or high evenness (each genotype had a different number vs. the same number of ramets), and either low or high density (consisting of 16 vs. 32 ramets) in a full factorial design. Total biomass of plant populations did not differ between four- and eight-genotype mixtures. When the initial plant density was low, total biomass of populations with high genotypic evenness was significantly greater than total biomass of those with low genotypic evenness. However, this difference disappeared when the initial plant density was high. Moreover, total biomass increased linearly with increasing plant density at harvest, but was negatively correlated to variation in leaf area. We conclude that genotypic evenness but not genotypic richness can benefit population productivity, and that plant density can alter the impact of genotypic evenness on population productivity.