Distinct responses of frond and root to increasing nutrient availability in a floating clonal plant

The complete chloroplast genome sequence of Hydrocotyle vulgaris L. (Araliaceae)

Hydrocotyle vulgaris is a perennial wetland clonal plant in the Araliaceae family, which was introduced to China as an ornamental plant in the 1990s. Although H. vulgaris is now considered a potential invasiveness species in China, it also plays a significant role in the remediation of water pollution. Here, we reported its complete chloroplast genome and analyzed the basic characteristics. The chloroplast genome was 153,165 bp in length, including a pair of inverted repeat (IR) regions of 25,072 bp separated by a large single-copy (LSC) region of 84,291 bp and a small single-copy (SSC) region of 18,730 bp. The H. vulgaris chloroplast genome contained 132 predicted genes, and its overall GC content was 37.60%. Phylogenetic analysis revealed that H. vulgaris was closely related to H. verticillata. The H. vulgaris chloroplast genome presented in this study will lay a foundation for further genetic and genomic studies of the genus Hydrocotyle.

Transgenerational plasticity in morphological characteristics and biomass of the invasive plant Xanthium strumarium

Transgenerational plasticity (TGP) allows a plant to acclimate to external variable environments and is a potential mechanism that explains the range expansion and invasion success of some exotic plants. Most studies explored the traits of TGP associated with the success of exotic plant invasions by comparison studies among exotic, native, invasive, and noninvasive species. However, studies on the TGP of invasive plants in different resource environments are scarce, and the biological mechanisms involved are not well understood. This study aimed to determine the role of TGP in the invasiveness of Xanthium strumarium in northeast China. We measured the plant morphology of aboveground parts and the growth of three generations of the invader under different environmental conditions. The results showed that the intergenerational plasticity of X. strumarium was stronger under stress conditions. We found that the X. strumarium parent generation (F0) grown under water and/or nutrient deficiency conditions transferred the environmental information to their offspring (F1 and F2). The F1 generation grown under high-resource conditions has greater height with larger crown sizes, thicker basal diameters, and higher biomass. Both water and nutrients can affect the intergenerational transmission of plant plasticity, nutrients play a more important role compared with water. The high morphological intergenerational plasticity of X. strumarium under a pressure environment can help it quickly adapt to the new environment and accelerate the rapid expansion of the population in the short term. The root:shoot ratio and reproductive and nutrient distribution of the X. strumarium F0 and F1 generations showed high stability when the growth environment of the F0 generation differed from that of the F1 generation. The stable resource allocation strategy can ensure that the obtained resources are evenly distributed to each organ to maintain the long-term existence of the community. Therefore, the study of intergenerational transmission plasticity is of great significance for understanding the invasion process, mechanism, and prevention of invasive plants.

Cadmium stress interacts with nutrient availability and light condition to affect the growth of Hydrocotyle vulgaris

Heavy metal pollution is becoming a serious problem in wetland and often co-occurs with nutrient availability and light conditions variation. We hypothesized that nutrient availability and light condition can affect the growth of wetland plants under heavy metal stress. To test this hypothesis, single ramets of a common, clonal wetland plant Hydrocotyle vulgaris were grown for four weeks at three levels of cadmium with three levels of nutrient availability under 30% or 100% light conditions. High level of nutrient availability and high light condition overall promoted growth of H. vulgaris under Cd stress. Under the two light conditions, responses of H. vulgaris to Cd treatments differed among three nutrient levels. Under 30% light condition, 2 mg L-1 Cd2+ treatment decreased total mass at the low nutrient level and decreased ramet number at the medium nutrient level; 0.5 and 2 mg L-1 Cd2+ treatments decreased leaf mass ratio at the low and the medium nutrient levels. Under 100% light condition, 2 mg L-1 Cd2+ treatments significantly decreased total mass at the high level of nutrients; 2 mg L-1 Cd2+ treatment decreased ramet number at the medium and the high nutrient levels and decreased leaf mass ratio at the medium nutrient levels. Our results suggested that Cd stress can interact with nutrient availability and light condition to affect the performance of wetland plants such as H. vulgaris.