The intra-plant plasticity of leaves plays a vital role in enabling plants to adapt to changing climatic conditions. However, limited research has investigated the extent of intra-plant leaf trait variation and leaf biomass allocation strategies in herbaceous plants. To address this gap, we collected a total of 1746 leaves from 217 Lamium barbatum Siebold and Zucc. plants and measured their leaf dry mass (M) and leaf area (A). Leaves were categorized by vertical position (upper vs. lower canopy layer) and leaf–shoot orientation (east, south, west, north). ANOVA with Tukey’s HSD test was used to compare differences in M, A, and leaf dry mass per unit area (LMA). Reduced major axis regression was employed to evaluate the scaling relationship between M and A, and the bootstrap percentile method was used to determine differences in scaling exponents. The data indicated that: (i) M, A, LMA, and the scaling exponents of M versus A did not differ significantly among leaf–shoot orientations, and (ii) lower layer leaves exhibited significantly greater M, A, and LMA than upper layer leaves, but their scaling exponents were significantly smaller. These findings highlight that plant vertical growth brings significant intra-plant plasticity in leaf traits and their scaling relationships in herbaceous plants. This plasticity differs from that observed in trees, but is also critical for balancing weight load and optimizing light-use efficiency, potentially enhancing stress resilience in herbaceous plants.

Microplastics exert toxic effects on aquatic plants, thereby impacting ecosystem functions and services. Currently, research on the effects of nanoplastics on aquatic plants has mainly focused on algae, while floating macrophytes have received less attention. To investigate the physiological responses and uptake and accumulation effects of floating macrophytes to polystyrene nanoplastics (PS-NPs), we exposed Limnobium laevigatum, Pistia stratiotes and Eichhornia crassipes to 0.1, 1 and 10 mg·L⁻¹ of PS-NPs (20/100 nm) for 45 days. The results showed that, in general, with increasing concentration and exposure time, the three plant species exhibited a decrease in chlorophyll content, a decline in root activity, an increase in cell membrane permeability and an up-regulation of antioxidant enzyme activities. Meanwhile, the contents of proline, soluble sugars and soluble proteins showed dynamic changes. These findings indicate that under PS-NPs stress, the plants suffered structural damage and they alleviated oxidative injury and maintained osmotic balance by actively accumulating osmoregulatory substances and up-regulating antioxidant enzyme activities. Furthermore, the effects of uptake and accumulation PS-NPs differed among species. At low concentration levels, Limnobium laevigatum exhibits higher uptake and accumulation potential, while at high concentrations, Pistia stratiotes demonstrates greater uptake and accumulation potential.