Leaf Functional Traits of Invasive Grasses Conferring High-Cadmium Adaptation Over Natives

Abstract

Heavy metal (HM) contamination resulting from industrialization and urbanization during the Anthropocene along with plant invasion can severely threaten the growth and adaptation of local flora. Invasive alien plant species generally exhibit a growth pattern consistent with their functional traits in non-contaminated environments in the introduced range. However, it remains unclear whether invasive alien plants have an advantage over native plants in contaminated environments and whether this growth pattern is dependent on the adaptation of their leaf functional traits. Here, we selected two congeneric pairs of invasive alien and native grasses that naturally co-exist in China and are commonly found growing in contaminated soil. To evaluate the effect of cadmium (Cd) on the structural and physiological leaf traits, we grew all four species in soil contaminated without or with 80 mg/kg Cd. Invasive plants contained significantly higher concentrations of Cd in all three organs (leaf, stem, and root). They displayed a higher transfer factor and bioconcentration factor (BCF) of shoot and root than natives, indicating that invasive species are potential Cd hyperaccumulators. Invasive plants accumulated polyphenol oxidase (PPO) to higher levels than natives and showed similar patterns of leaf structural and physiological traits in response to changes in Cd bioconcentration. The quantifiable leaf structural traits of invasive plants were significantly greater (except for stomatal density and number of dead leaves) than native plants. Leaf physiological traits, chlorophyll content, and flavonoid content were also significantly higher in invasive plants than in natives under Cd stress conditions after 4 weeks, although nitrogen balance index (NBI) showed no significant difference between the two species. Chlorophyll fluorescence parameters decreased, except for the quantum yield of photosystem II (ΦPSII) and the proportion of open photosystem II (qP), which increased under Cd stress conditions in both species. However, invasive plants exhibited higher fluorescence parameters than natives under Cd stress, and the decrement observed in invasive plants under Cd stress was greater than that in natives. High Cd adaptation of invasive grasses over natives suggests that invasive plants possess optimal leaf structural and physiological traits, which enable them to adapt to stressful conditions and capture resources more quickly than natives. This study further emphasizes the potential invasion of alien plants in contaminated soil environments within the introduced range. To a certain extent, some non-invasive alien plants might adapt to metalliferous environments and serve as hyperaccumulator candidates in phytoremediation projects in contaminated environments.

Nitrogen enrichment alters the resistance of a noninvasive alien plant species to Alternanthera philoxeroides invasion

“…However, a high N content in plants will increase their palatability and thus their susceptibility to herbivores by changing the interactions with high-trophic-level organisms; this might weaken the defensive ability of A. philoxeroides to resist insect feeding compared to O. articulata in their symbiotic communities (Lu et al, 2015;Liu et al, 2018;Waterton et al, 2022). NBI, the chlorophyll/flavonoid ratio of plants, is an important indicator for evaluating plant growth (Ilyas et al, 2022). In this study, nitrogen addition led to an increase in NBI, which increased the chlorophyll content of the plants and benefitted their absorption and transformation of light energy, thus enhancing their growth (Deng et al, 2019).…”

Morphoanatomical Responses and Stomatal Conductance in Shaded and Sun-Exposed Broussonetia papyrifera Seedlings

“…Morphoanatomical responses of invasive plant species, such as leaf features, root systems, and growth patterns, shed light on their adaptive strategies and competitive advantage in the introduced range (Ilyas et al 2022). Plant functional traits enhance resource acquisition, colonization, and competitive abilities, explaining invasive species' performance within an invaded area (Kaushik et al 2022).…”