Exceptional nitrogen-resorption efficiency enables Maireana species (Chenopodiaceae) to function as pioneers at a mine-restoration site

Comparative Insights into Photosynthetic, Biochemical, and Ultrastructural Mechanisms in Hibiscus and Pelargonium Plants

Understanding photosynthetic mechanisms in different plant species is crucial for advancing agricultural productivity and ecological restoration. This study presents a detailed physiological and ultrastructural comparison of photosynthetic mechanisms between Hibiscus (Hibiscus rosa-sinensis L.) and Pelargonium (Pelargonium zonale (L.) L'Hér. Ex Aiton) plants. The data collection encompassed daily photosynthetic profiles, responses to light and CO2, leaf optical properties, fluorescence data (OJIP transients), biochemical analyses, and anatomical observations. The findings reveal distinct morphological, optical, and biochemical adaptations between the two species. These adaptations were associated with differences in photochemical (AMAX, E, Ci, iWUE, and α) and carboxylative parameters (VCMAX, ΓCO2, gs, gm, Cc, and AJMAX), along with variations in fluorescence and concentrations of chlorophylls and carotenoids. Such factors modulate the efficiency of photosynthesis. Energy dissipation mechanisms, including thermal and fluorescence pathways (ΦPSII, ETR, NPQ), and JIP test-derived metrics highlighted differences in electron transport, particularly between PSII and PSI. At the ultrastructural level, Hibiscus exhibited optimised cellular and chloroplast architecture, characterised by increased chloroplast density and robust grana structures. In contrast, Pelargonium displayed suboptimal photosynthetic parameters, possibly due to reduced thylakoid counts and a higher proportion of mitochondria. In conclusion, while Hibiscus appears primed for efficient photosynthesis and energy storage, Pelargonium may prioritise alternative cellular functions, engaging in a metabolic trade-off.

Calcicole-calcifuge plant strategies limit restoration potential in a regional semi-arid flora

AIM

To examine calcicole and calcifuge plant strategies, as well as nutrient-acquisition strategies, as drivers of the distribution of species in response to edaphic factors, and the degree to which these strategies may act as filters to species establishment in ecological restoration on heavily altered or reconstructed substrates.

LOCATION

An 82,000-ha area within a major mining province in the Mid-West region of Western Australia, harboring vegetation communities ranging from species-poor halophytic scrub on saline flats to dense biodiverse shrubland on the skeletal soils of ancient Banded Ironstone Formations (BIF).

METHODS

Univariate and multivariate analyses were employed to examine how variation in soil chemistry and landscape position (undulating plains, slopes, and BIF crests and ridges) influenced patterns of floristic diversity, calcifuge plant strategies, and nutrient-acquisition strategies in 538 plant species from 830 relevés.

RESULTS

Landscape position was the strongest driver of species richness and vegetation functional composition. Soils became increasingly acidic and P-impoverished along an increasing elevational gradient. Vegetation from different landscape positions was not compositionally dissimilar, but vegetation of BIF crests and ridges was up to twice as biodiverse as vegetation from adjacent lower-relief areas and harbored higher proportions of calcifuge species and species with mycorrhizal associations.

MAIN CONCLUSIONS

Topographic and edaphic complexity of BIF landforms in an otherwise relatively homogenous landscape has likely facilitated species accumulation over long time periods. They represent musea of regional floristic biodiversity, excluding only species that cannot establish or are inferior competitors in heavily weathered, acidic, skeletal, and nutrient-impoverished soils. Plant strategies likely represent a major filter in establishing biodiverse, representative vegetation on postmining landforms in geologically ancient regions.