Investigating the single and interactive effects of the main components of climate change (higher temperature, elevated CO₂, and water stress) on plants is crucial to our understanding of plant performance under future climate. We studied the effects of these factors on black knapweed (Centaurea nigra). Plants were grown under 2 temperature regimes (22/18 °C and 28/24 °C), 2 CO₂ concentrations (380 and 760 µmol·mol^-1), and 2 watering regimes (well watered and water stressed) in growth chambers, and their growth and physiological parameters, including biomass, growth indices, chlorophyll fluorescence, photosynthetic pigments, and ethylene evolution, were measured. We found that interactions among the 3 components of climate change primarily affected shoot and total biomass and specific leaf mass. Overall, higher temperature and water stress have negative effects, whereas elevated CO₂ has positive effects on C. nigra. Nevertheless, the negative effects of higher temperature and water stress stimulate adaptive responses by this species. Also, elevated CO₂ mitigates some of the adverse effects of these stress factors and regulates the plant's adaptive mechanism. It is likely that invasive weeds such as C. nigra have the potential to take advantage of climate changes, becoming more competitive and possibly posing significant challenges to maintaining indigenous biodiversity in the future.

Nomenclature: Kartesz, 1994; Darbyshire, 2003.