Interaction of Light Intensity and CO2 Concentration Alters Biomass Partitioning in Chrysanthemum

Biomass partitioning is one of the pivotal determinants of crop growth management, which is influenced by environmental cues. Light and CO₂ are the main drivers of photosynthesis and biomass production in plants. In this study, the effects of CO₂ levels: ambient 400 ppm (a[CO₂]) and elevated to 1,000 ppm (e[CO₂]) and different light intensities (75, 150, 300, 600 μmol·m⁻²·s⁻¹ photosynthetic photon flux density – PPFD) were studied on the growth, yield, and biomass partitioning in chrysanthemum plants. The plants grown at higher light intensity had a higher dry weight (DW) of both the vegetative and floral organs. e[CO₂] diminished the stimulating effect of more intensive light on the DW of vegetative organs, although it positively influenced inflorescence DW. The flowering time in plants grown at e[CO₂] and light intensity of 600 μmol·m⁻²·s⁻¹ occurred earlier than that of plants grown at a[CO₂]. An increase in light intensity induced the allocation of biomass to inflorescence and e[CO₂] enhanced the increasing effect of light on the partitioning of biomass toward the inflorescence. In both CO₂ concentrations, the highest specific leaf area (SLA) was detected under the lowest light intensity, especially in plants grown at e[CO₂]. In conclusion, elevated light intensity and CO₂ direct the biomass toward inflorescence in chrysanthemum plants.