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.

Growth Responses of Avicennia germinans and Batis maritima Seedlings to Weathered Light Sweet Crude Oil Applied to Soil and Aboveground Tissues

Oil spills are a significant stressor to coastal and maritime environments worldwide. The growth responses of Batis maritima and Avicennia germinans seedlings to weathered Deepwater Horizon oiling were assessed through a mesocosm study using a factorial arrangement of 4 soil oiling levels (0 L m-2, 1 L m-2, 2 L m-2, 4 L -m-2) x 3 tissue oiling levels (0% of stem height, 50% of stem height, 100% of stem height). Overall, growth metrics of B. maritima displayed much greater sensitivity to both tissue and soil oiling than A. germinans, which exhibited a relatively high tolerance to both routes of oiling exposure. Batis maritima in the 4 L m-2 soil oiling treatment demonstrated significant reductions in cumulative stem height and leaf number, whereas no significant effects of soil oiling on A. germinans were detected. This was reflected in end of the study biomass partitioning, where total aboveground and live aboveground biomass were significantly reduced for B. maritima with 4 L m-2 soil oiling, but no impacts to A. germinans were found. Tissue oiling of 100% did appear to initially reduce B. maritima stem diameter, but no effect of tissue oiling was discerned on biomass partitioning, suggesting that there were no impacts to integrated growth. These findings suggest that B. maritima would be more severely affected by heavy soil oiling than A. germinans.

Blue Light Improves Photosynthetic Performance and Biomass Partitioning toward Harvestable Organs in Saffron (Crocus sativus L.)

Saffron is a valuable plant and one of the most expensive spices worldwide. Nowadays, there is a tendency to produce this crop in indoor plant production systems. However, the production of saffron is restricted by the need for the reproduction of high-quality corms. In this study, we investigated the effect of different ratios of red (R) and blue (B) light spectra (including 100% B (monochromatic B), 75%, 50%, 40%, 25% B, and 0% B (monochromatic R) on the photosynthetic performance and biomass partitioning as well as morphological and biochemical characteristics of saffron. The growth of flower, root, and corm was improved by increasing the proportion of B to R light. B-grown plants were characterized by the highest photosynthetic functionality with efficient electron transport and lower energy dissipation when compared to R-grown plants. B light directed biomass toward the corms and floral organs, while R light directed it toward the leaves. In saffron, the weight of a daughter corm is of great importance since it determines the yield of the next year. As the ratio of B to R light increased, the daughter corms also became heavier, at the cost of reducing their number, though increasing the proportion of B-enhanced antioxidant capacity as well as the activity of ascorbate peroxidase and catalase while superoxide dismutase activity was enhanced in R-grown plants. In conclusion, B light increased the production of high-quality daughter corms and altered biomass partitioning towards harvestable organs (corms and flowers) in saffron plants.