Fine Root Length of Maize Decreases in Response to Elevated CO2 Levels in Soil

Quality degradation of alfalfa caused by CO2 leakage from carbon capture and storage

A complete understanding of the potential environmental risks associated with carbon capture and storage (CCS) is critical for its large-scale deployment. Many experiments have simulated plant responses to soil CO₂ stress caused by CCS leakage; however, crop quality has received less attention. This study assessed the effects of leaked CO₂ from CCS on alfalfa yield and nutritional quality using pot experiments, focusing on crude protein and amino acids to address this knowledge gap. Our results showed that the aboveground and underground fresh weights decreased by 43.55 % and 66.06 %, respectively. The root-to-shoot ratio of alfalfa decreased from 1.04 to 0.63, indicating greater inhibition effects on the root than on the aboveground part of alfalfa. Crude protein and total amino acids in alfalfa declined by approximately 15.20 % and 11.37 %, respectively, compared to the non-leaked scenario. Our findings could potentially shed light on the environmental impact of CCS leakage, explicitly concerning the decline of crop quality, which adds to existing knowledge of the environmental effects of CCS failure.

Enriched CO2 and Root-Associated Fungi (Mycorrhizae) Yield Inverse Effects on Plant Mass and Root Morphology in Six Asclepias Species

While milkweeds (Asclepias spp.) are important for sustaining biodiversity in marginal ecosystems, CO2 flux may afflict Asclepias species and cause detriment to native communities. Negative CO2-induced effects may be mitigated through mycorrhizal associations. In this study, we sought to determine how mycorrhizae interacts with CO2 to influence Asclepias biomass and root morphology. A broad range of Asclepias species (n = 6) were chosen for this study, including four tap-root species (A. sullivantii, A. syriaca, A. tuberosa, and A. viridis) and two fibrous root species (A. incarnata and A. verticillata). Collectively, the six Asclepias species were manipulated under a 2 × 2 full-factorial design that featured two mycorrhizal levels (-/+ mycorrhizae) and two CO2 levels (ambient and enriched (i.e., 3.5× ambient)). After a duration of 10 months, Asclepias responses were assessed as whole dry weight (i.e., biomass) and relative transportive root. Relative transportive root is the percent difference in the diameter of highest order root (transportive root) versus that of first-order absorptive roots. Results revealed an asymmetrical response, as mycorrhizae increased Asclepias biomass by ~12-fold, while enriched CO2 decreased biomass by about 25%. CO2 did not impact relative transportive roots, but mycorrhizae increased root organ's response by more than 20%. Interactions with CO2 and mycorrhizae were observed for both biomass and root morphology (i.e., relative transportive root). A gene associated with CO2 fixation (rbcL) revealed that the two fibrous root species formed a phylogenetic clade that was distant from the four tap-root species. The effect of mycorrhizae was most profound in tap-root systems, as mycorrhizae modified the highest order root into tuber-like structures. A strong positive correlation was observed with biomass and relative transportive root. This study elucidates the interplay with roots, mycorrhizae, and CO2, while providing a potential pathway for mycorrhizae to ameliorate CO2 induced effects.

Bone-derived biochar improved soil quality and reduced Cd and Zn phytoavailability in a multi-metal contaminated mining soil

Reusing by-products such as cow bones in agriculture can be achieved thorough pyrolysis. The potential of bone-derived biochar as a promising material for metals immobilization in contaminated mining soils has not yet been sufficiently explored. Therefore, cow bones were used as biochar feedstock were pyrolyzed at 500 °C (CBL) and 800 °C (CBH) and. The two biochars were applied to a mine contaminated soil at 0 (control), 2.5, 5 and 10%, w/w, dosages; then, the soils were incubated and cultivated by maize in the greenhouse. Cadmium (Cd) and zinc (Zn) bioavailability and their sequentially extracted fractions (acid soluble, reducible, oxidizable, and residual fraction), soil microbial function, and plant health attributes were analyzed after maize harvesting. Bone-derived biochar enhanced the content of dissolved organic carbon (up to 74%), total nitrogen (up to 26%), and total phosphorus (up to 27%) in the soil and improved the plant growth up to 55%, as compared to the control. The addition of CBL altered the acid soluble fraction of both metals to the residual fraction and, thus, reduced the content of Zn (55 and 40%) and Cd (57 and 67%) in the maize roots and shoots, respectively as compared to the control. The CBL enhanced the β-glucosidase (51%) and alkaline phosphatase activities (71%) at the lower doses (2.5-5%) as compared to control, while the activities of these enzymes decreased with the higher application doses. Also, CBL improved the antioxidants activity and maize growth at the 2.5-5% application rate. However, the activity of the dehydrogenase significantly decreased (77%), particularly with CBH. We conclude that CBL, applied at 2.5-5% dose, can be utilized as a potential low cost and environmental friendly amendment for stabilization of toxic metals in contaminated mining soils and producing food/feed/biofuel crops with lower metal content.