Future CO2 , warming and water deficit impact white and red Tempranillo grapevine: Photosynthetic acclimation to elevated CO2 and biomass allocation

Assessing the growth dynamics of alfalfa varieties (Medicago sativa cv. Bilensoy 80 and Nimet) response to varied carbon dioxide (CO2) concentrations

Rising atmospheric CO2 levels drive greenhouse effects, elevating temperatures, and diminishing water accessibility in semi-arid regions, affecting agriculture. Alfalfa contributes to climate change mitigation by sequestering carbon, enhancing soil fertility and carbon storage, reducing synthetic nitrogen fertilizer use, preventing soil erosion, supplying high-quality livestock feed, and serving as a bioenergy source. This research examined the effects of elevated CO2 levels in climate change scenarios (600, 800, and 1000 ppm, with control at 400 ppm) on two alfalfa varieties, Medicago sativa cv. Nimet and Bilensoy-80. The experiments were conducted in specialized Climate Change Simulation Greenhouses, allowing control of CO2, water, and temperature variables. Results revealed a positive relationship between higher CO2 concentrations and increased photosynthesis (P ≤ 0.001), promoting the plant growth leaf area (P ≤ 0.001), yields and both leaf (P ≤ 0.05) and stem dry biomass (P ≤ 0.001). At 1000 ppm CO2, a saturation point was reached, halting further photosynthesis. This down-regulation was linked to decreased intercellular CO2 levels, which expedited chlorophyll and breakdown and potentially induced leaf senescence. High CO2 levels led to greater biomass, as anticipated. However, total protein levels, a forage quality indicator, initially decreased with high CO2 concentrations (up to 1000 ppm) due to an inverse relationship with shoot yield. Surprisingly, the 1000 ppm CO2 concentration mitigated this protein reduction in both alfalfa varieties.

Global warming changes biomass and C:N:P stoichiometry of different components in terrestrial ecosystems

Global warming has significantly affected terrestrial ecosystems. Biomass and C:N:P stoichiometry of plants and soil is crucial for enhancing plant productivity, improving human nutrition, and regulating biogeochemical cycles. However, the effect of warming on the biomass and C:N:P stoichiometry of different components (plant, leaf, stem, root, litter, soil, and microbial biomass) in various terrestrial ecosystems remains uncertain. We conducted a comprehensive meta-analysis to investigate the global patterns of biomass and C:N:P stoichiometry responses to warming, as well as interaction relationships based on 1399 paired observations from 105 warming studies. Results indicated that warming had a significant impact on various aspects of plant growth, including an increase in plant biomass (+16.55%), plant C:N ratio (+4.15%), leaf biomass (+16.78%), stem biomass (+23.65%), root biomass (+22.00%), litter C:N ratio (+9.54%) and soil C:N ratio (+5.64%). However, it also decreased stem C:P ratio (-23.34%), root C:P ratio (-12.88%), soil N:P ratio (-14.43%) and soil C:P ratio (-16.33%). The magnitude of warming was the primary drivers of changes of biomass and C:N:P stoichiometry. By establishing the general response curves of changes in biomass and C:N:P ratios with increasing temperature, we demonstrated that warming effect on plant, root, and litter biomass shifted from negative to positive, whereas that on leaf and stem biomass changed from positive to negative as temperature increased. Additionally, the effect of warming on root C:N ratio, root biomass, and microbial biomass N:P ratios shifted from positive to negative, whereas the effects on plant N:P, leaf N:P, leaf C:P, root N:P ratios, and microbial biomass C:N ratio changed from negative to positive with increasing temperature. Our research can help assess plant productivity and optimize ecosystem stoichiometry precisely in the context of global warming.

Elevated CO2 may increase the health risks of consuming leafy vegetables cultivated in flooded soils contaminated with Cd and Pb

Elevated CO₂ levels threat the crop quality by altering the environmental behavior of heavy metals (HMs) in soils. In reality, multiple HMs often co-exist in field, while details regarding coexisting HMs migration in flooded soil at elevated CO₂ levels remain unclear. A pot experiment in open-top chambers (CO₂ at 400 and 600 μmol mol^-1) was conducted to explore the uptake and transfer of cadmium (Cd) and lead (Pb) in water dropwort (Oenanthe javanica DC.) grown in flooded soils contaminated with Cd and Pb. Results showed that elevated CO₂ significantly reduced soil pH, promoting the release of Cd and Pb (by 63.64-106.90% and 10.66-30.99%, respectively) into soil porewater. In the harvested O. javanica, elevated CO₂ decreased the root uptake of Cd but promoted that of Pb. Further mechanism analysis showed that elevated CO₂ promoted the formation of iron plaque on root surface by 44.60-139.57%, with lower adsorption capacity to HMs (0-34.93% and 63.61-67.69% for Cd and Pb, respectively). Meanwhile, Pb showed lower adsorbability in iron plaque but higher transfer capacity when compared with Cd. Ultimately, elevated CO₂ increased the target hazard quotient values of Pb in O. javanica. These findings provide new insights on the effects of elevated CO₂ on the transfer of coexisting HMs in soil-plant system, and the risk of HMs pollution under climate changes needs to be more fully assessed.

Is Tempranillo Blanco Grapevine Different from Tempranillo Tinto Only in the Color of the Grapes? An Updated Review

Tempranillo Blanco is a somatic variant of Tempranillo Tinto that appeared as a natural, spontaneous mutation in 1988 in a single shoot of a single plant in an old vineyard. It was vegetatively propagated, and currently wines from Tempranillo Blanco are commercially available. The mutation that originated Tempranillo Blanco comprised single-nucleotide variations, chromosomal deletions, and reorganizations, losing hundreds of genes and putatively affecting the functioning and regulation of many others. The most evident, visual change in Tempranillo Blanco is the anthocyanin lost, producing this grapevine variety bunches of colorless grapes. This review aims to summarize from the available literature differences found between Tempranillo Blanco and Tinto in addition to the color of the grapes, in a climate change context and using fruit-bearing cuttings grown in temperature-gradient greenhouses as research-oriented greenhouses. The differences found include changes in growth, water use, bunch mass, grape quality (both technological and phenolic maturity), and some aspects of their photosynthetic response when grown in an atmosphere of elevated CO2 concentration and temperature, and low water availability. Under field conditions, Tempranillo Blanco yields less than Tempranillo Tinto, the lower weight of their bunches being related to a lower pollen viability and berry and seed setting.

Acclimation to elevated CO2 affects the C/N balance by reducing de novo N-assimilation

Plants exposed to elevated atmospheric CO₂ concentrations show an increased photosynthetic activity. However, after prolonged exposure, the activity declines. This acclimation to elevated CO₂ is accompanied by a rise in the carbon-to-nitrogen ratio of the biomass. Hence, increased sugar accumulation and sequential downregulation of photosynthetic genes, as well as nitrogen depletion and reduced protein content, have been hypothesized as the cause of low photosynthetic performance. However, the reason for reduced nitrogen content in plants at high CO₂ is unclear. Here, we show that reduced photorespiration at increased CO₂ -to-O₂ ratio leads to reduced de novo assimilation of nitrate, thus shifting the C/N balance. Metabolic modeling of acclimated and non-acclimated plants revealed the photorespiratory pathway to function as a sink for already assimilated nitrogen during the light period, providing carbon skeletons for de novo assimilation. At high CO₂ , low photorespiratory activity resulted in diminished nitrogen assimilation and eventually resulted in reduced carbon assimilation. For the hpr1-1 mutant, defective in reduction of hydroxy-pyruvate, metabolic simulations show that turnover of photorespiratory metabolites is expanded into the night. Comparison of simulations for hpr1-1 with those for the wild type allowed investigating the effect of a perturbed photorespiration on N-assimilation.

Water Deficit Modulates the CO2 Fertilization Effect on Plant Gas Exchange and Leaf-Level Water Use Efficiency: A Meta-Analysis

Elevated atmospheric CO2 concentrations ([eCO2]) and soil water deficits significantly influence gas exchange in plant leaves, affecting the carbon-water cycle in terrestrial ecosystems. However, it remains unclear how the soil water deficit modulates the plant CO2 fertilization effect, especially for gas exchange and leaf-level water use efficiency (WUE). Here, we synthesized a comprehensive dataset including 554 observations from 54 individual studies and quantified the responses for leaf gas exchange induced by e[CO2] under water deficit. Moreover, we investigated the contribution of plant net photosynthesis rate (P n ) and transpiration rates (T r) toward WUE in water deficit conditions and e[CO2] using graphical vector analysis (GVA). In summary, e[CO2] significantly increased P n and WUE by 11.9 and 29.3% under well-watered conditions, respectively, whereas the interaction of water deficit and e[CO2] slightly decreased P n by 8.3%. Plants grown under light in an open environment were stimulated to a greater degree compared with plants grown under a lamp in a closed environment. Meanwhile, water deficit reduced P n by 40.5 and 37.8%, while increasing WUE by 24.5 and 21.5% under ambient CO2 concentration (a[CO2]) and e[CO2], respectively. The e[CO2]-induced stimulation of WUE was attributed to the common effect of P n and T r, whereas a water deficit induced increase in WUE was linked to the decrease in T r. These results suggested that water deficit lowered the stimulation of e[CO2] induced in plants. Therefore, fumigation conditions that closely mimic field conditions and multi-factorial experiments such as water availability are needed to predict the response of plants to future climate change.

Assessment of Nutritional and Quality Properties of Leaves and Musts in Three Local Spanish Grapevine Varieties Undergoing Controlled Climate Change Scenarios

The market demand together with the need for alternatives to withstand climate change led to the recovery of autochthonous grapevine varieties. Under climate change, the summer pruning of vineyards may lead to an increase of vegetative residuals of nutritional and medicinal interest. The objectives of our study were (1) to evaluate the nutritional properties of the leaves of three local Spanish grapevines (Tinto Velasco, TV, Pasera, PAS, and Ambrosina, AMB) when grown under climate change conditions, and (2) to test the potentiality of these grapevines as suitable candidates to be cultivated under climate change scenarios based on the quality of their must. Experimental assays were performed with fruit-bearing cuttings grown in temperature gradient greenhouses that simulate rising CO₂ (700 μmol mol^-1) and warming (ambient temperature +4 °C), either acting alone or in combination. TV and AMB were the most and the least affected by air temperature and CO₂ concentration, respectively. The interaction of elevated CO₂ with high temperature induced the accumulation of proteins and phenolic compounds in leaves of TV, thus enhancing their nutritional properties. In PAS, the negative effect of high temperature on protein contents was compensated for by elevated CO₂. Warming was the most threatening scenario for maintaining the must quality in the three varieties, but elevated CO₂ exerted a beneficial effect when acting alone and compensated for the negative effects of high temperatures. While TV may be a candidate to be cultivated in not very warm areas (higher altitudes or colder latitudes), PAS behaved as the most stable genotype under different environmental scenarios, making it the most versatile candidate for cultivation in areas affected by climate change.