Elevated and super-elevated CO2 differ in their interactive effects with nitrogen availability on fruit yield and quality of cucumber

Feeding the world: impacts of elevated [CO2] on nutrient content of greenhouse grown fruit crops and options for future yield gains

Several long-term studies have provided strong support demonstrating that growing crops under elevated [CO2] can increase photosynthesis and result in an increase in yield, flavour and nutritional content (including but not limited to Vitamins C, E and pro-vitamin A). In the case of tomato, increases in yield by as much as 80% are observed when plants are cultivated at 1000 ppm [CO2], which is consistent with current commercial greenhouse production methods in the tomato fruit industry. These results provide a clear demonstration of the potential for elevating [CO2] for improving yield and quality in greenhouse crops. The major focus of this review is to bring together 50 years of observations evaluating the impact of elevated [CO2] on fruit yield and fruit nutritional quality. In the final section, we consider the need to engineer improvements to photosynthesis and nitrogen assimilation to allow plants to take greater advantage of elevated CO2 growth conditions.

China’s Socioeconomic and CO2 Status Concerning Future Land-Use Change under the Shared Socioeconomic Pathways

China has experienced a huge socioeconomic advancement over the past few decades, resulting in great change in land use and land cover. To date, negligible attention has been given to examining the socioeconomic changes in the context of land-use change, especially from a futuristic standpoint. However, motivated by China’s latest carbon neutrality target, this study analyzes the prospective changes in socioeconomic status, and carbon dioxide emission in the context of future land-use change, focusing on three future periods: 2026–2030 (carbon dioxide peak phase), 2056–2060 (carbon-neutral phase), and 2080–2099 (long-term period). In this regard, recently published land-use products under seven Shared Socioeconomic Pathways-based scenarios (SSP1-1.9, SSP1-2.6, SSP4-3.4, SSP2-4.5, SSP4-6.0, SSP3-7.0, and SSP5-8.5) as part of the CMIP6, as well as the projected GDP and population under five socioeconomic scenarios are used. To estimate socioeconomic change over prominent land-use types (urban), we combined five socioeconomic scenarios with seven corresponding SSPs-based land-use change scenarios (SSP1 with SSP1-1.9 and SSP1-2.6; SSP2 with SSP2-4.5; SSP3 with SSP3-7.0; SSP4 with SSP4-3.4 and SSP4-6.0; and SSP5 with SSP5-8.5 scenarios). Our results reveal that rapid urban land expansion in the future is the most dominant aspect in China. In the carbon neutrality phase (2056–2060), urban land is expected to expand ~80% more than that of the reference period (1995–2014). In the spatial aspect, the expansion of urban land is mainly prominent in the eastern and central parts of China. For socioeconomic changes, the most prominent increase in the urban population is estimated at 630.8% under SSP5-8.5 for the 2056–2060 period compared to the reference period. Regarding GDP for the urban area, industrial GDP will be higher than service GDP in the carbon emission peak phase (2026–2030), but it is projected to be overtaken by service GDP for the carbon-neutral target (2056–2060) and long-term periods (2080–2099). Further, the CO2 emission in China was found to increase with intensified urban land for the historical period (1995–2019). In the future, the largest increase in CO2 emission from the urban area is anticipated under SSP5-8.5 in the carbon-neutral target (2056–2060) phase, while CO2 emission will largely decline after (2056–2060) under SSP1-1.9, SSP1-2.6, and SSP4-3.4. Importantly, population change is expected to be the most predominant factor in future urban land expansion in China. These findings highlight the importance of well-governed urban-land development as a key measure to achieve China’s carbon neutrality goal.

The Potential Impact of Climate Change on the Micronutrient-Rich Food Supply

Micronutrient deficiencies are a major cause of morbidity and mortality in low- and middle-income countries worldwide. Climate change, characterized by increasing global surface temperatures and alterations in rainfall, has the capacity to affect the quality and accessibility of micronutrient-rich foods. The goals of this review are to summarize the potential effects of climate change and its consequences on agricultural yield and micronutrient quality, primarily zinc, iron, and vitamin A, of plant foods and upon the availability of animal foods, to discuss the implications for micronutrient deficiencies in the future, and to present possible mitigation and adaptive strategies. In general, the combination of increasing atmospheric carbon dioxide and rising temperature is predicted to reduce the overall yield of major staple crops, fruits, vegetables, and nuts, more than altering their micronutrient content. Crop yield is also reduced by elevated ground-level ozone and increased extreme weather events. Pollinator loss is expected to reduce the yield of many pollinator-dependent crops such as fruits, vegetables, and nuts. Sea-level rise resulting from melting of ice sheets and glaciers is predicted to result in coastal inundation, salt intrusion, and loss of coral reefs and mangrove forests, with an adverse impact upon coastal rice production and coastal fisheries. Global ocean fisheries catch is predicted to decline because of ocean warming and declining oxygen. Freshwater warming is also expected to alter ecosystems and reduce inland fisheries catch. In addition to limiting greenhouse gas production, adaptive strategies include postharvest fortification of foods; micronutrient supplementation; biofortification of staple crops with zinc and iron; plant breeding or genetic approaches to increase zinc, iron, and provitamin A carotenoid content of plant foods; and developing staple crops that are tolerant of abiotic stressors such as elevated carbon dioxide, elevated temperature, and increased soil salinity.

Nitrogen management under increased atmospheric CO2 concentration in cucumber (Cucumis sativus L.): ameliorating environmental impacts of fertilization

In the last years, the atmospheric CO2 concentration has increased significantly, and this increase can cause changes in various physiological and biochemical processes of plants. However, the response of plants to elevated CO2 concentration (e[CO2]) will be different depending on the nitrogen form available and the plant species. Therefore, hydroponic trials on cucumber plants, with two CO2 concentrations (400 and 1000 ppm) and two nitrogen sources (NO3-/NH4+; 100/0 and 90/10), were conducted. Physiological parameters-such as gas exchange, GS, GOGAT and GDH activities, cation composition, soluble sugar and starch content- were measured. The results showed that when plants were grown with NH4+ and e[CO2], parameters such as photosynthesis rate (ACO2), instantaneous water use efficiency (WUEi), the content of NH4+, Ca2+ and Mg2+, and the concentration of starch, were higher than in control plants (irrigated with nitrate as sole nitrogen source and ambient CO2 concentration (a[CO2])). Furthermore, an improvement in N assimilation was observed when the GS/GOGAT pathway was enhanced under these conditions (NH4+ and e[CO2]). Thus, our results contribute to the reduction of the negative environmental impacts of the use of nitrogen fertilizers on this crop, both by reducing nitrogen leakage (eutrophication) and greenhouse gas emissions.

Short Term Elevated CO2 Interacts with Iron Deficiency, Further Repressing Growth, Photosynthesis and Mineral Accumulation in Soybean (Glycine max L.) and Common Bean (Phaseolus vulgaris L.)

Elevated CO2 (eCO2) has been reported to cause mineral losses in several important food crops such as soybean (Glycine max L.) and common bean (Phaseolus vulgaris L.). In addition, more than 30% of the world’s arable land is calcareous, leading to iron (Fe) deficiency chlorosis and lower Fe levels in plant tissues. We hypothesize that there will be combinatorial effects of eCO2 and Fe deficiency on the mineral dynamics of these crops at a morphological, biochemical and physiological level. To test this hypothesis, plants were grown hydroponically under Fe sufficiency (20 μM Fe-EDDHA) or deficiency (0 μM Fe-EDDHA) at ambient CO2 (aCO2, 400 ppm) or eCO2 (800 ppm). Plants of both species exposed to eCO2 and Fe deficiency showed the lowest biomass accumulation and the lowest root: shoot ratio. Soybean at eCO2 had significantly higher chlorophyll levels (81%, p < 0.0001) and common bean had significantly higher photosynthetic rates (60%, p < 0.05) but only under Fe sufficiency. In addition, eCO2 increased ferric chelate reductase acivity (FCR) in Fe-sufficient soybean by 4-fold (p < 0.1) and in Fe-deficient common bean plants by 10-fold (p < 0.0001). In common bean, an interactive effect of both environmental factors was observed, resulting in the lowest root Fe levels. The lowering of Fe accumulation in both crops under eCO2 may be linked to the low root citrate accumulation in these plants when grown with unrestricted Fe supply. No changes were observed for malate in soybean, but in common bean, shoot levels were significantly lower under Fe deficiency (77%, p < 0.05) and Fe sufficiency (98%, p < 0.001). These results suggest that the mechanisms involved in reduced Fe accumulation caused by eCO2 and Fe deficiency may not be independent, and an interaction of these factors may lead to further reduced Fe levels.

Drip fertigation with straw incorporation significantly reduces N2O emission and N leaching while maintaining high vegetable yields in solar greenhouse production

Approximately 1/3 of vegetables in China are produced in solar greenhouses. Most farmers use conventional irrigation with over fertilisation (CIF), thereby applying approximately 2000 kg N ha-1 fertiliser over two cropping seasons per year. Here, we tested the effect of drip irrigation with reduced fertilisation (DIF) combined with straw incorporation on reducing N2O emissions and nitrogen leaching from solar greenhouse vegetable production systems. Over three consecutive tomato cropping seasons, N2O emissions and nitrogen leaching were monitored in high temporal resolution, thereby producing a unique dataset. Compared to CIF, the realised drip fertigation scheme reduces N2O emission and nitrogen leaching of nitrate and dissolved organic nitrogen by approximately a factor of 5-10 (N2O-DIF: 10.3, CIF: 47.5 kg N ha-1 yr-1; N leaching-DIF: 83.6, CIF: 863 kg N ha-1 yr-1). Straw incorporation in CIF, though advantageous for soil health, resulted in pollution swapping as soil N2O emissions increased while NO3- leaching losses decreased. On the contrary, no significant negative environmental N effects of straw incorporation were found for DIF. As crop productivity was not affected by straw incorporation, neither for CIF nor for DIF, our study provides a sound basis for policy advice to recommend farmers to adopt drip fertigation combined with straw application. Wide scale adoption of this technique will result in reductions of environment N losses, alleviate major soil degradation signs, including soil acidity, nutrient imbalance and deterioration of soil microbial community structure, while allowing to maintaining high yields of vegetables in solar greenhouse production systems.

The Formation of Fruit Quality in Cucumis sativus L

Cucumber is one of the most widely grown vegetables in China and an indispensable fresh fruit in the diet. With the development of society, the demand of people for cucumber quality is higher and higher. Therefore, cultivating high-quality cucumber varieties is one of the main goals of cucumber breeding. With the rapid development of biotechnology such as molecular marker, cucumber quality control network is becoming clear. In this review, we describe the formation mechanism of cucumber fruit quality from three aspects: (1) the commercial quality of cucumber fruit, (2) nutritional quality formation, and (3) flavor quality of cucumber fruit. In addition, the determinants of cucumber fruit quality were summarized from two aspects of genetic regulation and cultivation methods in order to provide ideas for cucumber researchers and cultivators to improve fruit quality.

Transcutaneous carbon dioxide measurements in fruits, vegetables and humans: A prospective observational study

BACKGROUND

Transcutaneous carbon dioxide measurement (TcCO2) is frequently used as a surrogate for arterial blood gas sampling in adults and children with critical illness. Data from noninvasive TcCO2 monitoring assists with clinical decisions regarding mechanical ventilation settings, estimation of metabolic consumption and determination of adequate end-organ tissue perfusion.

OBJECTIVES

To report TcCO2 values obtained from various fruits, vegetables and elite critical care medicine specialists.

DESIGN

Prospective, observational, nonblinded cohort study.

SETTINGS

Single-centre, tertiary paediatric referral centre and organic farmers' market.

PARTICIPANTS

Vegetables and fruits included 10 samples of each of the following: red delicious apple (Malus domestica), manzano banana (Musa sapientum), key lime (Citrus aurantiifolia), miniature sweet bell pepper (Capsicum annuum), sweet potato (Ipomoea batatas) and avocado (Persea americana). Ten human controls were studied including a paediatric intensivist, a paediatric inpatient hospital physician, four paediatric resident physicians and four paediatric critical care nurses.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

TcCO2 values for each species and device response times.

RESULTS

TcCO2 readings were measurable in all study species except the sweet potato. Mean ± SD values of TcCO2 for human controls [4.34 ± 0.37 kPa (32.6 ± 2.8 mmHg)] were greater than apples [3.09 ± 0.19 kPa (23.2 ± 1.4 mmHg), P < 0.01], bananas [2.73 ± 0.28 kPa (20.5 ± 2.1 mmHg), P < 0.01] and limes [2.76 ± 0.52 kPa (20.7 ± 3.9 mmHg), P < 0.01] but no different to those of avocados [4.29 ± 0.44 kPa (32.2 ± 3.3 mmHg), P = 0.77] and bell peppers [4.19 ± 1.13 kPa (31.4 ± 8.5 mmHg), P = 0.68]. Transcutaneous response times did not differ between research cohorts and human controls.

CONCLUSION

We found nonroot, nontuberous vegetables to have TcCO2 values similar to that of healthy, human controls. Fruits yield TcCO2 readings, but substantially lower than human controls.

Interactive Effects of the CO2 Enrichment and Nitrogen Supply on the Biomass Accumulation, Gas Exchange Properties, and Mineral Elements Concentrations in Cucumber Plants at Different Growth Stages

The concentration changes of mineral elements in plants at different CO2 concentrations ([CO2]) and nitrogen (N) supplies and the mechanisms which control such changes are not clear. Hydroponic trials on cucumber plants with three [CO2] (400, 625, and 1200 μmol mol−1) and five N supply levels (2, 4, 7, 14, and 21 mmol L−1) were conducted. When plants were in high N supply, the increase in total biomass by elevated [CO2] was 51.7% and 70.1% at the seedling and initial fruiting stages, respectively. An increase in net photosynthetic rate (Pn) by more than 60%, a decrease in stomatal conductance (Gs) by 21.2–27.7%, and a decrease in transpiration rate (Tr) by 22.9–31.9% under elevated [CO2] were also observed. High N supplies could further improve the Pn and offset the decrease of Gs and Tr by elevated [CO2]. According to the mineral concentrations and the correlation results, we concluded the main factors affecting these changes. The dilution effect was the main factor driving the reduction of all mineral elements, whereas Tr also had a great impact on the decrease of [N], [K], [Ca], and [Mg] except [P]. In addition, the demand changes of N, Ca, and Mg influenced the corresponding element concentrations in cucumber plants.

Nitrogen Fertilizer Levels Affect the Growth and Quality Parameters of Astragalus mongolica

Owing to overexploitation, wild resources of Astragalus mongolica, a Chinese herbal plant that is widely distributed in the arid and semi-arid areas of Northern China, have gradually become exhausted, and therefore, commercial cultivation is increasingly important to meet the growing demand for astragalus and reduce the pressure on wild populations. Nitrogen level is an important factor that affects the yield and quality of A. mongolica. However, uniform standards for fertilization among production areas have not yet been determined. In this study, the effect of nitrogen fertilizer treatment on the yield and quality of A. mongolica in the Qinghai-Tibet Plateau was explored using a control treatment (no added nitrogen, N0) and five different nutrient levels: 37.5 kg/ha (N1), 75 kg/ha (N2), 112.5 kg/ha (N3), 150 kg/ha (N4), and 187.5 kg/ha (N5). According to grey relational analysis, the optimal nitrogen fertilizer treatment was the N4 level followed by the N5 and N2 levels. Nitrogen fertilizer significantly increased the root biomass, plant height, root length, and root diameter. However, nitrogen fertilization had no significant effect on the content of Astragaloside IV and mullein isoflavone glucoside. The content of ononin and calycosin continually accumulated throughout the growing period. The results showed that the ononin and calycosin content under N4 and N2 is higher than other levels and there is not significantly different between different nitrogen fertilizer levels about them. The content of formononetin decreased gradually with the progression of the growing season. The optimal nitrogen fertilizer treatment for A. mongolica is recommended to be 150 kg/ha and the content of active compounds and yield were observed to reach the maximum in October.

Effects of Elevated CO2 on Nutritional Quality of Vegetables: A Review

Elevated atmospheric CO2 (eCO2) enhances the yield of vegetables and could also affect their nutritional quality. We conducted a meta-analysis using 57 articles consisting of 1,015 observations and found that eCO2 increased the concentrations of fructose, glucose, total soluble sugar, total antioxidant capacity, total phenols, total flavonoids, ascorbic acid, and calcium in the edible part of vegetables by 14.2%, 13.2%, 17.5%, 59.0%, 8.9%, 45.5%, 9.5%, and 8.2%, respectively, but decreased the concentrations of protein, nitrate, magnesium, iron, and zinc by 9.5%, 18.0%, 9.2%, 16.0%, and 9.4%. The concentrations of titratable acidity, total chlorophyll, carotenoids, lycopene, anthocyanins, phosphorus, potassium, sulfur, copper, and manganese were not affected by eCO2. Furthermore, we propose several approaches to improving vegetable quality based on the interaction of eCO2 with various factors, including species, cultivars, CO2 levels, growth stages, light, O3 stress, nutrient, and salinity. Finally, we present a summary of the eCO2 impact on the quality of three widely cultivated crops, namely, lettuce, tomato, and potato.