Pearl millet growth and biochemical alterations determined by mycorrhizal inoculation, water availability and atmospheric CO2 concentration

Pearl millet (Pennisetum glaucum L.) is an important fodder and is a potential feedstock for fuel ethanol production in dry areas. Our objectives were to assess the effect of elevated CO2 and/or reduced irrigation on biomass production and levels of sugars and proteins in leaves of pearl millet and to test whether mycorrhizal inoculation could modulate the effects of these abiotic factors on growth and metabolism. Results showed that mycorrhizal inoculation and water regime most influenced biomass of shoots and roots; however, their individual effects were dependent on the atmospheric CO2 concentration. At ambient CO2, mycorrhizal inoculation helped to alleviate effects of water deficit on pearl millet without significant decreases in biomass production, which contrasted with the low biomass of mycorrhizal plants under restricted irrigation and elevated CO2. Mycorrhizal inoculation enhanced water content in shoots, whereas reduced irrigation decreased water content in roots. The triple interaction between CO2, arbuscular mycorrhizal fungi (AMF) and water regime significantly affected the total amount of soluble sugars and determined the predominant soluble sugars in leaves. Under optimal irrigation, elevated CO2 increased the proportion of hexoses in pearl millet that was not inoculated with AMF, thus improving the quality of this plant material for bioethanol production. By contrast, elevated CO2 decreased the levels of proteins in leaves, thus limiting the quality of pearl millet as fodder and primary source for cattle feed.This study has been supported by the ‘Ministerio de Ciencia e Innovación’ and ‘Gobierno de Aragón’ (Spain) (BFU2011-26989, Group A-44). Eliseu Geraldo dos Santos Fabbrin received a grant from CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) from the Brazilian Government

Nutritional quality and yield of onion as affected by different application methods and doses of humic substances

Fertilization with humic substances (HS) has been proposed as target tool to improve crop production within a sustainable agriculture framework. The dose and application method are two factors that can influence the effect of HS on nutrient composition and productivity of onion. Therefore, our main objective was to assess the effect of each of the abovementioned factors, separately or interacting, on the quality and productivity of onion bulbs in a field test. The experimental design was completely randomized in a factorial 2 × 3, with two methods of application of HS and three different doses. The combined application method, immersion together with foliar pulverization, showed highest improvement of biomass and nutritional content of bulbs. However, while the intermediate dose of HS exerted greater increases on onion yield, productivity, carbohydrates and proteins levels in bulbs, mineral nutrient accumulation resulted especially when highest doses of HS were added. From a nutritional point of view, higher sweetness (from 113 to 149 mg g−1 of soluble sugars in dry matter) and an improved P, K and Mg content of bulbs (4.00, 11.65 and 3.18 g kg−1, respectively) in response to HS addition has been ascribed.Marcelle M. Bettoni received a grant from ‘Los CAPES y Coordenação do Programa de Pós-graduação em Agronomia–Produção Vegetal’ from the Brazilian Government

Pearl millet growth and biochemical alterations determined by mycorrhizal inoculation, water availability and atmospheric CO2 concentration

Pearl millet (Pennisetum glaucum L.) is an important fodder and is a potential feedstock for fuel ethanol production in dry areas. Our objectives were to assess the effect of elevated CO2 and/or reduced irrigation on biomass production and levels of sugars and proteins in leaves of pearl millet and to test whether mycorrhizal inoculation could modulate the effects of these abiotic factors on growth and metabolism. Results showed that mycorrhizal inoculation and water regime most influenced biomass of shoots and roots; however, their individual effects were dependent on the atmospheric CO2 concentration. At ambient CO2, mycorrhizal inoculation helped to alleviate effects of water deficit on pearl millet without significant decreases in biomass production, which contrasted with the low biomass of mycorrhizal plants under restricted irrigation and elevated CO2. Mycorrhizal inoculation enhanced water content in shoots, whereas reduced irrigation decreased water content in roots. The triple interaction between CO2, arbuscular mycorrhizal fungi (AMF) and water regime significantly affected the total amount of soluble sugars and determined the predominant soluble sugars in leaves. Under optimal irrigation, elevated CO2 increased the proportion of hexoses in pearl millet that was not inoculated with AMF, thus improving the quality of this plant material for bioethanol production. By contrast, elevated CO2 decreased the levels of proteins in leaves, thus limiting the quality of pearl millet as fodder and primary source for cattle feed

Growth and metabolism of onion seedlings as affected by the application of humic substances, mycorrhizal inoculation and elevated CO2

© 2014 Elsevier B.V. Onion (Allium cepa L.) is a crop with great economic importance over the world. The vigor of seedlings plays a crucial role in the posterior growth and quality of bulbs. Application of humic substances (HS), inoculation of arbuscular mycorrhizal fungi (AMF) in the soil and enhancement of atmospheric CO2 are three factors that can influence plant growth and development. Therefore, our main objective was to assess the effect of each of the abovementioned factors, separately or interacting, on the metabolism and growth of onion seedlings before bulb formation and under greenhouse conditions. Results showed that these three factors appear as valid horticultural techniques for improving growth and quality of onion seedlings cultivated in greenhouse even when mycorrhizal colonization of roots does not achieve high rates. Beneficial effects of HS were additive to those of mycorrhizal inoculation or elevated CO2 (ECO2) on shoot and root biomass production. The triple interaction between exogenous HS application, mycorrhizal inoculation and ECO2 induced the highest accumulation of soluble sugars, proteins and proline in leaves, suggesting that such interaction was the most effective for increasing the quality of onion shoots as source organs for posterior growth and quality of bulbs and also for enhancing the tolerance of onion seedlings to environmental stresses.This study has been supported by the Ministerio de Economía y Competitividad (MINECO) from Gobierno de España (Spain)(BFU 2011-26989). Marcelle M. Bettoni received a grant from ‘Los CAPES y Coordenação do Programa de Pós-graduação em Agronomia–Produção Vegetal’ from the Brazilian Government.Peer Reviewe

The interaction between mycorrhizal inoculation, humic acids supply and elevated atmospheric CO2 increases energetic and antioxidant properties and sweetness of yellow onion

The combined application of humic substances and mycorrhizal inocula under increased CO in the air is a promising horticultural technique for improving the quality of greenhouse-grown onion seedlings. The objective of this study was to evaluate if the development and qualitative characteristics of bulbs from the yellow onion Allium cepa L. Alfa São Francisco improved with the application of the abovementioned agronomic, biotic, and environmental factors. The lowest dry matter was achieved in bulbs of onions not inoculated with mycorrhizal fungi, non-amended with humic acids (HA), and grown at ambient CO. Mycorrhizal inoculation significantly increased bulb biomass in plants cultivated at ambient CO, and not fertilized with HA, which may be a consequence of the enhanced acid phosphatase activity in roots. The application of HA always increased bulb dry matter, which were more evident at elevated rather than ambient CO conditions and correlated with improved acid phosphatase activity in the plants at elevated CO. Mycorrhizal inoculation, HA supplementation, and elevated CO in the air had an additive effect of increasing the content of soluble sugars, proteins, and phenolics in bulbs. While high levels of sugars and proteins enhanced the energetic value of onions, the increase in phenolics improved their antioxidant properties. The triple interaction between mycorrhization, HA fertilization, and elevated CO also increased the ratio between soluble solids and total titratable acidity, which may enhance the perception of sweetness and make onions more pleasant for consumption.This study has been supported by the ‘Ministerio de Ciencia e Innovación’ (Spain) (BFU2011-26989). Marcelle M. Bettoni received a grant from ‘Los CAPES y Coordenação do Programa de Pós-graduação em Agronomia - Produção Vegetal’ from the Brazilian Government.Peer reviewe