Comportamento fisio-bioquímico da soja em resposta ao encharcamento do solo associado ao excesso de ferro
Carregando...
Data
2019-12-17
Autores
Lapaz, Allan de Marcos
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O encharcamento do solo é um problema comum em algumas áreas agricultáveis, inclusive em regiões sob cultivo de soja (Glycine max). Em solos encharcados, ocorre a depleção de O2 do solo pelos microrganismos aeróbicos e plantas, afetando os processos metabólicos e fisiológicos das plantas após sofrerem anoxia no tecido radicular. Outro fator prejudicial neste contexto, é o aumento exponencial da disponibilidade de ferro (Fe) no solo, o que pode resultar na absorção excessiva do Fe pelas plantas. No primeiro experimento, o objetivo foi avaliar a vulnerabilidade do aparato fotossintético e produção de biomassa de duas cultivares de soja no estágio fenológico V2, sob condição hídrica adequada e diferentes níveis de encharcamento do solo associada a uma concentração moderada e duas concentrações tóxicas de Fe. No segundo experimento, o objetivo foi avaliar o comportamento fisiológico e bioquímico da soja cultivar Agroeste 3680 associado ao desenvolvimento das vagens (estágio fenológico R3) sob solo não encharcado e encharcado combinado com uma concentração moderada e duas concentrações tóxicas de Fe. No primeiro experimento, o aparato fotossintético das cultivares de soja responderam diferentemente ao encharcamento e à disponibilidade de Fe no solo. Ambas cultivares foram vulneráveis ao encharcamento de 100% em todas as concentrações Fe, o que resultou em danos acentuados às trocas gasosas, concentração de clorofilas e, consequentemente, levou à diminuição da biomassa seca da parte aérea e da raiz. O desempenho fotossintético e a produção de biomassa seca do Agroeste 3680 não foram afetados quando expostos a concentrações moderadas de Fe associadas ao encharcamento de 50%. A cultivar NS 6601 IPRO apresentou tolerância moderada ao Fe quando não cultivada em solo encharcado, uma vez que a taxa de assimilação de CO2, a eficiência instantânea da carboxilação e a concentração da clorofila a não foram afetadas. No segundo experimento, as trocas gasosas foram fortemente afetadas pelo encharcamento do solo. O excesso de Fe sem encharcamento do solo reduziu os pigmentos fotossintéticos e potencializou a redução quando associado ao encharcamento do solo. O acúmulo de amido e ureídeos no primeiro trifólio totalmente expandido podem ser considerados biomarcadores eficientes para indicar a fitotoxicidade causada pelo encharcamento do solo e excesso de Fe em plantas de soja. O comportamento da biomassa seca das vagens revelou que o desenvolvimento reprodutivo é bruscamente interrompido com a imposição dos estresses, principalmente sob efeito do encharcamento do solo, o que se deve em grande parte à diminuição substancialmente da A, ao bloqueio no transporte de carboidratos para os tecidos drenos e ao aumento de MDA.
Soil waterlogging is a common problem in some agricultural areas, including regions under soybean (Glycine max) cultivation. In waterlogged soils, soil O2 depletion occurs due to aerobic microorganisms and plants, affecting the metabolic and physiological processes of plants after suffering anoxia in their root tissue. Another harmful factor of this situation is the exponential increase in the availability of iron (Fe) in the soil, which may result in excessive Fe uptake by plants. In the first experiment, the objective was to evaluate the vulnerability of the photosynthetic apparatus and biomass production of two soybean cultivars at the phenological stage V2, under optimal water condition and different levels of soil waterlogging, combined with one moderate and two toxic levels of Fe. While in the second experiment, the objective was to evaluate the physiological and biochemical behaviour of soybean cultivar Agroeste 3680, associated with the development of pods (at the phenological stage R3) in non-waterlogged and waterlogged soil, combined with one moderate and two toxic levels of Fe. In the first experiment, the photosynthetic apparatus of the two soybean cultivars responded differently to waterlogging and the availability of Fe in the soil. Both cultivars were vulnerable to waterlogging of 100% at all concentrations Fe, which resulted in damage to gas exchange and chlorophyll levels, and consequently, led to lower shoot and root biomass accumulation. The photosynthetic performance and dry biomass production of Agroeste 3680 were not affected when exposed to moderate levels of Fe associated with waterlogging of 50%. NS 6601 IPRO cultivar also showed a moderate tolerance to excess Fe when not waterlogged, since net photosynthetic rate, instantaneous carboxylation efficiency and chlorophyll a content were not affected. In the second experiment, gas exchange was strongly affected by soil waterlogging. Excess Fe without soil waterlogging reduced photosynthetic pigments, and potentiated this reduction when associated with soil waterlogging. Starch and ureides accumulated in the first newly expanded trifoliate leaves could be considered efficient biomarkers, indicating phytotoxicity caused by soil waterlogging and Fe excess in soybean plants. Thus, this finding can be used as a parameter to identify tolerable varieties to these abiotic conditions. The reproductive development was abruptly interrupted by the imposition of the stresses, leading to loss of pod dry biomass, particularly under soil waterlogging, which was largely due to the substantial decrease in A, the blockage of carbohydrate transport to sink tissues and an increase of MDA.
Soil waterlogging is a common problem in some agricultural areas, including regions under soybean (Glycine max) cultivation. In waterlogged soils, soil O2 depletion occurs due to aerobic microorganisms and plants, affecting the metabolic and physiological processes of plants after suffering anoxia in their root tissue. Another harmful factor of this situation is the exponential increase in the availability of iron (Fe) in the soil, which may result in excessive Fe uptake by plants. In the first experiment, the objective was to evaluate the vulnerability of the photosynthetic apparatus and biomass production of two soybean cultivars at the phenological stage V2, under optimal water condition and different levels of soil waterlogging, combined with one moderate and two toxic levels of Fe. While in the second experiment, the objective was to evaluate the physiological and biochemical behaviour of soybean cultivar Agroeste 3680, associated with the development of pods (at the phenological stage R3) in non-waterlogged and waterlogged soil, combined with one moderate and two toxic levels of Fe. In the first experiment, the photosynthetic apparatus of the two soybean cultivars responded differently to waterlogging and the availability of Fe in the soil. Both cultivars were vulnerable to waterlogging of 100% at all concentrations Fe, which resulted in damage to gas exchange and chlorophyll levels, and consequently, led to lower shoot and root biomass accumulation. The photosynthetic performance and dry biomass production of Agroeste 3680 were not affected when exposed to moderate levels of Fe associated with waterlogging of 50%. NS 6601 IPRO cultivar also showed a moderate tolerance to excess Fe when not waterlogged, since net photosynthetic rate, instantaneous carboxylation efficiency and chlorophyll a content were not affected. In the second experiment, gas exchange was strongly affected by soil waterlogging. Excess Fe without soil waterlogging reduced photosynthetic pigments, and potentiated this reduction when associated with soil waterlogging. Starch and ureides accumulated in the first newly expanded trifoliate leaves could be considered efficient biomarkers, indicating phytotoxicity caused by soil waterlogging and Fe excess in soybean plants. Thus, this finding can be used as a parameter to identify tolerable varieties to these abiotic conditions. The reproductive development was abruptly interrupted by the imposition of the stresses, leading to loss of pod dry biomass, particularly under soil waterlogging, which was largely due to the substantial decrease in A, the blockage of carbohydrate transport to sink tissues and an increase of MDA.
Descrição
Palavras-chave
Trocas gasosas, Clorofilas, Anoxia, Íon ferroso, Glycine max, Anoxia, Ferrous ion, Starch, Ureides