Physio-biochemical behaviour of soybean in response to soil waterlogging associated with excess iron

Author(s)

Allan de Marcos Lapaz

• Document type: Master's Dissertation
• Press: Ilha Solteira. 2020-01-27.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Engenharia. Ilha Solteira
• Defense date: 2019-12-17
• Advisor: Ana Carolina Firmino; Liliane Santos de Camargos; Rafael Simões Tomaz

Abstract

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. (AU)

• FAPESP's process: 18/17380-4 - Evaluation of soybean varieties physiological and agronomic traits under different iron concentrations and under ideal hydric conditions and waterlogging
• Grantee: Allan de Marcos Lapaz
• Support Opportunities: Scholarships in Brazil - Master