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Lipid peroxidation in soybean seed during imbibition - an example of oxidative stress in hypoxic conditions

The high lipid and protein content in soybean seed makes it prone to oxidative stress and is related to fast seed vigour decline with seed age. Being considered as the primary couse of seed vigour loss during storage, lipid peroxidation results with membrane damage in seed cells. Furthermore, after sowing in the field, seed can be exposed to hypoxia due to high rainfall, and rapid water uptake in dry seed can result with so-called imbibitional damage. The lack of oxygen in water-saturated soil causes a shift towards anaerobic seed metabolism, ROS production and lipid peroxidation-mediated cell membranes destruction. Here, we investigated the intensity of lipid peroxidation (TBARS – thiobarbituric acid reactive substances content) in seed testa, embrio and cotyledons of two soybean cultivars, after 3, 6, 12 and 24 h of seed soaking (imbibition) in deionized water, at 20oC. Simultaneously, seed electrical conductivity was measured in soaking water as the parameter of the electrolyte leaching from seed, which is mostly higher in low-vigour seed, in general. Regardless of seed age (6 and 18 months in storage after harvest) and cultivar, the lipid peroxidation was the highest in embrio, and lowest in seed testa. Considering the imbibition duration, the highest lipid peroxidation was observed after 3 h of soaking and it was significantly decreased thereafter, especially in the case of younger seed, what may imply better functioning of membrane reparation and/or antioxidative mechanisms activation. Seed electrical conductivity showed less pronounced seed leakage in cultivar Podravka, as compared to cultivar Vita (P≤0.01) that has also had higher lipid peroxidation in embrio (P≤0.05). The aged soybean seed has shown higher conductivity levels in general (53% higher in final measurement after 24 h of soaking), assuming more pronounced seed membrane damage.

hypoxia ; imbibition ; lipid peroxidation ; oxidative stress ; soybean

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