Does Pre-Germination Flooding-Tolerant Soybean Cultivar Germinate Better under Hypoxia Conditions?

Abstract

The germination and emergence of soybean [Glycine max (L.) Merr.] can be adversely affected by the presence of excessive water as a result of continuous rainfall. The pre-germination flooding-tolerant cultivars can be tolerant to hypoxia in the flooding field. The objective of this study was to clarify the relationship between germination under hypoxia at different temperatures and pre-germination flooding tolerance. Seeds of 6 soybean cultivars were subjected to 5 oxygen concentrations and 3 temperatures. Seeds of all 6 cultivars hardly germinated under an oxygen concentration of 20 mL L–1, but germinated with increasing oxygen concentration regardless of temperature. The pre-germination flooding-tolerant cultivar ‘Peking’ exhibited poorer germination under hypoxia than the other cultivars. Seed coat of ‘Peking’ did not dehisce when seeds did not germinate under hypoxia regardless of temperature. The pre-germination flooding-susceptible cultivar ‘Nakasennari’ exhibited higher seed coat dehiscence, but the dehiscence mostly occurred on the seed surface rather than micropyle under hypoxia at 25°C and 30°C. Seven days after termination of 3-d hypoxia treatment at 30°C, the percentage of seedlings with root hairs and/or lateral roots relative to that after ambient oxygen treatment was maintained in ‘Peking’ but decreased in the other cultivars, especially in ‘Nakasennari’. Pre-germination flooding-tolerant cultivar, especially ‘Peking’, is characterized by a delay in germination processes under hypoxia, and exhibits vigorous germination after release from hypoxia.