Responses of Japanese Soybeans to Hypoxic Condition at Rhizosphere Were Different Depending upon Cultivars and Ambient Temperatures

Abstract

To investigate the soybean (Glycine max Merr.) wet endurance, and the affect of the maturity and the ambient temperature to the response, the plantlet in growth stage ranged from R1 to R2 of 8 Japanese soybean cultivars which characterized as various wet endurance in a past report were cultured under hypoxic-hydroponic condition for a month. Two experiments at different periods differed significantly in temperature of air and hydroponic solution, but the oxygenic condition were similar each experiments, as aimed for. And also, control and hypoxia treatments significantly differed in dissolved oxygenic concentration in each experiments. The hypoxic condition at higher temperature induced the reduction of survival of plantlet up to 70%. At higher temperature, the survival rate of late maturity types "Yuzuru" and "Shirotsurunoko" were decreased significantly in hypoxic condition than in control. Similarly, the shoot dry matters of them were also decreased significantly in hypoxia at higher temperature. The tendency of the decreasing in hypoxia was remarkable in the pod dry matter, and the symptoms were shown also at the lower temperature. From these results, soybean's hypoxic tolerant may be reflected with the wet endurance, the process of hypoxic damages can be divided to sudden death symptom and biomass decreasing, and the mechanisms of hypoxic tolerance might be affected strongly by ambient temperature, and absolutely controlled with the genetic background.

Hypoxia-Responsive Root Hydraulic Conductivity Influences Soybean Cultivar-Specific Waterlogging Tolerance

“…Although the use of a comparative physiological approach might provide new insights into soybean waterlogging tolerance, there are no available reports describing studies involving several cultivars under normal and oxygen-stress conditions in the root zone. The responses of eight Japanese soybean cultivars to hypoxic conditions were compared in a short-term hydroponic culture system [17] [18]. The results revealed a cultivar-specific waterlogging tolerance during the immature growth stage without the development of adventitious roots or aerenchyma.…”

“…Some of the cultivars have exhibited unique waterlogging tolerance [15]. "Enrei" ("Ere"), which is widely grown in Japan, is insensitive to hypoxia, and has been used as a standard soybean cultivar [17]. "Toyomusume" ("TMu") seed responses to flooding and plant responses to hypoxia have been investigated [8] [18].…”

“…Soybean seeds were germinated on wet paper towels in an EYELA MTI-202 incubator (Tokyo Rikakikai Co, Ltd., Tokyo, Japan) at 25˚C in darkness [17] [18]. …”

“…Some researchers have indicated that high carbon dioxide levels [30] [31] [32] or impaired mineral diffusion [33] in the rhizosphere are key factors influencing crop waterlogging injury. Additionally, low partial pressure of oxygen around the roots [17] [34] should be considered an important factor in the development of waterlogging injury in soybean plants.…”

Morphological root responses of soybean to rhizosphere hypoxia reflect waterlogging tolerance

“…Although a physiological approach is necessary for determining soybean waterlogging tolerance, comparisons of the morphological response among soybean genotypes in rhizospheres that differ in oxygen status have not been reported. In a previous study, the hypoxic responses of eight Japanese soybean cultivars were compared under different rhizosphere oxygen conditions, and a close relationship was shown between cultivar-specific hypoxic response and field waterlogging tolerance (Jitsuyama 2013).…”