Root Foraging in Soybean (Glycine max) under Nitrogen Deprivation

Abstract

Nitrate is one of the key sources of nitrogen in natural and agricultural soils. The distribution and concentration of nitrate determine root system architecture in plants. Soybean (Glycine max L) is one of the key leguminous crops, while farmers rarely apply nitrogen in soybean crops except for a starter nitrogen dose at the time of sowing. However, the effects of severe deficiency nitrate on early seedling establishment of soybean before nodulation are not yet studied. Therefore, this study evaluated the effects of high dose of nitrate (54.3 mM) and its deprivationon (0 mM) on the root system architecture of soybean during seedling establishment. Results showed that the root traits including primary root length, fresh biomass, total length, surface area, tips, forks, and its crossings were significantly higher under no nitrate condition than nigh nitrate condition except for root volume, its dry biomass and diameter. Shoot growth attributes such as shoot length, shoot fresh biomass, shoot dry biomass, single leaf area, soil-plant analysis development value, and photosynthesis was significantly decreased while leaf dry mass per area was increased significantly under no nitrate condition. Furthermore, high nitrate supply significantly enhanced the content of nitrate in root tissue, but there was no significant difference between low and optimal nitrate supply. In summary, this study indicated that soybean root system architecture adopts a foraging strategy under nitrogen deprived environment. © 2021 Friends Science Publishers