Effect of Drought Stress at Reproductive Stages on Growth and Nitrogen Metabolism in Soybean

Abstract

This study aims to determine variability among soybean (Glycine max (L.) Merr.) cultivars under drought conditions and how nitrogen metabolites, metabolism-related enzymes, and gene expression vary during soybean growth. Three soybean cultivars, Shennong17 (CV.SN17), Shennong8 (CV.SN8), and Shennong12 (CV.SN12), were grown in pot culture and subjected to drought stress at reproductive stages for 45 days. The results showed that long-term drought stress decreased biomass allocation to reproductive organs, weakened antioxidant capacity, and reduced seed weight, effects that were less pronounced in CV.SN12 compared with those in CV.SN8 and CV.SN17. Drought stress decreased the concentrations of nitrogen and soluble protein but increased nitrate concentration in leaves. This was related to the significantly reduction of nitrogen metabolism efficiency, including decreased activities of nitrogen metabolism enzymes, and downregulated expression of GmNR, GmNiR, GmGS, and GmGOGAT. Drought stress increased the concentrations of free amino acid, proline, and soluble sugar in leaves to enhance the osmotic adjustment ability. Furthermore, soybean seed weight showed significantly correlation (p < 0.05) with nitrogen-metabolism-related parameters. Based on the performance of growth, nitrogen metabolism, and yield attributes, CV.SN12 showed the highest tolerance to drought, followed by CV.SN8 and CV.SN17. In addition, these nitrogen-metabolism-related parameters could be used in soybeans to select for drought tolerance.

Response of Soybean (Glycine max (L.) Merrill) to Mineral Nitrogen Fertilization and Bradyrhizobium japonicum Seed Inoculation

“…Aldana; hence a reduced plant density and a relatively low air temperature in 2018 and 2019 in July and August, and an accompanying low total rainfall affecting growth, development and yield of soybean. Similar observations were made before not only in Poland [11] but also in the United States [40], Serbia [41] or in China [14]. The average air temperature at the flowering and pod formation stage, although higher than the long-term mean in Poland, was much lower than 25 • C, which Montanez et al [8] consider most favorable for the soybean yield and biological N fixation.…”

“…The applicable literature reports on a possible long-term water stress deteriorating the morphological traits of soybean plants [13,14]. Mrkovacki and Morinkovic [47] claim that mineral N enhances the height of soybean plants.…”

“…Therefore, a decreased N content in plants subjected to drought stress indicates a significant decrease in the activity of N fixation [13]. According to Du et al [14], a long-term water stress, especially if it occurs at the flowering and seed filling stage (BBCH 60-75), decreases the allocation of nutrients to generative parts, thereby reducing the seed weight per pod, as well as the N and protein content in soybean seeds [15]. The ability of soybean plants to feed on mineral N and nitrogen derived from symbiosis with B. japonicum is closely related.…”

Effect of planting density and row spacing on the yielding of soybean (Glycine max L. Merrill)

“…merely 22.4% and 21.2% of the yields recorded in 2016, which was the most favourable year in terms of humidity. It was probably the result of disturbing the intracellular water relations and the inhibition of plant growth (Wojtyla et al 2020), a decreasing supply of nutrients to generative organs (Du et al 2020) and a significant decrease in the activity of N fixation (Streeter 2003) under such conditions, which decreased the yield of seeds and protein in soybean. An almost 100% correlation between a decrease in the yield of seeds and protein in soybean in the subsequent years indicates a significant effect of humidity on the value of both traits, however most probably without an essential change in the seed protein content.…”

Seasonal Functional Partitioning of Carbohydrates and Proline among Plant Parts of the Sand Daffodil

“…However, the maintenance of petal expansion-during a 3-month dry period-seems to be ameliorated by adjustment via osmotic agents, such as proline and soluble sugars, translocated through plant tissues [52][53][54]. It has been argued that reproductive organs are constructed from resources either recently acquired, or previously stored by the vegetative parts [48,55]. In fact, elevated accumulation of soluble sugars and proline in petals (from June to August) may result to a reduction of their osmotic potential, which is expected to sustain their turgor and avoid the harmful effect of desiccation, during the dry period.…”