Soybean Root Growth in Response to Chemical, Physical, and Biological Soil Variations

Short-Term Effects of Cenchrus fungigraminus/Potato or Broad Bean Interplanting on Rhizosphere Soil Fertility, Microbial Diversity, and Greenhouse Gas Sequestration in Southeast China

Cenchrus fungigraminus is a new species and is largely used as forage and mushroom substrate. However, it can usually not be planted on farmland on account of local agricultural land policy. Interplanting Cenchrus fungigraminus with other crops annually (short-term) is an innovative strategy to promote the sustainable development of the grass industry in southern China. To further investigate this, C. fungigraminus mono-planting (MC), C. fungigraminus-potato interplanting (CIP) and C. fungigraminus-broad bean interplanting (CIB) were performed. Compared to MC, soil microbial biomass carbon (SMBC), soil organic matter (SOM), ammoniacal nitrogen (AMN), pH and soil amino sugars had a positive effect on the rhizosphere soil of CIP and CIB, as well as enhancing soil nitrogenase, nitrite reductase, and peroxidase activities (p < 0.05). Moreover, CIP improved the root vitality (2.08 times) and crude protein (1.11 times). In addition, CIB enhanced the crude fiber of C. fungigraminus seedlings. These two interplanting models also improved the microbial composition and diversity (Actinobacteria, Firmicutes, and Bacteroidota, etc.) in the rhizosphere soil of C. fungigraminus seedlings. Among all the samples, 189 and 59 genes were involved in methane cycling and nitrogen cycling, respectively, which improved the presence of the serine cycle, ribulose monophosphate, assimilatory nitrate reduction, methane absorption, and glutamate synthesis and inhibited denitrification. Through correlation analysis and the Mantel test, the putative functional genes, encoding functions in both nitrogen and methane cycling, were shown to have a significant positive effect on pH, moisture, AMN, SOM, SMBC, and soil peroxidase activity, while not displaying a significant effect on soil nitrogenase activity and total amino sugar (p < 0.05). The short-term influence of the interplanting model was shown to improve land use efficiency and economic profitability per unit land area, and the models could provide sustainable agricultural production for rural revitalization.

Ascophyllum nodosum SWE enhances root anatomy, but not POD activity in both a salt-tolerant and salt-sensitive soybean ( Glycine max) variety exposed to salt stress

There is growing evidence that seaweed extracts (SWE) may be a solution for mitigating the negative effects of salt stress on crop yield and quality, as they introduce bioactive ingredients able to regulate the expression of growth-inducing and stress-responsive genes. We demonstrate that SWE slightly ameliorated the negative physical growth effects of salt stress, especially in the root anatomy of the salt-sensitive (Clark) variety. The SWE did not stimulate or enhance peroxidase (POD) activity in either the salt-sensitive (Clark) or salt-tolerant variety (Manokin). However, a complete assessment of other antioxidant enzymes (SOD, CAT, APX) involved in the ROS detoxification process is further required.

Effects of Different Land Use Patterns on Soil Water in Loess Hilly and Gully Regions of China

Soil water is a major barrier to ecological restoration and sustainable land use in China’s Loess Hilly Region. For the restoration of local vegetation and the optimal use of the region’s land resources, both theoretically and practically, it is essential to comprehend the soil water regimes under various land use types. The soil water content in the 0−160 cm soil profile of slope cropland, terraced field, jujube orchard, and grassland was continuously measured using EC-5 soil moisture sensors during the growing season (May−October) in the Yuanzegou catchment in the Loess Hilly Region to characterize the changes in soil water in these four typical land use types. The results showed that in both years of normal precipitation and drought, land use patterns varied in seasonal variability, water storage characteristics, and vertical distribution of soil water. In the dry year of 2015, the terraced field effectively held water. During the growing season, the 0−60 cm soil layer’s average soil water content was 2.6%, 4.2%, and 1.8% higher than the slope cropland, jujube orchard, and grassland, respectively (p < 0.05), and the 0−160 cm soil layer’s water storage was 43.90, 32.08, and 18.69 mm higher than the slope cropland, jujube orchard, and grassland, respectively. The average soil water content of the 0−60 cm soil layer in the jujube orchard was 2.9%, 3.8%, and 4.5% lower than that of slope cropland, terraced field, and grassland, respectively, during the normal precipitation year (2014) (p < 0.05). Only 35.0% of the total soil water storage was effectively stored in the 0−160 cm soil layer of the jujube orchard during the drought year. There was a significant difference in the grey relational grade between the soil water in the top layer (0−20 cm) and the soil water in the middle layer (20−100 cm) under different land use types, with the terraced field having the highest similarity degree of soil water variation trend, followed by grassland, slope cropland, and jujube orchard. Slope croplands in the study region may be converted into terraced fields to enhance the effective use of rainfall resources and encourage the expansion of ecological agriculture. Proper water management practices must be employed to reduce jujube tree water consumption and other wasteful water usage in order to guarantee the jujube orchard’s ability to expand sustainably. This would address the issue of the acute water deficit in the rain-fed jujube orchards in the Loess Hilly Region.

Evolving role of synthetic cytokinin 6-benzyl adenine for drought stress tolerance in soybean (Glycine max L. Merr.)

The enhanced growth and productivity of soybeans during the past decades were possible due to the application of agrichemicals such as bio-fertilizers, chemical fertilizers, and the use of high yielding, as well as disease resistant transgenic and non-transgenic varieties. Agrichemicals applied as seed primers, plant protectants, and growth regulators, however, had a diminutive significance on growth and productivity improvements across the globe. The utilization of plant growth regulators (PGRs) for vegetative growth, reproduction and yield quality improvements remains unexplored, particularly, the use of cytokinins such as 6-benzyl adenine (6-BAP) to improve soybean response to abiotic stresses. Therefore, an understanding of the role of 6-BAP in the mediation of an array of adaptive responses that provide plants with the ability to withstand abiotic stresses must be thoroughly investigated. Such mitigative effects will play a critical role in encouraging exogenous application of plant hormones like 6-BAP as a mechanism for overcoming drought stress related effects in soybean. This paper discusses the evolving role of synthetic cytokinin 6-bezyl adenine in horticulture, especially the implications of its exogenous applications in soybean to confer tolerance to drought stress.

Physiology and metabonomics reveal differences in drought resistance among soybean varieties

BACKGROUND

The soybean is an important food crop worldwide. Drought during the first pod stage significantly affects soybean yield, and understanding the metabolomic and physiological changes in soybeans under drought stress is crucial. This study identified the differential metabolites in initial pod stage soybean leaves under polyethylene glycol-simulated drought stress, using ultra performance liquid chromatography and tandem mass spectrometry, and the physiological indexes related to drought resistance.

RESULTS

Physiologically, drought resistance also generates enzyme and antioxidant activity; levels of superoxide dismutase, peroxidase, and catalase first increased and subsequently decreased, while those of soluble sugar, soluble protein, malondialdehyde, and proline content increased in both varieties. The contents of CAT, proline and soluble sugar in Heinong 44 (HN44) were higher than those in Heinong 65 (HN65), and the contents of MDA were lower than those in HN65. In metabolomics, the OPLS-DA model was used to screen different metabolites. KEGG analysis showed that the two varieties resisted drought through different ways. Amino acid metabolism and lipid metabolism play a key role in drought resistance of the two varieties, respectively. TCA cycle was one of the core pathways of drought resistance in two varieties. Changes in the content of L-Asparagine and citric acid may be one of the reasons for the difference in drought resistance between the two varieties.

CONCLUSIONS

We think that the reasons of drought resistance among soybean varieties are as follows: the main metabolic pathways are different under drought stress; the contents of metabolites in these metabolic pathways are different; some physiological indexes are different, such as MDA, CAT, proline content and so on. Our study enhances the understanding of the metabolomic soybean drought stress response and provides a reference for soybean drought resistance breeding.