No abstract

Biochar application is an effective method for agriculture production. In order to study the biochar effect on soybean (Glycine max [L.] Merr.) seedling root growth, this study was conducted in a sand culture experiment using two soybean cultivars with different P efficiencies. Soybean was pot-grown at four biochar rates (0%, 0.15%, 0.75% and 1.5%, w/v). The results showed no difference in Cultivar × Biochar interaction on root morphologic characteristics. At 7 d after germination (DAG), biochar slightly enhanced root growth; at 10 DAG, biochar significantly increased total root length (TRL) and total root surface area (TRSA) highest by 48.4% and 27.4% (P < 0.05) at 1.5% biochar rate, respectively, compared to the control. The positive effects on root morphology by biochar were especially concentrated on fine roots (< 0.5 mm). In addition, root vitality and leaf soluble sugar content were significantly increased by both 0.75% and 1.5% biochar; shoot biomass increased maximally by 65.6% at 1.5% biochar rate compared to the control; inversely, root/shoot ratio significantly reduced by 32.3% and 23.5% at 1.5% biochar rate, respectively, at 7 and 10 DAG. We suggest that biochar had positive effects on soybean seedling growth through improving root morphology and root vitality, regardless of different P efficient cultivars.

Phosphorus (P) is one the least available essential plant macronutrients in soils that is a major constraint on plant growth. Soybean (Glycine max L.) production is often limited due to low P availability. The better management of P deficiency requires improvement of soybean’s P use efficiency. Sugars are implicated in P starvation responses, and a complete understanding of the role of sucrose together with P in coordinating P starvation responses is missing in soybean. This study explored global metabolomic changes in previously screened low-P-tolerant (Liaodou, L13) and low-P-sensitive (Tiefeng 3, T3) soybean genotypes by liquid chromatography coupled mass spectrometry. We also studied the root morphological response to sucrose application (1%) in P-starved soybean genotypes against normal P supply. Root morphology in L13 genotype has significantly improved P starvation responses as compared to the T3 genotype. Exogenous sucrose application greatly affected root length, root volume, and root surface area in L13 genotype while low-P-sensitive genotype, i.e., T3, only responded by increasing number of lateral roots. Root : shoot ratio increased after sucrose treatment regardless of P conditions, in both genotypes. T3 showed a relatively higher number of differentially accumulated metabolites between P-starved and normal P conditions as compared to L13 genotype. Common metabolites accumulated under the influence of sucrose were 5-O-methylembelin, D-glucuronic acid, and N-acetyl-L-phenylalanine. We have discussed the possible roles of the pathways associated with these metabolites. The differentially accumulated metabolites between both genotypes under the influence of sucrose are also discussed. These results are important to further explore the role of sucrose in the observed pathways. Especially, our results are relevant to formulate strategies for improving P efficiency of soybean genotypes with different P efficiencies.

Phosphorus (P) is an essential element for the growth and development of plants. Soybean (Glycine max) is an important food crop that is grown worldwide. Soybean yield is significantly affected by P deficiency in the soil. To investigate the molecular factors that determine the response and tolerance at low-P in soybean, we conducted a comparative proteomics study of a genotype with low-P tolerance (Liaodou 13, L13) and a genotype with low-P sensitivity (Tiefeng 3 , T3) in a paper culture experiment with three P treatments i.e., P-free (0 mmol·L -1), low-P (0.05 mmol·L -1), and normal-P (0.5 mmol·L -1). A total of 4,126 proteins were identified in roots of the two genotypes. Increased numbers of differentially expressed proteins (DEPs) were obtained from low-P to P-free conditions compared to the normal P treatment. All DEPs obtained in L13 (660) were up-regulated in response to P deficiency, while most DEPs detected in T3 (133) were down-regulated under P deficiency. Important metabolic pathways such as oxidative phosphorylation, glutathione metabolism and carbon metabolism were suppressed in T3, which could have affected the survival of the plants in P-limited soil. In contrast, L13 increased the metabolic activity in the 2-oxocarboxylic acid metabolism, carbon metabolism, glycolysis, biosynthesis of amino acids, pentose phosphatase, oxidative phosphorylation, other types of O-glycan biosynthesis and riboflavin metabolic pathways in order to maintain normal plant growth under P deficiency. Three key proteins (I1KW20 (prohibitins), I1K3U8 (alpha amylase inhibitors), and C6SZ93 (alpha amylase inhibitors) were suggested as potential biomarkers for screening soybean genotypes with low P tolerance. Overall, this study provides new insights into the response and tolerance to P deficiency in soybean.

No abstract