ObjectivesEffects of γ-polyglutamic acid (γ-PGA) on growth, yield and quality of Chinese flowering cabbage were studied to provide a support for its use in agricultural production.
MethodsA pot experiment was conducted using Chinsese flowering cabage as tested crop in an acid soil (pH 5.89) and a strong acid soil (4.85). At the base of applying N 1.33 g/kg soil in 5 times, five treatments were designed:no γ-PGA applicaiton (T1), applying γ-PGA 0.53 mg/kg soil (T2) and 1.06 mg/kg soil (T3) in five times with N fertilization, and applying γ-PGA 0.53 mg/kg soil (T4) and 1.06 mg/kg soil (T5) once after seedling transplanting. The root activity, nutrient contents, nutrient accumulation, antioxidant system, yield and quality of Chinese flowering cabbage of each treatment were determined.
ResultsIn both the acid and strong acid soils, the bleeding intensities of Chinese flowering cabbage in T2, T3, T4 and T5 were slightly higher than that in T1, and the amino acid intensities in the bleeding sap in T3, T4 and T5 were significantly higher than in T1 (P < 0.05) with the average increased rates of 38.1%, 33.2% and 44.2%, respectively. In the acid soils, the Ca and Mg contents of Chinese flowering cabbage in T2, T3, T4 and T5 were significantly higher than that in T1 (P < 0.05), with the increased rates of 29.6%, 21.8%, 26.4%, 22.7% in acid soil and 1.7%, 8.3%, 22.2%, 16.7% in strong acid soil condition, respectively. The Zn and Mn contents in Chinese flowering cabbage were increased slightly in the treatments of T2, T3, T4 and T5 in the acid soils, no differences in strong acid soils. The accumulated amounts of N, P, K, Ca, Mg, Cu, Zn, Fe and Mn in Chinese flowering cabbage in the acid soils and the strong acid soils were increased greatly by applying γ-PGA. In the strong acid soils, the soluble protein contents in leaves of Chinese flowering cabbage in T4 and T5 were significantly higher than that in T1, and the CAT activities in T2, T3, T4 and T5 were significantly higher than in T1 (P < 0.05). While in the acid soils, the CAT activity of leaves of Chinese flowering cabbage was increased significantly only in T3. In both the acid and strong acid soils, SOD activities of leaves of Chinese flowering cabbage were increased significantly in T3 and T4 than in T1 (P < 0.05), while not in the POD activities. The yields of T2, T3, T4 and T5 were significantly higher than in T1 (P < 0.05), with the increases rate of 4.46%, 7.3%, 12.2% and 12.3% in acid soils and 9.7%, 14.2%, 12.2% and 12.3% in strong acid soils. The aboveground and root biomass of T2, T3, T4 and T5 were significantly higher than those of T1 (P < 0.05). The VC and free amino acid contents in T4 and T5 were significantly higher than those of T1 (P < 0.05), and the nitrate contents were decreased greatly in the γ-PGA applied treatments (T2, T3, T4 and T5) as compared with T1. The root activities, nutrient contents, nutrient accumulation amounts, antioxidant system, yields and quality of Chinese flowering cabbage in the γ-PGA treatments were higher than those in the γ-PGA coated fertilizer treatments. No significant differences in the yields, quality, mineral nutrition, and antioxidant system were observed among different γ-PGA dosages. The γ-PGA primary increased the uptakes of nutrients in Chinese flowering cabbage in the acid soils, while the γ-PGA mostly strengthened the antioxidant system of Chinese flowering cabbage in the strong acid soils.
ConclusionsThe γ-PGA application enhanced the root activities of Chinese flowering cabbage, increased the uptake and accumulation of mineral nutrients (bivalent cation especially) in Chinese flowering cabbage, strengthened the stress resistance of Chinese flowering cabbage, and increased the yield of Chinese flowering cabbage. Once application of γ-PGA in the tested dosage performs better than that apllied in five times.
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