保水剂-尿素凝胶对侧柏裸根苗细根生长和氮素利用率的影响

在盆栽试验条件下,研究不施肥和保水剂(CK)、单施尿素(U)、单施保水剂(S)、保水剂-尿素混施(SUM)和保水剂-尿素凝胶(SUG)处理对侧柏裸根苗细根的形态特征、吸收面积、氮代谢及氮素利用率的影响.结果表明:与U处理相比,SUG处理显著增加细根的生物量、长度、比根长、表面积和体积,并明显扩大细根的总吸收面积和根尖吸收面积;SUG处理比根长分别较CK、U、S和SUM处理显著增加34.7%、37.9%、41.1%和12.4%,细根的硝酸还原酶、谷氨酰胺合成酶、谷氨酸合成酶和谷氨酸脱氢酶活性分别较U处理提高41.2%、76.6%、30.7%和125.8%,而GS/GDH(谷氨酰胺合成酶/谷氨酸脱氢酶)下降.SUG处理显著促进侧柏裸根苗地径、株高的生长以及地上部和地下部干物质积累,且氮素利用率达到40.7%,分别比U和SUM处理显著提高118.8%和44.5%.保水剂-尿素凝胶通过改善侧柏裸根苗细根的形态特征、提高吸收面积及氮代谢关键酶活性而提高氮素利用率,促进生长,并增强抵御干旱胁迫的能力.

Effects of gel made by super absorbent polymers and urea on fine root growth and nitrogen use efficiency of Platycladus orientalis bareroot seedlings.

A pot experiment including five treatments, i.e., CK (neither fertilizer nor super absorbent polymers), U (urea alone), S super absorbent polymers (SAP) alone], SUM (SAP mixed with urea) and SUG (gel made of SAP and urea) was conducted to evaluate their effects on fine root morphological characteristics, fine root absorption area, fine root nitrogen metabolism and nitrogen use efficiency of Platycladus orientalis bareroot seedlings. Results showed that compared with U treatment, the SUG treatment significantly increased the biomass, length, specific root length, surface area and volume of fine root. The total absorption area and active absorption area of fine root were also increased remarkably under the SUG treatment. The specific root length in the SUG treatment was increased by 34.7%, 37.9%, 41.1% and 12.4% compared with the treatments of CK, U, S and SUM, respectively. Compared with the U treatment, the activities of nitrate reductase, glutamine synthase, glutamate synthase and glutamate dehydrogenase in fine root of the SUG treatment was improved by 41.2%, 76.6%, 30.7% and 125.8%, respectively, while the ratio of GS to GDH decreased. Not only the ground diameter and plant height, but also the dry matter accumulation of aboveground and underground parts was remarkably enhanced under the SUG treatment. The nitrogen use efficiency was 40.7% in the SUG treatment, being 118.8% and 44.5% higher than the U and SUM treatments, respectively. Gel made of SAP and urea was able to significantly increase the nitrogen use efficiency, promote the growth and enhance the ability of drought resistance by improving the morphological characteristics, enhancing the absorption area and key enzymes activities of nitrogen metabolism in the fine root of P. orientalis bareroot seedlings.