根际不同供氮水平对紫青菜生长和营养品质的影响

Effect of Nitrogen Supply Level in Rhizosphere on Growth and Nutritional Quality of Purple Pak-choi

摘要:

为了解根际供氮对紫青菜(Brassica campestris ssp. chinensis var. communis)生长和营养品质的影响,用不同水平的NH₄NO₃处理,对紫青菜的生理特性和营养品质进行研究。结果表明,随着供氮水平的增加,紫青菜的鲜质量、干质量、根系活力和游离氨基酸含量均呈先上升后略下降趋势;硝酸还原酶(NR)活性、叶绿素含量、NO₃^-含量和可溶性蛋白质含量均呈上升趋势;DPPH·自由基清除率、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)同工酶和过氧化氢酶(CAT)同工酶活性等均提高;而花青素苷相对含量、可溶性糖含量、维生素C (Vc)含量、总酚含量和FRAP值均呈下降趋势。根际NH₄NO₃为75~300 mg L^-1时,紫青菜的鲜质量和干质量较低;NH₄NO₃达1200 mg L^-1时,其鲜质量和干质量又低于600 mg L^-1处理的,植株积累较多NO₃^-,导致营养品质下降,同时根际也积累NH₄NO₃。因此,600 mg L^-1的根际NH₄NO₃是适宜的氮水平,其鲜质量和干质量均最高、营养均衡、抗氧化能力强。

关键词:氮素;紫青菜;生长;营养品质;抗氧化能力

Abstract:

In order to understand the effects of rhizosphere N supply on the growth and nutritional quality of purple pak-choi (Brassica campestris ssp. chinensis var. communis), the physiological and nutrition characters were studied treated with different levels of NH₄NO₃. The results showed that the fresh and dry weight, root activity, free amino acid content of purple pak-choi increased initially and then slightly decreased with the N level increment. Nitrate reductase (NR) activity, contents of chlorophyll, NO₃^- and soluble protein, and DPPH· radical scavenging rate increased, activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) isozymes showed upward trend, while the contents of relative anthocyanin, soluble sugar, vitamin C (Vc) and total phenols, and FRAP value decreased. Meantime, the fresh and dry weight of purple pak-choi treated with 75-300 mg L^-1 NH₄NO₃ was low. The fresh and dry weight treated by 1200 mg L^-1 NH₄NO₃ was lower than that by 600 mg L^-1 NH₄NO₃, more NO₃^- accumulated in plant led to decline of nutrient quality, and NH₄NO₃ deposited in rhizosphere. So, the optimum level of NH₄NO₃ was 600 mg L^-1 because of high fresh and dry weight, balanced nutrition and strong antioxidant ability.

Key words:Nitrogen;Purple pak-choi;Growth;Nutritional quality;Antioxidant ability