氮素形态对穿心莲氮吸收、分配和内酯成分积累的影响

Effects of nitrogen forms on nitrogen uptake and allocation and andrographolide components accumulation in Andrographis paniculata

关键词:  氮素形态, 氮吸收, 氮分配, 穿心莲内酯, 穿心莲

Key words:  nitrogen form, nitrogen uptake, nitrogen allocation, andrographolide, Andrographis paniculata

摘要:

为了明确药用植物穿心莲(Andrographis paniculata)对不同氮素形态的利用特征及其与穿心莲内酯成分积累的关系,以硝态氮(NN)、铵态氮(AN)、酰胺态氮(UN)和氨基酸态氮(GN)为单一氮源,采用¹⁵N同位素示踪和生理生化分析,研究了氮素形态对穿心莲不同生长时期(快速生长期、拔节期、现蕾期、开花期)氮素吸收、分配和穿心莲内酯成分含量的影响。结果表明:(1)叶片和根中氮含量随生长时期逐渐下降,NN处理氮含量较低。(2)穿心莲氮吸收速率在营养生长期较高,生殖生长期急速下降,穿心莲对AN、UN和GN的吸收速率较高。(3)现蕾期叶片氮分配比例减少,茎氮分配比例增加,与NN处理相比,该时期AN、UN和GN处理降低了叶片氮分配比例,而提高了茎和根氮分配比例。(4)快速生长期NN处理的光合作用最大羧化速率和最大电子传递速率较低,叶片氮在羧化系统和生物能学组分中的分配比例也较低; UN和AN处理分别在现蕾期和开花期降低了叶片氮在羧化系统中的分配。(5)AN、UN和GN提高了穿心莲内酯和脱水穿心莲内酯含量,降低了现蕾期和开花期14-去氧穿心莲内酯含量,不同氮素形态对新穿心莲内酯的影响较小。(6)穿心莲内酯和新穿心莲内酯含量与叶、茎、根氮含量,氮吸收速率及叶和根中氮分配比例显著负相关,而与茎中氮分配比例显著正相关,14-去氧穿心莲内酯则相反。综上认为,营养生长期是穿心莲氮吸收的主要时期,穿心莲能更好地利用铵态氮、酰胺态氮和氨基酸态氮,并通过优化氮分配促进穿心莲内酯成分积累。

Abstract:

Nitrogen(N)is a mineral nutrient with the highest demand for plants, and it is also a vital abiotic factor that limits plant yield and quality. Plants use inorganic and organic N sources from soil, and N form is a key factor affecting the active ingredients and their contents in medicinal plants. However, the utilization characteristics of different N forms by medicinal plants and the impact on active ingredients remain to be investigated. With nitrate nitrogen(NN), ammonium nitrogen(AN), amide nitrogen(urea, UN)and amino acid nitrogen(glycine, GN)as sole N source and combining ¹⁵N isotope tracing and physiological and biochemical analysis, this study aimed to clarify the characteristics of N uptake and utilization and its effect on the accumulation of andrographolide components at different growth stages(rapid growth stage, jointing stage, budding stage, flowering stage)of Andrographis paniculata. The results were as follows:(1)N contents in leaf and root decreased gradually with the growth stage, and it was lower in the NN treatment.(2)The uptake rate of N was higher in the vegetative growth stage, and rapidly decreased in the reproductive growth stage. The uptake rates of AN, UN and GN were higher than that of NN in A. paniculata.(3)The allocation ratio of N in leaf was decreased, while the allocation ratio of N in stem was increased at budding stage. In comparison to the NN treatment, AN, UN, and GN treatments reduced N allocation ratio in leaf, but increased the ratios in stem and root at this growth stage.(4)At rapid growth stage, the maximum carboxylation rate and maximum electron transport rate of photosynthesis were lower in the NN treatment, as well as the proportion of leaf N allocation in the carboxylation system and bioenergetics components. The allocation of leaf N in the carboxylation system in UN and AN treatments were reduced at budding and flowering stages, respectively.(5)AN, UN and GN increased andrographolide and dehydroandrographolide contents, and decreased 14-deoxyandrographolide content at budding and flowering stages, while neoandrographolide was slightly affected by N forms.(6)The contents of andrographolide and neoandrographolide were significantly negatively correlated with N contents in leaf, stem and root, N uptake rate, and N allocation ratios in leaf and root, while they were significantly positively correlated with N allocation ratio in stem. The opposite was true for 14-deoxyandrographolide. Taken together, the results indicate that the vegetative growth stage is the main stage for N uptake in A. paniculata, and that A. paniculata can better utilize AN, UN, and GN, and promote the accumulation of andrographolide components by optimizing N allocation. The results provide a theoretical reference for N management of A. paniculata.