【作者】 丁文雅；

【导师】 林咸永；

【作者基本信息】 浙江大学 ， 植物营养学， 2012， 硕士

【摘要】 气雾栽培(雾培)技术是把植物根系置于空气或者气雾环境中,通过雾化的水气满足植物根系对水肥需求的一种栽培方式。它不仅摆脱了传统土壤栽培对天然土壤的依赖和免受土壤污染、连作障碍、次生盐渍化等对作物生产的限制,而且有效解决普通水培中根系供氧问题,同时具有养分和水分利用率高的特点,不仅可用于蔬菜工厂化生产,而且适用于航天生命保障系统和庭院休闲农业,是一种具有广阔应用前景的新型无土栽培模式。营养液的配置和优化是雾培作物获得高产优质的关键技术。现有的蔬菜雾培大多沿用传统无土栽培的营养液配方,普遍以高浓度的硝态氮作为氮源而导致营养液中氮素浓度过高和形态不当,不仅造成生产成本提高,管理困难,而且引起蔬菜体内硝酸盐的大量积累,严重影响雾培蔬菜的营养品质。因此,阐明雾培营养液中氮素营养对蔬菜作物产量和品质的影响及其机理是协调解决雾培体系中成本-产量-品质的关键技术。但是,关于叶菜雾培的营养液配方及其优化缺乏系统的研究。本论文以生菜(Lactuca sativaL.)为材料,在选择适宜的叶菜雾培营养液配方和比较雾培与水培系统差异的基础上,进一步研究气雾栽培营养液中氮素水平、形态以及收获前氮素供应方式等对生菜产量、抗氧化物质含量及抗氧化活性的影响,旨在为高产优质蔬菜的雾培生产体系中营养液的供应和控制提供理论依据和技术支撑。取得的主要结果如下：(1)比较了Hoagland、日本园试、日本山崎、华南农大叶菜B、英国Hewitt等5个生菜常用的水培营养液配方对生菜产量和营养品质的影响。结果表明：华南农大叶菜B的营养液pH值升幅最小,英国Hewitt最大；华南农大叶菜B处理的生菜根系和地上部鲜质量、干质量最高,英国Hewitt或Hoagland处理的最低；华南农大叶菜B处理的生菜叶片还原型抗坏血酸含量、FRAP (ferric reducing/antioxidant power)抗氧化活性和DPPH (1,1-diphenyl-2-picrydrazyl)自由基清除率最高,日本园试次之,日本山崎最低；日本园试处理的生菜类胡萝卜素和谷胱甘肽含量最高,华南农大叶菜B次之,日本山崎最低；华南农大叶菜B处理的生菜可溶性糖含量最高,而可溶性蛋白质含量与日本园试相当,显著高于其他配方；华南农大叶菜B处理的生菜叶片和茎的硝酸盐含量显著低于英国Hewitt和Hoagland,略高于日本园试和日本山崎。说明采用华南农大叶菜B作为生菜气雾栽培的营养液配方,不仅营养液pH波动小,而且生菜具有较高的生物量、抗氧化物质含量和抗氧化活性以及较低的硝酸盐含量,是较为适宜的生菜气雾栽培配方,而英国Hewitt和日本山崎不适合生菜的气雾栽培。(2)研究了不同供氮水平(2、8、20mmol/L)下,雾培与水培生菜产量、营养品质及抗氧化活性的差异。结果表明,随着供氮水平的提高,两种栽培方式中生菜叶片和茎中硝酸盐与可溶性蛋白含量均显著增加,而可溶性糖、还原型抗坏血酸和谷胱甘肽含量、FRAP值和DPPH自由基清除率均逐渐降低,但根系形态指标、光合作用参数、地上部和根系鲜重、可溶性蛋白、可溶性糖、还原型抗坏血酸及谷胱甘肽积累量均以8 mmol/L处理最高。同一供氮水平下,雾培生菜根系生长(根系总长、根直径、根表面积、根体积和根系活力)、地上部和根系生物量、生长速率、叶片SPAD值、光合参数(净光合速率、气孔导度、胞间CO2浓度、蒸腾速率)均显著高于水培,而硝酸盐含量显著低于水培；雾培生菜叶片和茎的FRAP值和DPPH自由基清除率与水培相当或高于水培。虽然可溶性蛋白、可溶性糖、还原型抗坏血酸含量在雾培与水培生菜中没有显著差异,谷胱甘肽在水培生菜体内含量较高,但雾培生菜体内可溶性蛋白、可溶性糖、还原型抗坏血酸、谷胱甘肽等物质的积累量均显著高于水培。说明雾培较水培有利于生菜生物量和抗氧化物质的积累及抗氧化活性的提高,且在适宜的供氮水平(8 mmol/L)下上述优势尤其明显。(3)研究了不同供氮水平(4、8、12、16、20mmol/L)对雾培生菜的产量、抗氧化物质含量和抗氧化活性的影响。结果表明,氮水平从4 mmol/L提高到8mmol/L,雾培生菜生物量显著增加,体内氮素营养状况明显改善,但提高到12mmol/L没有明显变化,在高氮水平下(16、20mmol/L)反而降低了生物量,并导致硝酸盐的大量积累。随着供氮水平的提高,叶片和茎中可溶性糖含量逐渐降低,可溶性蛋白含量呈先增加后减少的趋势。叶片抗坏血酸、谷胱甘肽、总酚和类黄酮含量、FRAP值和DPPH自由基清除率均随着供氮水平的提高而逐渐下降,但是当供氮水平从4 mmol/L提高到8mmol/L时,除了抗坏血酸和DPPH自由基清除率显著下降外,谷胱甘肽、总酚、类黄酮含量以及FRAP值没有变化。因此,营养液中氮浓度为8mmol/L时,可基本满足雾培生菜对氮素营养的需要,保持较高生物量的同时具有较高的抗氧化物质含量和抗氧化活性以及较低的硝酸盐含量,是生菜雾培营养液中兼顾产量与品质的适宜供氮水平。(4)研究了营养液中不同硝铵比(100：0、75：25、50：50、25：75、0：100)对雾培生菜产量、营养品质和抗氧化活性的影响。结果表明,随着营养液中铵态氮比例的提高,雾培生菜生物量、叶片SPAD值、光合参数(净光合速率、气孔导度、胞间CO2浓度、蒸腾速率)、还原型抗坏血酸、谷胱甘肽、总酚、类黄酮和类胡萝卜素积累量均呈现先升高后降低的趋势；硝酸盐与可溶性糖含量逐渐降低,而可溶性蛋白、还原型抗坏血酸、谷胱甘肽、总酚、类黄酮和类胡萝卜素等抗氧化物质含量以及FRAP抗氧化活性和DPPH自由基清除率均逐渐升高。在硝铵比为0：100时,生菜叶片可溶性蛋白、抗氧化物质含量、FRAP抗氧化活性以及DPPH自由基清除率最高,但是全铵营养严重抑制了生物量的积累；而硝铵比为75：25时不仅叶片光合作用强度、生物量和抗氧化物质积累量最高,并维持较高的抗氧化物质浓度和抗氧化活性,同时显著降低硝酸盐含量。因此,综合考虑生物量、营养品质和氮素营养状况,雾培生菜生产中营养液的硝铵比以75：25为宜。(5)研究了采收前氮素供应方式(100%NO3-、50%NO3-、0%NO3-、50%NO3"+50%NH4+、50%NH4+)对雾培生菜产量、抗氧化物质含量和抗氧化活性的影响。结果表明,采收前处理3d时,不同供氮方式间雾培生菜的地上部鲜、干重、硝酸盐以及抗氧化物质含量没有显著差异。采收前处理6d以上,与持续供应100%NO3-处理相比,改变供氮方式均可显著降低生菜叶片和茎中硝酸盐含量,但停止供氮(0%NO3-)、硝态氮减半(50%NO3-)或以铵态氮为唯一氮源(50%NH4+)处理均会不同程度地降低生物量,而供应混合氮源(50%NO3-+50%NH4+)可显著提高生物量；除了停止供氮(0%NO3-)处理降低了抗坏血酸、谷胱甘肽含量外,其他供氮方式均显著提高了叶片内抗坏血酸、谷胱甘肽、类黄酮、总酚含量、FPAR值以及DPPH自由基清除率。其中,抗坏血酸、谷胱甘肽含量以50%NH4+处理最高,50%NO3-+50%NH4+处理次之；多酚、类黄酮含量则以0%NO3-处理最高,50%NH4+处理次之。因此,在采收前6d用硝铵混合氮源(50%NO3-+50%NH4+)代替NO3-可在显著提高生菜生物量的同时显著降低生菜的硝酸盐含量,并维持具有较高的抗氧化物质含量与抗氧化能力。更多还原

【Abstract】 Aeroponics is a soilless culture technique for growing vegetables and other crops in which the roots are suspended in the air and are intermittently sprayed with a nutrient solution to supply the plants with mineral and water. It provides a possible solution to the existing problems of soil-borne diseases, soil salinity in soil-based systems and oxygen deficiency in general hydroponics systems. Aeroponics is considered to be an economical and environmentally friendly modern technology for producing natural and healthy crops. It has been widely used in commercial horticultural production, spacecraft life support system and courtyard agriculture. On the other hand an optimized nutrient solution is a key determining factor of high yield and product quality of vegetable grown in aeroponic systems. Unfortunately, the nutrient solutions with high concentration of nitrate nitrogen are commonly used in present aeroponics, which not only results in raising production costs, enhancing difficulties of management, but also in high nitrate accumulation. Therefore, it is critical to elucidate the mechanism of the effect of nitrogen supply on the yield and quality of aeroponically grown vegetables. Modulating the nutrient solution of leafy vegetables in aeroponic production is scarcely reported at present. The objective of this study is selecting appropriate nutrient formulation and comparing the difference between aeroponic and hydroponic systems, and to investigate the effect of nitrogen nutrient supply on the yield, antioxidant contents and antioxidant activity and finally to determine the optimal nutrient solution management for aeroponically grown lettuce (Lactuca sativa L.), which would provide scientific basis for the production of low-nitrate lettuce with high yield and nutritional quality. The main results obtained from the experiments are summarized as follows:1. The effects of five hydroponic nutrient solutions, Hoagland formula, Japanese Yamazaki formula (JY), Japanese Garden formula (JG), South China Agricultural University (SCAU) formula B for leafy vegetables and England Hewitt formula (EH), were compared on the biomass production and nutritional quality of aeroponically grown lettuce. The results showed that the pH levels of five solutions were increased to some extent during the treatment. The highest increase in pH was observed in EH, while the lowest was in SCAU formula B. Plants grown in SCAU formula B solution showed high fresh and dry weight of roots and shoots, compared to the plants grown in other four nutrient solutions. Furthermore, SCAU formula B treated plants showed the highest ascorbic acid content, FRAP (ferric reducing/antioxidant power) value, DPPH (1,1-diphenyl-2-picrydrazyl) radical scavenging rate as well as soluble sugar content in the leaves among all nutrient solution-treated plants. However, the soluble protein content was comparable to that of JG treated plants, while the glutathione content was lower than that of JG treated plants. Furthermore the nitrate content of stems and leaves of SCAU formula B treated plants were significantly lower than those of EH and Hoagland treated plants, but a little higher than those of JG and JY treated plants. These results indicate that aeroponically grown lettuce in SCAU formula B solution produced high biomass yield, high antioxidant content and antioxidant activity, and low nitrate content, suggesting that SCAU formula B is the most ideal nutrient solution for aeroponically grown lettuce, whereas EH and JY formula are unsuitable for aeroponically grown lettuce.2. Hydroponic and aeroponic experiments were carried out to study the effects of two different cultures on the biomass production and nutritional quality of lettuce under different nitrogen levels (2,8 and 20 mmol/L). Results showed that with the increased nitrogen level, the contents of nitrate and soluble protein in the leaves and stems increased, while concentration of soluble sugar, ascorbic acid and glutathione, FRAP value and DPPH radical scavenging rate decreased in both hydroponics and aeroponics. Highest root morphology index, photosynthetic index, fresh weight, accumulation of soluble protein, soluble sugar, ascorbic acid and glutathione were observed at the nitrogen level of 8 mmol/L. Under the same nitrogen level, root growth, biomass, relative growth rate, SPAD value and photosynthesis in aeroponics were significantly higher than those in hydroponics, while glutathione and nitrate content in levels and stems in aeroponics were much lower than in hydroponics, and with similar or higher FRAP value and DPPH radical scavenging rate compared with hydroponics. Although there was no significant difference was observed in soluble sugar, soluble protein, ascorbic acid in two culture systems, but the accumulation of soluble protein, soluble sugar, ascorbic acid and glutathione in aeroponics were markedly higher than those in hydroponics. Therefore, aeroponics is beneficial for higher biomass, antioxidant accumulation and antioxidant activity, its especially apparent under the nitrogen level of 8 mmol/L.3. An aeroponics was carried out to study the effects of different nitrogen levels (4,8,12,16 and 20 mmol/L) on the biomass, antioxidant contents and antioxidant activity in lettuce. Results showed that because of increased nitrogen level from 4 mmol/L to 8 mmol/L, biomass of lettuce increased markedly, but biomass of lettuce was not affected with nitrogen level further increasing up to 12 mmol/L. When superfluous nitrogen was supplied (16 and 20mmol/L) not only decreased biomass obviously, but it also caused the highest nitrate accumulation. Furthermore, soluble sugar content in the leaves and stems decreased and soluble protein content increased firstly and then decreased slightly with nitrogen levels increasing. The contents of ascorbic acid, glutathione, total phenlics and flavonoids in leaves decreased as nitrogen levels were elevated. But when nitrogen level was increased from 4 mmol/L to 8 mmol/L, except for ascorbic acid and DPPH radical scavenging rate which decreased, there was no significant changes in the contents of glutathione, total phenlics, flavonoids and FRAP value. As biomass and nutritional quality of lettuce were taken into account, nitrogen level of 8 mmol/L might be the optimal nitrogen level for aeroponically grown lettuce.4. An aeroponics was conducted to investigate the effects of different NO3-:NH4+ ratio (100:0,75:25,50:50,25:75,0:100) on the biomass, nutritional quality and antioxidant activity in lettuce. Results showed that with the increasing proportion of ammonium in the nutrient solution, the biomasses, SPAD values, photosynthetic index and accumulation of ascorbic acid, glutathione, total phenlics, flavonoids and carotenoid increased markedly and later decreased gradually, nitrate and soluble sugar decreased, while soluble protein, ascorbic acid, glutathione, total phenlics, flavonoids, carotenoid, FRAP value and DPPH radical scavenging rate increased gradually in aeroponically grown lettuce. The highest contents of soluble protein, antioxidant contents and antioxidant activity were observed when nitrate was totally replaced by ammonium, but ammonium inhibited fresh biomass seriously. When NO3-:NH4+ratio of 75:25 was supplied, photosynthesis, fresh biomass and accumulation of antioxidant in leaves were found to be highest. This indicated that appropriate amount of ammonium (25%) could promote the accumulation of biomass and antioxidants, enhance photosynthesis ability and decrease nitrate content. Hence, NO3-:NH4+ratio of 75:25 should be optimal for NO3-:NH4+ratio for the production of both high-yield and high-quality aeroponically grown lettuce.5. An aeroponic culture was carried out to investigate the effects of nitrogen supply in the nutrient solution (100% NO3-,50%NO3-,0%NO3-,50%NO3-+50%NH4+ 50%NH4+) before harvest on biomass, antioxidant content and antioxidant activity in lettuce. Results showed that, after 3 days’treatments, there were no significant effects on fresh biomass, dry weight, nitrate and antioxidant content of aeroponically grown lettuce. After more than 6 days’treatments, nitrate content in leaves and stems were significantly reduced by all the nitrogen supply methods, compared to continuous supplying 100%NO3- continually, and biomass were reduced in treatments of 0% NO3-,50%NH4+ and 50%NO3- in a certain extent, but was significantly increased in 50%NO3-+50%NH4+. Except for the treatment of nitrate withdrawal (0%NO3-) in which ascorbic acid and glutathione content were reduced, the other treatments increased antioxidant contents and improved antioxidant activity in leaves of lettuce, and after more than 6 days’ treatment, the influence could be more and more remarkable. Highest contents of ascorbic acid and glutathione were obtained in 50% NH4+, and then in 50%NO3-+50%NH4+, and highest contents of total phenlics and flavonoids were obtain in 0% NO3-, and then in 50%NO3-+50%NH4+. It is suggested that the 100% of nitrogen concentration supplied with mixed nitrogen source (50% NO3-+50%NH4+) in the nutrient solutions 6 days prior to harvest may be suitable to produce aeroponically grown lettuce with low nitrate, high yield, antioxidant content and antioxidant activity.更多还原