采收前连续光照光质对三种供氮水平的水培生菜营养元素含量的影响

Effects of Continuous Light Before Harvest on Nutrient Element Contents of Hydroponic Lettuce Cultivated Supplied With Three Nitrogen Levels and Two LED Red and Blue Light Qualities

红蓝复合光是植物生长发育最有效的光谱组合,且红蓝光LED成为植物工厂进行水培叶菜生产的主流光源。采收前进行LED红蓝光连续光照具有增产和提高品质的作用,在植物工厂水培叶菜生产中具有应用前景。在植物工厂中应用水培方法和ICP-AES分析技术,研究了采收前LED红蓝光连续光照(CL)光质对三种供氮水平下水培生菜干物质累积和营养元素含量和累积量的影响。在光强150μmol·m^-2·s^-1下,试验设置了8, 10和12 mmol·L^-1三种供氮水平(N8, N10和N12),并在采收前3天设计了2种红蓝光质(2R∶1B和4R∶1B)的连续光照处理,光强为150μmol·m^-2·s^-1。结果表明,增加供氮水平可促进水培生菜地上部干重增加,采收前三天红蓝光CL后生菜地上部干重增加。供氮水平对生菜N, C和P含量无显著影响,而供氮水平的增加提高了Ca和Mg含量,但K, Fe, Mn, Cu和Zn含量却随氮水平升高呈现出降低的趋势。生菜地上部中N, Ca和Mg的累积量随供氮水平的增加而提高,但C, K, P和Fe的累积量与供氮水平无关,而微量元素Mn, Cu和Zn随氮水平升高呈现降低趋势。除C以外,其他营养元素含量和累积量均受采收前三天CL红蓝光质和供氮水平的共同影响。N浓度水平N10和N12条件下,红蓝光4∶1连续光照更有利于获得较高的营养元素含量和累积量。CL处理显著提高了生菜干物质中C的含量,但降低了K, P和Fe含量,对N, Ca, Mg, Mn, Cu和Zn的含量无显著影响;CL增加了N, C, K, P, Ca和Mg的累积量,但不影响微量元素的累积量。总之,高氮肥供给有利于提高水培生菜干物质产量和Ca和Mg含量和累积量。高氮水平下辅以LED红蓝光4∶1连续光照有利于增加较高的营养元素含量和累积量。CL处理提高了生菜干物质中C的含量,增加了N, C, K, P, Ca和Mg的累积量,但对微量元素的累积量无影响。高氮肥和采收前红蓝光CL可提高多数大中量营养元素的含量与累积量。

Red light and blue light are the main active spectra for plant photosynthesis and photomorphogenesis,also red and blue light LEDs have been the dominant light sources for hydroponic leafy vegetable production in plant factory.It is suggested that continuous light(CL)of red and blue light before harvest can improve the yield and quality of hydroponic leafy vegetables.In this study,effects of nitrate levels supplied and 72 h continuous light before harvest with the red and blue light on shoot dry weight and nutrient element content as well as accumulation were conducted using hydroponic method and ICP-AES analysis technology.Three nitrate levels(8,10 and 12 mmol·L^-1,N8,N10 and N12)and two light qualities(2R∶1B and 4R∶1B)of 150μmol·m^-2·s^-1 were designed.The results showed that shoot dry weight increased with supplied nitrate level,and CL also improved shoot dry weight.Nitrate level did not alter N,C and P contents in lettuce shoot.However,Ca and Mg contents were improved with nitrate level increment,also K,Fe,Mn,Cu and Zn contents were decreased with the increase of supplied nitrate level.Moreover,nitrate level did not alter C,K,P and Fe accumulation in lettuce shoot.However,N,Ca and Mg accumulation were improved with nitrate level increment,also Mn,Cu and Zn accumulation were decreased with the increase of supplied nitrate level.Except for C element,contents and accumulation of other nutrient elements were subjected to nitrate levels and CL light qualities.Under N10 and N12 conditions,CL with 4R∶1B is easier to obtain relatively high nutrient element content and accumulation.Through CL,C content in lettuce shoot was improved,but K,P and Fe contents were decreased,and N,Ca,Mg,Mn,Cu and Zn contents did not change significantly.However,CL promoted N,C,K,P,Ca and Mg accumulation in lettuce shoot,but did not alter microelement accumulation.In summary,high nitrate level and CL before harvest with 4R∶1B spectrum facilitates high dry shoot yield of hydroponic lettuce and high contents and accumulation of most major and medium nutrient elements.