LED红蓝组合光谱下强光照射时长及频率对生菜生长及营养元素吸收的影响

红蓝光谱作为植物光合色素光吸收的最大波段，是植物光合作用的主要作用光谱，且红蓝LED已成为植物工厂的主流光源。因此为实现植物工厂的广泛应用，植物对红蓝光供光模式的响应及其机理亟待研究。在人工光植物工厂中，应用电感耦合等离子体原子发射光谱技术（ICP-AES），研究红蓝LED组合光谱下强光照射时长和频率对生菜生长及营养元素吸收的影响。研究包含两个独立试验。试验一设置5个光处理：光强为500 μmol·m-2·s-1的强光分别在常规光照（150 μmol·m-2·s-1）的光期中间照射0 h（CK），0.5 h（HL0.5），1 h（HL1），2 h（HL2）和4 h（HL4）。试验二设置4个交替光处理和1个常规光照处理（NL，170 μmol·m-2·s-1），在交替光处理中，1 h的强光（500 μmol·m-2·s-1）在光期内被分别出现1次（A1）、3次（A3）、6次（A6）和12次（A12），将光强为150 μmol·m-2·s-1的光期分成相等的时间段。两个试验中光质（4R∶1B）、光周期（16/8 h）和处理天数（20 d）相同。结果表明，试验一中生菜的地上部生物量和N，C，P，K，Ca和Mg等大中量元素累积量均表现出随强光照射时间延长先增加后降低的趋势。和CK处理相比，HL4处理下生菜的地下部干鲜重和比叶重显著提高，叶面积显著降低。HL2处理下生菜的地上部干重和N，C，P，K，Ca和Mg元素累积量均最高。在试验二中，相比常规光照，A6处理显著降低了生菜的地上部鲜重，提高了生菜的根冠比，但其他处理间生菜生物量差异不显著。强光交替照射处理显著提高了生菜碳元素含量，但是强光照射频率对生菜的干物质的量和营养元素累积量无显著影响。综上所述，在光期中间加短时间连续的强光照射能够有效提高生菜体内营养元素和生物量的累积，更适用于植物工厂内的生菜栽培。

Effects of High Light Duration and Frequencies on Growth and Nutrient Element Contents of Hydroponic Lettuce Cultivated Under LED Red and Blue Light

As the largest band of light absorption of plant photosynthetic pigment, the red and blue spectrum is the main function spectrum of plant photosynthesis, and red-blue LED has become the mainstream light source of plant factories. The response of plants to red-blue light and its mechanism needs to be explored. In this study, effects of high light duration and alternating frequencies of high light supplied with red-blue LEDs on growth and nutrient element content as well as accumulation of hydroponic lettuce were conducted using ICP-AES analysis technology in an artificial plant factory. Five treatments were set up in experiment 1: high light (500 μmol·m-2·s-1) was irradiated for 0 h (CK), 0.5 h (HL0.5), 1 h (HL1), 2 h (HL2) and 4 h (HL4) in the middle of the light period (150 μmol·m-2·s-1), respectively. In experiment 2, set up one conventional treatment (NL, 170 μmol·m-2·s-1) and four alternate light treatments, in which 1 h high light was separated into four different alternating frequencies: one time (A1), three times (A3), six times (A6) and twelve times (A12). The light quality (4R∶1B), photoperiod (16/8 h), and treatment days (20 days) were the same in the two experiments. The results showed that the biomass production and the accumulation of nutrients of lettuce such as N，C，P，K，Ca，Mg increased first and then decreased with the increase of high light duration. Compared with the CK, the root dry and fresh weight, and specific leaf weight of lettuce grown under HL4, increased significantly, and the leaf area decreased significantly. The dry weight of lettuce and the accumulation of N，C，P，K，Ca and Mg were the highest under HL2. Compared with NL treatment, A6 significantly reduced the fresh weight and increased the root shoot ratio of lettuce, but there was no significant difference among other treatments. The alternating light treatments significantly increased the C element content of lettuce, but the alternating frequencies of high light had no significant effect on the biomass production and the accumulation of nutrient elements. In conclusion, applying a short-term continuous high light irradiation in the middle of the light period can effectively improve the accumulation of nutrients and biomass production in lettuce and is more suitable for lettuce cultivation in plant factories.