LED红蓝光连续光照及其光强对生菜生长及矿质元素吸收的影响

红光和蓝光是植物进行光合作用和光形态建成的主要光谱，且红蓝LED是植物工厂光源的发展趋势。因此为实现连续光照在植物工厂中的应用，植物对红蓝光谱连续光照的响应特征及其机理亟待探究。在环境可控的植物工厂内，应用ICP-AES技术，研究了红蓝光谱下连续光照及其光强对生菜生长和矿质元素吸收的影响。该研究共包含两个试验，试验一设置了常规光照（12 h/12 h）和连续光照（24 h/0 h）2个光照处理及5个生菜品种，试验二设置了5个连续光照光强处理（80，120，160，200和240 μmol·m-2·s-1）。结果表明，连续光照30 d内生菜的干重和干物质含量能够持续显著提高，且表现为随连续光照光强增加而升高的趋势。但地上部鲜重仅在连续光照的前15 d得到显著提高，并随光强增加而升高。而连续光照30天时，连续光照对生菜地上部鲜重无显著促进作用，甚至显著降低意大利生菜的地上部鲜重。相比常规光照，连续光照30 d显著降低了生菜的Ca，Mg，Fe，Mn，Cu和Zn含量，但这些元素积累量均有所增加。不同光强下，生菜Ca，Fe，Cu和Zn的含量随光强增加而降低，其中Ca和Fe积累量随光强增强而升高，Cu和Zn积累量不受光强影响。Mg元素含量和积累量均随光强增强先升高后降低。Mn元素含量受光强影响不显著，但积累量随光强增大而升高。此外，连续光照30 d生菜叶片出现褪绿萎黄的伤害症状，且伤害症状随光强增加而逐渐加重，说明矿质元素含量的降低在一定程度上加剧了连续光照伤害。综上所述，15 d连续光照能够显著提高生菜产量。全生长期（30 d）连续光照虽能促进生菜干物质累积，但对产量无显著促进作用，同时还会导致生菜矿质元素含量的降低及叶片伤害。相对而言，低光强（80和120 μmol·m-2·s-1）连续光照对生菜无明显伤害作用，且矿质元素含量相对较高，但不能提高产量。研究结果表明短期红蓝光连续光照更适宜应用于在植物工厂生菜栽培，能够获得相比能量投入更高的产量。矿质元素含量的降低可能是长期连续光照伤害的机制之一。

Effect of Continuous Red/Blue LED Light and Its Light Intensity on Growth and Mineral Elements Absorption of Lettuce

Red light and blue light are the main spectra of photosynthesis and photomorphogenesis in plants, and also is a developing tendency of light source in plant factory. Therefore, to realize the application of continuous light in plant factory, the response characteristics and mechanism of plants to continuous light in red and blue spectra need to be explored. The effect of continuous light and its intensity on the growth and mineral elements absorption of lettuce was investigated by ICP-AES technology in an environmental-controlled plant factory. Five lettuce cultivars were cultivated under normal light(12 h/12 h) and continuous light (24 h/0 h) in experiment 1, and grown under continuous light with five light intensity(80，120，160，200 and 240 μmol·m-2·s-1) in experiment 2. The results showed that dry weights and dry weight ratios of lettuce significantly increased during 30 days’ continuous light, and increased with light intensity. However, continuous light only enhanced fresh weight in first 15 days, which also increased with light intensity. 30 days’ continuous light had no positive effect on fresh weight, even significantly reduced the fresh weight of Yidali cultivar. Compared with normal light, 30 days’ continuous light significantly reduced the Ca, Mg, Fe, Mn, Cu, and Zn contents, but slightly or significantly enhanced the accumulation of these mineral elements. Under different light intensity, the contents of Ca, Fe, Cu, and Zn decreased with light intensity, the accumulation of Ca and Fe increased with light intensity, while that of Cu and Zn were not affected by light intensity. Content and accumulation of Mg increased first and then decreased with the increase of light intensity. The content of Mn element was not significantly affected by light intensity, but the accumulation increased with the increase of light intensity. In addition, 30 days’ continuous light induced severe leaf chlorosis and necrosis, and this negative effect aggravated with light intensity, which indicated that the decrease of mineral element content aggravated the injury of continuous light to some extent. In conclusion, 15 days’ continuous light could enhance lettuce yield remarkably. However, although 30 days’ continuous light improved the dry weight, it had no positive effect on yield and induced the decrease of mineral elements contents and leaf injury. Even though lettuce plants grown under continuous light with low light intensity (80 and 120 μmol·m-2·s-1) had no leaf injury and relative higher mineral elements contents, it had no positive effect on yield. This study indicated that short-term continuous light is more suitable for the cultivation of lettuce in the plant factory, and can obtain higher yield than energy input. The decrease of mineral element content may be one of the mechanisms of long-term continuous light injury.