三种园林植物对夜间光照的响应与适应特征

光污染是城市生态系统中重要的污染类型,目前的研究集中在光污染对人类健康、昆虫生活史、生活习性、活动规律等方面,对植物生理生态的效应研究则较少。以凤仙花(Impatiens balsamina)、小叶栀子(Gardenia jasminoides)、夏菊(Dendranthema morifolium)为研究对象,研究白光LED灯从每天18:00—24:00照光(T1处理)、每天18:00—次日8:00照光(T2处理)以及自然光周期(CK)等3种光环境条件下,3种植物生物量积累与分配、开花特征、色素含量、碳氮含量及其比值(C/N比)、抗氧化酶等方面的响应与适应特征。结果表明,T1和T2处理增加了凤仙花的生物量(分别为CK的1.4和1.9倍),降低了叶片和茎的N含量,增加了叶片的C/N比(分别为CK的1.2和1.9倍),降低了叶片的色素含量;T1处理延迟了凤仙花的花期,T2处理条件下凤仙花不开花。T1和T2处理虽然没有影响小叶栀子的花期,但增加了花的数量,减小了花的平均重量,花的C/N比显著增加(T2处理为CK的1.3倍);T2处理降低了小叶栀子叶片的叶绿素a、b及总叶绿素含量,增加了丙二醛的含量(T2处理为CK的1.7倍)。夏菊的生物量及生理特征受到T1和T2处理的影响最小,但T1和T2处理均抑制了夏菊开花。这些结果表明凤仙花和夏菊开花对光污染引起光周期的变化比较敏感,凤仙花的生长和养分特征也受到夜间光照的显著影响,光污染对小叶栀子的叶片造成了显著伤害。总的来讲,与T2相比,T1处理对3种植物的负面影响较小,在城市照明的管理过程中,可以根据需要缩短夜间光照的时间,既可以节约能源,又可以减小对植物生理生态的负面影响。

Responses and adaptive status of three garden plants exposed to night illumination

Light pollution is one of the most serious pollutants in urban ecosystems. Existing research in this field has mainly focused on the effects of light pollution on human health, life cycles, and behavior and actions of insects or other animals, whereas information regarding its effects on the physiology and ecology of plants is lacking. We used Impatiens balsamina, Gardenia jasminoides, and Dendranthema morifolium to document biomass accumulation and allocation, blossoming, pigmentation, C and N content (and C/N ratio), and activities of antioxidant enzymes in response to night illumination produced by a white LED from 18:00 to 24:00 (T1 treatment), from 18:00 to 08:00 the following day (T2 treatment), and natural photoperiod (control; CK). The main results were as follows:(1) Compared to CK, T1 and T2 increased the biomass of I. balsamina by 1.4 and 1.9 times, respectively, and the C/N ratio in leaves by 1.2 and 1.9 times, respectively, but decreased the N content in leaves and stems, and content of pigments in leaves. The T1 treatment delayed florescence, and the T2 treatment inhibited flowering. (2) Although neither T1 nor T2 affected the florescence of G. jasminoides, night illumination increased the average number of flowers and decreased average weight per flower. Compared to CK, T2 significantly increased the C/N ratio in flowers and content of malondialdehyde (MDA), although it decreased chlorophyll a, b, and total chlorophyll content in leaves. (3) Biomass and physiological traits were not obviously affected in D. morifolium. However, both T1 and T2 inhibited flowering. These results indicated that flowering of both I. balsamina and D. morifolium were sensitive to the altered photoperiodism induced by nighttime illumination. In addition, growth and nutrient status of I. balsamina was negatively affected by nighttime illumination, and there was a detrimental effect on the leaves of G. jasminoides. Generally, when compared to T2, the T1 treatment exerted fewer negative impacts on the three species. Therefore, in urban light management, we should shorten the duration of illumination to the degree it is practical. This will not only save electric energy, but also lessen the negative influence on the physiology and ecology of garden plants.