Photosynthetic organisms rely on light capture and the conversion of their energy into stored photosynthetic products, light is not only an important environmental signal that affects plant growth but also provides energy for their growth and development [1]. In the first step of photosynthesis, the plant’s photosynthetic pigments intercept the light signal and transfer it to the reaction center of the two light systems, Photosystems II and I (PSII, PSI), which constitute the photosynthetic unit. The quality and wavelength of light play a crucial role in influencing the photosynthetic process in plants [2,3]. Several published studies have revealed that light quality affects seed germination [4], circadian rhythm [5], axillary bud growth [6], morpho-physiological [7], secondary metabolite synthesis network [8], the ultrastructure of chloroplasts and anatomical structure of leaves [9], disease resistance [10], anthocyanin biosynthesis [11] and gene expression [12]. Studies conducted by Eze Pojmann-Ezeonyilo have demonstrated that the quality of light can impact pest biology, thereby suggesting that light quality could be a valuable tool for pest management [13]. Different light qualities can cause different physiological and metabolic responses in plants, leading to different growth states of plants. Blue light increases the photosynthetic rate and promotes stomatal opening [14]. The study of [15] has revealed that green sensors can regulate the growth of plants, in addition to red, far red, blue, and ultraviolet (UV) sensors. In this article, blue, green, white, red, and far red are represented by B, G, W, R, and FR, respectively.

The supplemental lighting and an increase in the photosynthetic daily light integral are often used to improve harvest in the process of agricultural production. Photobiological studies have revealed that the use of blue-violet light with a wavelength of 400–480 nm is conducive to improving the efficiency of photosynthesis and the protein content of crops. Exposure to B or R light, or a combination of both, enhances the expression of potassium transporter genes, leading to increased potassium uptake and accumulation. This results in enhanced lycopene synthesis and improved color of tomato fruits [16]. Exposure to B or R light, or a combination of both, enhances the expression of K transporter genes, leading to increased potassium uptake and accumulation. This results in enhanced lycopene synthesis and improved color of tomato fruits. Several methods have been adopted to mitigate the reduced yield caused by different light conditions, including breeding varieties with altered developmental responses. Compared with these methods, light-emitting diode (LED) lighting is increasingly being used for greenhouse crop cultivation because of its long service life, low energy consumption, and low heat output [17,18]. The role of auxiliary lighting has been demonstrated in numerous studies of watermelon, chrysanthemum, mustard, roses, and Brassica rapa ssp. Chinensis [19–23]. Changes in the ratio of R to B light in irradiated lettuce can increase the contents of sugars and phenols in its leaves and increase its yield [24]. Yu et al. [25] use m-MeOPTCDA converters to convert yellow-green light (510–580 nm) of sunlight into blue-violet light and red-orange light that can be absorbed by plant leaves to improve the photosynthetic efficiency of crops. Adding R light to lettuce and other leafy plants can control their plant structure. The addition of R light can reduce leaf decline and internode elongation, further, slow down plant aging and increase plant yield [26]. Prolonged exposure to certain plants, such as tomatoes and bell peppers, can improve fruit quality and yield [27,28]. At present, the research and application of light-quality control in vegetable cultivation and flower cultivation are more and more extensive, but research on the impact of light quality on tree breeding is scarce. Therefore, it is crucial to investigate how tree seedling growth and photosynthesis respond to different light qualities.

Populus trinervis is native to China and was first found in Sichuan Province. Most of them are found at altitudes between 2100 and 3000 meters. Its leaves are 2.5–5 cm wide and 4–7 cm long [29]. P. trinervis plays an irreplaceable role in the ecological balance of boreal and temperate forests. They can grow in environments such as riparian forests and provide a habitat for wild animals. So, it is very adaptable to the environment. As the altitude increases, UV light enhancement in natural light, the proportion of short wavelengths represented by B light usually has noteworthy effects on plant growth and adaptation. However, there are limited studies on the response of P. trinervis to light quality in high-altitude mountains, the changes in the photosynthetic physiology of P. trinervis under different light-quality environments is not clear, and its adaptability to different light quality is not well understood.

B light, G light, R light, and FR light occupy a large proportion of the relative content of visible light in the middle and high-altitude areas where P. trinervis grows [30]. In the present study, we focused on the influence of B light and G light on the growth of P. trinervis and measured the absolute leaf growth and photosynthetic response parameters of poplar cuttings under different light qualities. The study is expected to provide a theoretical basis and a reference for further exploring the introduction and cultivation of different poplar species in high-altitude areas.

Light is a crucial element for the growth of plants photosynthesis, it has a crucial impact on plant morphogenesis and material synthesis [35–37]. A close relationship has been found between photosynthesis and biosynthesis and the accumulation of photosynthetic products [38,39]. Adaptation of leaf photosynthesis to irradiance is influenced by B light for higher plants. B light affects plant growth in several ways [40–42]. In addition, B light photoreceptors mediate the photomorphogenesis response [43,44]. Therefore, reasonable light conditions are essential to optimize the accumulation of phytochemicals.

Pigments such as chlorophyll, carotenoids found in chloroplasts absorb, convert, and transfer light energy, affect photosynthetic response and the stomatal opening, and regulate plant morphogenesis. The quality of light can influence plant photosynthesis by altering the content and composition of chlorophyll. Kai et al. observed that strawberry cultivated under various colored plastic films showed variations in their growth, the order of treatment was as follows, according to the Chl content from highest to lowest: RF > white film > YF > green film > BF [45]. However, research conducted by Kobayashi demonstrated that exposing lettuce leaves to B light led to a higher chlorophyll content in comparison to leaves exposed to R light [46]. A similar finding was reported at Toona sinensis seeding [47]. We found that P. trinervis plants had lower levels of Chl a, Chl b, and total Chl under W light in comparison to B and G light. The results are consistent with those obtained on peas, grapes, and cotton, in which exposure to light B resulted in a rise in the chlorophyll levels of the plants [39,48,49]. Another study revealed that B light still affected Chl biosynthesis in the absence of any other lights [50]. Research on phalaenopsis also revealed that B light is beneficial for the accumulation of Chlorophyll [51]. Based on our results, B light appeared to motivate the accumulation of Chl and Car in P. trinervis.

Different plant species exhibit varying responses to different qualities of light, B light typically has a more pronounced impact on growth. In this study, the observations revealed a notable growth. in the absolute growth volume of P. trinervis seedling height and leaf length under B light. Heo et al. found that Marigold and Salvia plants had a greater height when exposed to B light compared to plants grown under W light [52]. Moreover, as a result of B light, leaf length grew significantly faster than under W light. According to Macedo and Leal-Costa, when B light was utilized, the light treatments caused Alternanthera brasiliana (L.) Kuntze produced the largest leaf area [53] and Nafiseh found the same phenomenon in Arabidopsis thaliana [54]. Our results proved that P. trinervis seedlings’ height was also significantly affected by light quality in terms of their morphological and photosynthetic features. Compared with W light, the height of plants growing under G light increased significantly. Ke et al. found that using G light resulted in a higher leaf length/width ratio, producing longer and narrower leaves compared to using W light [55]. Furthermore, we noted the following G light promoted the lengthening of leaves in P. trinervis plants. Similarly, the absolute growth of seedling height, stem diameter, leaf length, and petiole length under G light was the greatest, which was contrary to the report of Su that G light had a counteractive effect on plant growth [56]. The results on the impacts of monochromatic wavelength lights, as presented in this study, align with those previously reported by Wang et al. for cucumber plants, and by Yu et al. for Acacia mangium seedlings [56,57].

Our results indicated that Tr increased under G and B light in comparison to the W light, which was in agreement with the P_N and g_s. Yang observed a decrease in P_N under the B light of tobacco [58]. This precisely aligns with the absorption spectra of photosynthetic pigments, Chl absorbs light in the 400–500 nm wavelength range. However, Yu et al. found that the P_N level under G light was the lowest [59], contrary to our findings, which may be due to the great diversity among species. Therefore, under the same light intensity, the P_N of the plant will be different under different light qualities.

Carbohydrates can regulate plant photosynthesis, growth, and development through a feedback mechanism. Our research showed that the accumulation of total sugar and sucrose content was noteworthily influenced by B light. A significant accumulation of reducing sugars and total sugars was induced by the G light. While amylum showed the highest content under W light. It was in agreement with Wang et al.’s findings [58], that the total soluble sugar content of cucumber reductions was significant in the plants under G. Therefore, our study suggests that B and G light facilitate the biosynthesis and accumulation of soluble sugars. The Calvin cycle enzymes may be more acute under B light due to a higher rate of activity. Ke et al. also discovered that plants exposed to B light exhibited increased Rubisco carboxylase activity and higher expression of genes related to the Calvin cycle enzymes [55,58].

Through regulating the ratio of PSI and PSII, plants can acclimatize to different light environments [59]. Different monochromatic light reduced the Fm of P. trinervis leaves, but increased the NPQ compared to W light. This corresponds to the change in P_N of P. trinervis under different light qualities. This may be because plants that grow under B light conditions maintain a higher P_N to avoid damage to photosynthetic organs since B light is more energetic. Besides losing more energy by dissipating heat from the PSII reaction centers, plants grown under G light conditions also exhibit lower photosynthetic capacity [60]. Past research has demonstrated a correlation between F₀ and Chl content [61]. This study revealed that the various colors of light did not have a notable impact on the F₀ of P. trinervis, this suggests that different monochromatic lights do not significantly damage the reaction center of P. trinervis PSII compared to W light. The Fm of plants cultivated in various monochromatic light conditions. was inferior to plants grown on W light. This suggests that populus grown under W light conditions exhibited a greater degree of the Redox Potential of the Primary Plastoquinone Electron Acceptor QA in Photosystem II status than under B and G light conditions. Fv/Fm remained in a stable area when populus were grown in favorable environments, but it decreased when plants were grown in unfavorable environments [62]. No significant difference was observed between Fv/Fm under different monochromatic light and W light. This may be the result of the fact that monochromatic light is not detrimental to the growth of P. trinervis. ΦPSII is usually associated with photosynthetic efficiency and electron transfer efficiency [63], The findings indicated that plants exposed to various monochromatic lights did not exhibit significant differences from those under W light, which is in line with the change in q_p.

The findings indicated that various types of lighting had a significant impact on the growth and maturation of P. trinervis. Compared with the W light, Chl and Car accumulation and absolute plant growth of P. trinervis were significantly increased under B and G light. The effect of photosynthetic pigment accumulation was more obvious under B light. However, the absolute growth parameters such as seedling height and ground diameter were more obvious under G light. This study demonstrated that both B and G lights had noteworthy impacts. on the photosynthesis of P. trinervis. Light qualities also had an obvious effect on the accumulation of sugar content. B light mainly encouraged the accumulation of total soluble sugar and sucrose content, the accumulation effect of reducing sugar and total soluble sugar was more obvious under G light. Moreover, the influence of light characteristics on Chl fluorescence parameters of P. trinervis was primarily demonstrated by the rise in NPQ and the decline in Fm. Having insight into how spectral quality influences fundamental poplar growth parameters is crucial for comprehending both the natural and controlled development of plants.