Transcriptome Reveals Growth Responses of Populus qamdoensis Under Blue and Green Films

<i>Populus qamdoensis</i> cuttings were treated with transparent colorless film (WF), blue film (BF), and green film (GF), and the leaf physiological indices were measured and transcriptome sequencing was performed. The results showed that BF treatment significantly inhibited the height growth, leaf length, and leaf width of <i>P. qamdoensis</i>, while significantly increasing the thickness of leaf palisade tissue, upper epidermis, and the density of leaf structure. The GF treatment increased stomatal conductance (Gs) and intercellular CO₂ concentration (Ci), while the BF treatment enhanced water use efficiency (WUE). Both BF and GF increased the contents of chlorophyll b (Chl b) and carotenoids (Car). BF treatment increased the content of total soluble sugars but decreased the contents of sucrose and starch. Transcriptome analysis revealed that under BF treatment, most genes in the sucrose and starch metabolism pathways were up-regulated, and the <i>AUX/IAA</i>, <i>GH3</i>, and <i>SAUR</i> genes in the auxin pathway also showed an up-regulated trend. In contrast, under GF treatment, most genes in the porphyrin and chlorophyll metabolic pathway were up-regulated, and most genes in the gibberellin pathway also showed up-regulation. Analysis of photoreceptor gene expression showed that GF treatment significantly up-regulated the expression of <i>HYH</i>, <i>COP1</i>, <i>CRY1</i>, <i>HY5</i>, and <i>PIF4</i> genes, while BF treatment had the opposite effect. These results provide a theoretical basis for revealing the evolutionary mechanisms underlying the adaptation of plants to different light environments.