Abstract

Flower colour is a critical trait in ornamental plants, influencing consumer preference, ecological interactions, and commercial value. Recent scientific advances have significantly deepened our understanding of the developmental, genetic, biochemical, and environmental factors that regulate flower colour. This review highlights key progress in elucidating the complex molecular pathways and regulatory networks that control pigment biosynthesis, gene expression, and colour variation in ornamental species. The primary pigments responsible for flower coloration are anthocyanins, carotenoids, and betalains. Anthocyanins are flavonoid compounds that produce a wide spectrum of red, purple, and blue hues. Carotenoids generate yellow to orange shades, while betalains, found in specific plant families like Caryophyllales, contribute red and yellow tones. Recent studies have identified numerous structural genes involved in these pigment biosynthetic pathways, including CHS (chalcone synthase), DFR (dihydroflavonol 4-reductase), ANS (anthocyanidin synthase), and UFGT (UDP-glucose flavonoid glucosyltransferase), all of which are crucial for anthocyanin accumulation. Beyond structural genes, transcription factors such as MYB, bHLH, and WD40 proteins form regulatory complexes that modulate the expression of pigment biosynthesis genes. These transcriptional regulators have been extensively studied in model species and are now being identified in ornamental plants like petunia, chrysanthemum, rose, and hibiscus. Advances in genome sequencing and transcriptomics have accelerated the discovery of species-specific regulators and helped uncover new allelic variants linked to flower colour diversity. Genetic engineering and CRISPR-based gene editing have emerged as powerful tools for modifying flower colour in a targeted manner. For instance, silencing of specific genes in the anthocyanin pathway can result in white or pale flowers, while overexpression of pigment-promoting genes can intensify colour. Transgenic technologies have enabled the production of novel flower colours, such as blue roses and carnations, which were previously unattainable through traditional breeding. Environmental factors—including light, temperature, soil pH, and nutrient availability—also influence pigment synthesis and stability. Studies show that high light intensity and cooler temperatures often promote anthocyanin accumulation, enhancing red and purple hues. Epigenetic modifications and plant hormone signaling (e.g., abscisic acid and jasmonic acid pathways) have also been implicated in the dynamic regulation of flower colour in response to environmental cues. In addition to fundamental research, efforts are underway to apply these insights in horticulture and floriculture industries. Marker-assisted selection, metabolic engineering, and synthetic biology approaches are being used to create ornamental varieties with customized flower colours and improved colour stability. These innovations aim to meet consumer demand, extend vase life, and adapt ornamental plants to diverse growing conditions. In conclusion, recent advances in molecular biology, genetics, and biotechnology have greatly expanded our understanding of flower colour development and regulation in ornamental plants. Continued research will further unravel the intricate controls of pigment biosynthesis and enable more precise manipulation of flower traits, offering exciting opportunities for both scientific discovery and commercial innovation in the ornamental plant sector.