The study of the regulatory mechanism of exogenous plant growth regulators (PGRs) on the relevant physiological indicators is essential to maintain the normal growth of Rosa hybrida under high-temperature conditions. The photosynthetic and physiological characteristics of the ornamental cut rose Rosa hybrida ‘Carolla’ under high temperature were studied by spraying leaves with various concentrations of exogenous salicylic acid (SA; 0.5, 1.0, 1.5, or 2.0 mmol·L⁻¹), 6-benzylaminopurine (6-BA; 10, 20, 30, or 50 μmol·L⁻¹), abscisic acid (ABA; 10, 20, 30, or 50 mg·L⁻¹), or distilled water (control). The results indicated that a foliar spray of either SA, 6-BA, or ABA could mitigate the impact of high temperatures. Compared to the control, the application of SA, 6-BA, or ABA increased the net CO₂ assimilation rate (A_n), transpiration rate (E), stomatal conductance (G_s), and water use efficiency (WUE) of ‘Carolla’, while decreasing the leaf relative electrical conductivity (REC) and malondialdehyde (MDA) content. The applications of SA, 6-BA, or ABA increased the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) and altered the proline (Pro), soluble protein, and soluble sugar contents. The results showed that foliar sprays of SA, 6-BA, or ABA could enhance the heat tolerance of ‘Carolla’ by promoting photosynthesis, cell membrane structural stability, antioxidant enzyme activity, and osmoregulation in plants under high-temperature stress. The experiment showed that 1.5 mmol·L⁻¹ SA, 20 μmol·L⁻¹ 6-BA, or 75 μmol·L⁻¹ ABA could alleviate the damage caused by high temperatures, with 20 μmol·L⁻¹ 6-BA having the best effect.

Flower color and fragrance are important traits that give ornamental plants their value. The synergistic combination of flower color and scent attracts pollinators with specific preferences. In this study, we discuss the connection between biosynthetic pathways leading to color and scent in flowers. Pigments and scent compounds in flowers vary in phenol and terpene contents, providing many combinations of color and scent. Many floral pigments and scent compounds share the same biosynthetic pathways, including the shikimate (SA), methylerythritol 4-phosphate (MEP), and mevalonate (MVA) pathways. In addition to reviewing the biosynthesis, functions, and changes in floral color and scent in relation to abiotic factors, we suggest a novel schematic diagram of the shared biosynthetic pathways in flowering plants for floral pigments and scent compounds classified as phenolics and terpenes. Although more information is still needed, it seems clear that the color and scent of flowers have a biochemical connection and are a selective choice. Therefore, a comprehensive understanding of the biochemical linkage between the color and fragrance of flowers is critical for developing new varieties with novel traits.

Scape bending is the primary cause shortening the vase life of cut gerbera flowers (Gerbera jamesonii ‘Harmony’). A previous study showed that this bending is closely related to the scape hardness, which is attributed to cell wall rigidity maintained by calcium ion bonds. In this experiment, the developing gerbera scape was sprayed with 0.5 and 1% calcium chloride to determine whether exogenous calcium directly influences scape hardness and whether it is related to pectin crosslinks. The calcium spray hardened the scape by 12% and efficiently reduced bending, thereby prolonging the vase life of the cut gerbera flowers. A 9% increase in calcium ions (Ca²⁺) was detected in the CaCl₂-treated flowers compared to the control flowers. Additionally, the pectin content increased by up to 14% in the CaCl₂-treated flowers as compared to that in the control. Pectins are the main polysaccharides of cell walls that impact plant tissue integrity and rigidity, with calcium ions acting as bonds for pectin crosslinking. Calcium treatment efficiently increased the content of total pectin in the cell walls and slowed the conversion of insoluble pectin (IP) to water-soluble pectin (WSP) during vase life. The results suggest that exogenously applied calcium increases the Ca²⁺ in cellular tissue and affects the pectin levels, which may aid in increasing the scape hardness by strengthening the calcium–pectin combination in cell walls.