Document Type : Original Research Article
Authors
1
Horticulture Department, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo, Egypt
2
Department of Agricultural Botany, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo, Egypt
3
Soils and Water Department, Faculty of Agriculture, Al-Azhar University, Nassr City, Cairo, Egypt
Abstract
Solidago virgaurea L., valued for its ornamental appeal, faces cultivation challenges due to excessive vegetative growth, hence necessitating effective control of excessive stem elongation and the need for growth management strategies. This study investigated the efficacy of cycocel (CCC) and paclobutrazol (PBZ) as plant growth regulators (PGRs) to optimize growth, flowering, and biochemical composition in potted S. virgaurea plants. A two-season field experiment was conducted in 2022/2023 and 2023/2024 using foliar applications of CCC (0, 1000, 2000, 3000 mg l⁻¹) and PBZ (25, 50, 75 mg l⁻¹) on rooted cuttings. The results showed a clear dose-dependent response, with 3000 mg l⁻¹ CCC significantly reducing plant height and promoting branching, achieving commercially desirable plant architecture. Conversely, 75 mg l⁻¹ PBZ suppressed vegetative growth. CCC treatments, particularly 1000 mg l⁻¹, advanced flowering and improved inflorescence characteristics. Both CCC and PBZ stimulated photosynthetic pigment content, with 75 mg l⁻¹ PBZ generally increasing chlorophyll levels and 3000 mg l⁻¹ CCC increasing carotenoids. Furthermore, 3000 mg l⁻¹ CCC significantly increased nutrient content (N, P, K) and total carbohydrate accumulation. Besides, cycocel and paclobutrazol significantly influence the anatomical structure of solidago leaves. High cycocel concentrations inhibited epidermal thickness and vascular development, while moderate paclobutrazol concentrations increased palisade and mesophyll thickness, indicating a potential for improved growth and increased stress tolerance, which ultimately improved the quality and productivity of the plant. Notably, moderate concentrations of CCC (2000 mg l⁻¹) and PBZ (50 mg l⁻¹) demonstrated the potential to achieve optimal plant height for market standards. Furthermore, these PGRs offer a sustainable method to improve the commercial cultivation and marketability of S. virgaurea by enhancing its ornamental quality and yield.
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