Effects of different plant growth regulators on the cultivation of wetland irises

Wetland irises are highly valued for their vibrant flowers and strong adaptability, making them important ornamental plants with broad applications in landscaping. However, their cultivation is often constrained by inefficient propagation. The application of plant growth regulators (PGRs) in wetland irises remains limited. This study systematically examined the effects of different concentrations of 6-benzylaminopurine (6-BA; 1,000 and 2,000 mg/L), and prohexadione-Ca (PC; 500 and 1,000 mg/L) on key growth parameters of three wetland iris species: Iris ensata, Iris ensata var. variegata, and Iris sanguinea. Specifically, the study focuses on evaluating the impacts of these PGRs on bud number, plant height, rhizome diameter increment, rhizome weight, and flowering performance. Quantitative analyses of the physiological and morphological responses of these species to PGR treatments revealed distinct, species-specific responses to PGR treatments. Low concentrations of PC increased bud number by up to 0.75 and flower number by 0.47 per plant in I. ensata, while high concentrations of both regulators significantly reduced plant height and rhizome enlargement, particularly in Iris ensata var. variegata and I. sanguinea. These findings provide critical insights for optimizing cultivation practices of wetland irises and also contribute to both theoretical knowledge and practical guidelines for leveraging PGRs to improve the ornamental and functional traits of these plants in landscape applications.