The Adaptation Mechanisms of Xerophytes: from Morphological Remodeling to Molecular Regulation

NTRODUCTION: Osmanthus fragrans ‘Gui Zi’, a hermaphroditic cultivar of the Asiatic sweet olive group, exhibits a multi-season flowering habit. However, the regulatory mechanisms underlying flower development across different seasons remain unclear. Flower bud differentiation and floral organ development are crucial for ornamental traits and reproductive success, yet seasonal variations in these processes in hermaphroditic genotypes are poorly understood. RATIONALE: This study aimed to systematically compare the flower bud differentiation, flowering dynamics, and morphological development of pistils and stamens in ‘Gui Zi’ across autumn, winter, and spring seasons. The research seeks to elucidate the seasonal plasticity of floral development and explore the environmental adaptation strategies of flower organs in a multi-season flowering woody plant. RESULTS: The floral development of ‘Gui Zi’ showed significant seasonal variation. In autumn, flower bud differentiation lasted approximately 79 days, with normal development of both pistils and stamens, resulting in fertile flowers. In contrast, winter and spring flower bud differentiation was markedly shorter (34–47 days), accompanied by extended flowering periods. During these cooler seasons, stamen petaloid transformation occurred frequently (31.25% in winter and 92.59% in spring), along with varying degrees of pistil degeneration. Pistil abortion and abnormal ovule development were initiated during the carpel differentiation stage of flower bud differentiation. These findings suggest that low temperature is a key environmental factor driving floral organ malformation and reproductive organ abortion. CONCLUSION: This study reveals that the hermaphroditic cultivar ‘Gui Zi’ employs distinct flowering strategies across seasons: autumn flowering follows a complete and fertile developmental pathway, whereas winter and spring flowering is characterized by accelerated but often incomplete organ development under low-temperature conditions. The results provide important insights into the seasonal regulation of multi-season flowering and enhance our understanding of floral plasticity as an adaptive response to environmental cues in woody ornamentals.