Physiological and transcriptomic analyses reveal the regulatory mechanisms of floral response to drought stress in Camellia oleifera

Camellia oleifera is highly vulnerable to drought during flowering, yet the physiological basis of floral sensitivity remains unclear. We compared two cultivars, ‘Huashuo’ and ‘Huaxin’, under progressive drought using integrated physiological measurements and transcriptomics. Drought markedly impaired floral-bud development, with ‘Huaxin’ showing more severe necrosis and reduced pollen viability. Both cultivars exhibited decreased relative water content and increased lipid peroxidation, while ‘Huashuo’ maintained higher activities of CAT, POD, and SOD and higher levels of SS, SP, and Pro than ‘Huaxin’. Hormone profiling showed ABA and GA₃ increases in both cultivars; IAA decreased in ‘Huashuo’ (with a clear decline at the later stage) but increased in ‘Huaxin’. CTK responses diverged between cultivars—rising in ‘Huashuo’ and falling in ‘Huaxin’—whereas SA rose transiently in ‘Huaxin’, and JA displayed a transient rise in ‘Huaxin’ and a later decline in ‘Huashuo’. Physiological and hormonal indicators correlated with drought-induced floral damage, and a membership-function–based index confirmed the superior drought tolerance of ‘Huashuo’. Transcriptome sequencing identified 132,479 unigenes and 25,656 differentially expressed genes; WGCNA highlighted 41 genes linked to floral development, including 18 candidates potentially regulating floral organogenesis under drought. These results refine the floral-stage drought-response model in Camellia oleifera and provide targets for breeding drought-resilient germplasm.