Age-Dependent Flowering Transition in Cymbidium goeringii: Physiological Characterization and Small RNA Profiling

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Age-dependent flowering is a prominent feature of perennial orchids, yet its physiological and small RNA basis remains poorly understood in Cymbidium goeringii. Here, floral bud formation, carbohydrate contents, and endogenous hormones were examined across successive shoot age stages, and four representative stages were selected for small RNA sequencing. Floral bud formation showed a clear age-dependent rise-and-fall pattern, accompanied by distinct changes in carbohydrate and hormone levels. Small RNA sequencing identified 810 miRNAs, including 356 known and 454 putative novel miRNAs, of which 311 were differentially expressed. Temporal expression analysis grouped 210 DEMIs into four significant profiles, all showing reduced expression in the oldest shoots. Functional analysis of predicted targets highlighted starch and sucrose metabolism and plant hormone signal transduction, and further pathway analysis identified multiple predicted miRNA–target associations related to carbohydrate metabolism and hormone signaling. qRT-PCR analysis generally supported the sequencing-based expression patterns. These findings reveal coordinated age-related changes in flowering competence, physiological status, and miRNA expression, and identify candidate miRNAs and functional pathways potentially associated with age-dependent flowering in C. goeringii.