GLR channels are required for rhythmic scent emission in Phalaenopsis bellina

Phalaenopsis bellina emits floral monoterpenes in a diurnal pattern regulated by light and circadian rhythm. Here, distinct low-frequency oscillations with a dominant peak at 1.563-1.953 mHz were recorded as floral electrical signals during monoterpene emission, and these were further resolved into well-defined diurnal rhythmic patterns. Elevated cytosolic calcium ion (Ca²⁺) in floral tepal cells was specifically associated with scent emission in P. bellina. Application of Ca²⁺ channel blockers abolished electrical signals, suppressed monoterpene emission, and downregulated the expression of the key biosynthetic enzyme gene PbGDPS. We identified four floral glutamate receptor-like channels (GLRs), among which PbGLR3.2 and PbGLR3.6 were localized to the plasma membrane and highly expressed in floral organs. Their transcript levels correlated positively with PbGDPS and relevant transcription factors. RNA interference knockdown of either PbGLR3.2 or PbGLR3.6 significantly reduced both monoterpene biosynthesis and the floral volatile emission. These findings identify PbGLR3.2 and PbGLR3.6 as essential regulators of rhythmic floral scent, a process associated with light-induced electrical and Ca²⁺ signals. Together, this work reveals a mechanistic link between floral electrophysiology, Ca²⁺ dynamics, and volatile-based ecological signaling, providing insights into how plants may optimize pollinator interactions.