Pre-anthesis light signaling of sheathed embryonic barley inflorescences defines floral fate

The pre-anthesis embryonic inflorescence greening (PEIG) is a distinctive developmental feature in the members of the Triticeae such as barley, wheat and rye. In barley (Hordeum vulgare L.), floral survival and fertility are major determinants of grain yield, yet the physiological processes supporting early inflorescence development remain poorly understood. Here, we investigated PEIG, a light-dependent chlorophyll accumulation occurring while immature inflorescences are still enclosed by leaf sheaths, and its role in overall inflorescence development. Using chlorophyll autofluorescence imaging and chlorophyll quantification, we found that PEIG in barley initiates at a surprisingly early developmental stage, when developing spikes are still enclosed by leaf sheaths. PEIG first appears in the central rachis and then progressively spreads to the spikelet primordia and other floral organs. Using a non-destructive dark treatment method designed for preventing light exposure to developing inflorescences, we further demonstrated that the inhibition of PEIG does not affect floral initiation but significantly reduces floral survival and pollen viability, particularly in the tip region of the inflorescence, indicating a critical role of light mediated PEIG in floral fate. Finally, analysis of natural variation for PEIG revealed a strong positive correlation between PEIG and floral survival. Our findings establish PEIG as an underappreciated hidden trait that supports floral viability and reproductive success, with implications to enhance grain yield potential in cereals.