Leaf and Crown Cuticular Wax Responses in Annual Bluegrass (Poa annua L.) Plants Exposed to Ice Encasement

The plant cuticle, the outermost protective layer of most aboveground plant parts, serves as the first line of defence. While its role in various stress responses has been well-studied, its role in ice encasement stress tolerance is unknown. This research aimed to investigate changes in cuticular wax on the leaves and crowns of annual bluegrass after different ice encasement durations (0, 40, and 60 days) and to analyse the relationships between wax levels, malondialdehyde (MDA) content, electrolyte leakage (EL), and recovery rate. A two-year controlled environment study was conducted during 2022–2023 and 2023–2024 in East Lansing, MI, USA. Higher wax coverage was observed on leaves (61.89 μg cm⁻²) compared to crowns (7.64 μg cm⁻²). On average for leaves and crowns, the highest wax coverage was observed in the 0-day treatment (41.10 μg cm⁻²), whereas the least was observed in the 60 days treatment (27.90 μg cm⁻²). The reduction on wax coverage was primarily due to C₂₆-hexacosanol. A strong negative correlation existed between wax coverage, malondialdehyde content, and electrolyte leakage, whereas wax coverage and recovery rate were strongly positively correlated, indicating that cuticular waxes may help protect against stress damage. Future research should explore these mechanisms further to develop effective strategies for alleviating winter stress in grass species.