Strategies to Avoid Freezing in Plants: A Focus on Spray-Based Methods and Cuticular Wax

Ice nucleation in plants (intrinsic and extrinsic) is a broad research topic, which covers both avoidance and tolerance strategies. Our review is focused on avoidance strategies against late spring frosts that will increasingly impact both fruit trees and herbaceous plants as climate change becomes more extreme. Most active frost protection methods are dependent on sprinkler irrigation, heaters, and fans, however these practices are often expensive, environmentally damaging, or may lose effectiveness under certain freezing conditions. Here, we review and comment on the efficacy of alternative spray-based strategies including bactericides, insulators, cryoprotectants, ice nucleation inhibitors, bio-stimulants, anti-transpirants, and hydrophobic films. Adjusting hormonal and genetic factors involved in cuticle development may also enable actively growing plants to become more freeze-resistant by blocking extrinsic nucleation and preventing damage. The cuticle is the first line of defense for many abiotic and biotic stresses, and strengthening this barrier for multi-stress resistance should be further investigated.