Studies on frost injury to wheat. IV.* Freezing of ears after emergence from the leaf sheath

Abstract

Internal and external factors which may influence the survival of emerged wheat ears during radiation frost were examined by a number of experiments in a freezing chamber. Hardening, stage of ear development, supercooling and cultivar were the internal factors studied in ears protected from external ice nucleation by enclosure within polyethylene bags. Neither hardening nor stage of ear development had any effect on freeze resistance. Spikelet survival was unaffected by supercooling. Variation in internal ear resistance was revealed among 16 cultivars frozen at –3.9°C. Removal of the cuticular wax coating over the unprotected ear reduced its ability to survive at –3°C in an atmosphere abundant in ice nuclei. This supports the proposal that hydrophobic wax coatings may be important in the field in protecting floral parts from external ice nucleation. The implications of these findings with respect to frost resistance in the field are discussed. _____________________ *Part III, Aust. J. Agric. Res., 17: 601 (1966).