人工霜箱的控制试验表明 ,冬小麦叶片冻结后是否受到伤害取决于最低叶温。拔节后第 1～2 0天 ,叶片的霜冻临界叶温由 - 6.5℃提高到 - 4 .5℃。幼穗是否受伤与最低叶温的关系相当密切 ,同期幼穗轻度伤害的临界叶温由 - 8.3℃提高到 - 3.9℃ ,幼穗严重伤害的临界叶温由 - 8.3℃提高到- 5.4℃。建立了叶受害、穗轻伤、穗重伤的临界叶温随拔节后天数而变的数学表达式 ,为霜冻预报和防御提供判断标准 Artificial frost box control tests show that the freezing of winter wheat leaves after injury depends on the minimum leaf temperature. From the first day to the 20th day after jointing, the critical leaf frost temperature increased from-6.5 ℃ to -4.5 ℃. The relationship between the injury of young ears and the minimum leaf temperature was quite close. The critical leaf temperature of mild injury of young ears increased from-8.3 ℃ to - 3.9 ℃ in the same period, and the critical leaf temperature of severe injury to young ears increased from-8.3 ℃ to -5.4 ℃ . The mathematical expressions of critical leaf temperature with leaf damage, slight injury of ear and severe injury of spike, which change with the number of days after the jointing, are established to provide a criterion for frost forecast and defense