Everyone has their own characteristics; some people love quiet, others love activity, and wheat has its own traits too. Winter wheat is particularly sensitive to cold in winter; it can easily freeze to death, but spring wheat is not cold-resistant. In northern China, some varieties of winter wheat can endure cold weather down to -20°C during winter. However, come spring, they become susceptible to cold just like spring wheat.
What causes this phenomenon? It turns out that the phenomenon of being cold-resistant in winter but sensitive in spring is related to the wheat’s own characteristics, growth conditions, and sugar content.
Winter wheat develops its strong cold resistance during winter, through acclimatization facilitated by the light and low temperatures it experiences in late autumn. This acclimatization process increases the sugar content within the wheat. Winter wheat is sown in autumn and starts to germinate and grow; as winter approaches and temperatures drop, it gradually wants to “sleep” and stops growing. But in early winter, the daytime temperatures are still warm, and at night they drop significantly. So, it continues to grow during the day, absorbing nutrients from the soil and synthesizing the necessary nutrients through its leaves using sunlight. The nutrients produced during the day are not completely “consumed,” and some are stored. At night, when the temperature drops, the wheat “sleeps” and stops growing. The nutrients prepared for consumption at night are stored due to decreased nighttime nutrient needs, turning into sugars, which help in cold protection due to their abundance.
Moreover, wheat is made up of numerous cells. Under a microscope, one can see that wheat leaves are composed of countless cells containing a substance called protoplasm, along with water. If the temperature drops significantly in winter, some of the water in the cells evaporates, leaving behind a more concentrated protoplasm. The concentration of protoplasm, coupled with an increase in sugar content, gives winter wheat a high level of cold resistance; thus, winter wheat is not afraid of the cold in winter.
However, as temperatures rise day by day in spring, the wheat grows rapidly both day and night. Consequently, the sugar content in the plant gradually decreases while the water content increases, diluting the protoplasm. This reduction in the concentration of protoplasm leads to a gradual decrease in the cold resistance of winter wheat. If there is even a slight frost, it can damage the wheat.
Therefore, while winter wheat is not afraid of the cold during winter, it often cannot withstand cold in spring. Thus, in spring, we should pay special attention to protecting wheat from the cold.