Cai Wenliang Wu Chonghai Chen Dejiu Li Li Li Zhenlu (Shandong Jining Seed Management Station)
Dai Meixiang (Jining City Academy of Agricultural Sciences, Shandong Province)
In the middle and later stages of wheat breeding in 2006-2007, a large area of ​​spring frost damage and late lodging occurred in the wheat fields of Jining City and the surrounding areas, causing huge losses to wheat production. As the number of effective panicles was reduced due to frost damage, the weight of 1000 grains dropped due to lodging. In order to correctly understand and solve the seed disputes caused by cold injury and lodging of wheat, according to the investigation and analysis of the causes of cold injury and lodging of wheat, talk about the relationship between cold damage and late lodging of wheat and its varieties, and measures for disaster prevention and reduction.
1 Spring frost damage and late lodging in wheat from 2006 to 2007
1.1 Spring frost damage
1.1.1 Freezing injury in early spring
Cold injury in early spring is the phenomenon that the temperature drops below the freezing point, causing the ice to be frozen in the wheat plant. On and around March 6, 2007, under the influence of strong cold air, strong winds, rainfall, and cool weather occurred in Jining City. The minimum temperature dropped below the freezing point (zero degrees) to reach -4.7 to 8.2°C. The first step was to freeze cells in the intercellular spaces of wheat plants. , The protoplasm and the liquid cell are extravasated, the protoplasmic colloids are concentrated or degenerated, the cells are dehydrated and contracted, and the cells are mechanically injured by compression. As the outside temperature continues to drop, the protoplasm of the meristem cells in the process of wheat ear differentiation will be frozen, which will denature the protoplasm and lead to cell death. As a result, the leaves and young ears of wheat plants in the long wheat field will be frozen to death.
1.1.2 Night frost damage
Late frost in South-Western Shandong Province generally occurs in the middle and early April of spring. Around April 3, 2007, due to the influence of strong cold air, the temperature dropped abruptly to around freezing point, reaching -1.3-0.8°C, forming an obvious night frost frost-damaging weather, causing freezing of cell tissue of wheat plants leading to mechanical damage and dehydration. The structure and function of the cell membrane are destroyed, the photosynthesis is blocked, and the protein in the body is degraded, resulting in the accumulation and poisoning of ammonium. Rejuvenate part of the prosperous wheat fields, causing spikelets and stamens to die of infertility. Jining and surrounding areas are the hardest hit areas of this spring frost.
1.1.3 The Main Symptoms of Frozen Wheat Fields
In the spring of two frost damages in winter, due to different terrain, wheat field location, soil type, field soil moisture, cultivation management, variety characteristics and plant growth status, the degree of frost damage in wheat fields has a significant difference. There are mainly four types: 1 only the leaves are frozen, the field shows some leaves withered; 2 young ears are frozen, although the ear can be heading, but the upper or lower spikelets are not strong, become "incomplete spikes"; 3 young ears by Freeze and dry withered, stems and leaves showed normal, some stems and stems formed "no spike stems" and the number of panicles decreased significantly; 4 the frozen main stems and big stems were freeze-dried, and the field was yellow, and the number of panicles per unit area decreased by 50 %the above.
1.2 late lodging
1.2.1 Stem lodging
That is, irreversible bending and breaking occur at the internodes of stems. Wheat stem lodging usually occurs after jointing. After lodging, the leaves overlap. Photosynthesis is severely affected. The plant tissue is not smooth, the nutrient and water flow is blocked, and the maturation is delayed, the grains are less, the grain is more grainy, and the earlier the lodging, the heavier the yield is. . The physiological causes of the lodging of wheat are the poor development of the stem. The stalks are stunted, the internodes of the base are slender, and the culm walls are thin, which is prone to lodging. The second is poor nutritional status. Large groups, lack of light, and excessive nitrogen nutrition all lead to a lack of carbohydrates, which is not conducive to the lodging of stems. The third is the change of stems during grain filling. The organic matter stored in the stalk during the grain filling stage is decomposed into a large amount and transferred to the grain, so that the mechanical strength of the stalk is weakened, thereby affecting the lodging resistance of the plant. From the late lodging period of wheat in 2006-2007, the large-scale long-grained wheat field has fallen from the booting stage, and the lodging range and degree have gradually increased, reaching the maximum value at the ripening stage.
1.2.2 Root lodging
That is, lodging occurs due to loosening of the root. There are two obvious characteristics of root lodging and stem lodging. First, the plant is not tilted. Second, it occurs later, generally from filling to maturity, and is prone to large area lodging, rather than lodging. Occurrence and lodging were mainly caused by water and wind after encountering strong winds, which resulted in the loosening of the root system and weakening of the bearing capacity. August 20-22, 2007, continuous heavy winds and heavy rain, wind 5-6, gusts 7th, causing a large area of ​​wheat root lodging, many plots fell to 60% to 80%.