The Relationship between the Spring Wheat Freezing Damage and Late Lodging and the Varieties and the Technology of Disaster Prevention and Mitigation
Cai Wenliang Wu Chonghai Chen Dejiu Li Li Li Zhenlu (Jining City Seed Management Station, Shandong Province)
Dai Meixiang (Jining Academy of Agricultural Sciences, Shandong Province)
In the middle and later stages of wheat growth in 2006-2007, a large area of ​​spring frost damage and late lodging occurred in wheat fields in Jining and surrounding areas, causing huge losses to wheat production. The number of effective ears decreased due to frost damage, and the thousand-grain weight decreased due to lodging. In order to correctly understand and resolve the seed disputes caused by wheat freezing damage and lodging, based on the investigation and analysis of the causes of wheat freezing damage and lodging, let us talk about the relationship between the spring freezing damage of wheat and the later lodging and varieties and measures for disaster prevention and mitigation.
1 The situation of wheat frost damage in spring and late lodging in 2006 ～ 2007
1.1 Freezing damage in spring
1.1.1 Frost damage in early spring
Early spring frost damage refers to the phenomenon that the temperature drops below freezing point, causing the freezing of wheat plants and damage. Around March 6, 2007, due to the strong cold air, Jining City experienced strong winds, rain, and cooling weather. The minimum temperature fell below the freezing point (zero degrees), reaching -4.7-8.2 ° C, first freezing the cell gap of wheat plants , The extravasation of the protoplasts and fluid cells, the colloids of the protoplasts are concentrated or denatured, and the cells are dehydrated and contracted, causing mechanical crushing damage to the cells. Due to the continuous decrease of the external temperature, the protoplasts of meristematic cells freeze during the wheat ear differentiation process, which denatures the protoplasts and causes cell death. As a result, the leaves and young ears of wheat plants in Wangchang wheat field are frozen and died.
1.1.2 Late frost damage
Late frost damage in southwestern Shandong generally occurs in the first and middle of April in spring. Around April 3, 2007, due to the impact of strong cold air, the temperature suddenly dropped to about freezing point, reaching -1.3-0.8 ℃, forming a clear late frost damage weather, which caused the wheat plant cell tissue to freeze causing mechanical damage and dehydration , The structure and function of the cell membrane are destroyed, photosynthesis is blocked, and the protein in the body is degraded, and ammonium accumulation and poisoning occur. Part of the flourishing wheat field suffered frost damage again, resulting in freezing and infertility of spikelets and stamens. Jining and surrounding areas belonged to the hardest hit by this spring frost.
1.1.3 Main symptoms of wheat field affected by frost
During the two freezing damages in spring, there are obvious differences in the degree of freezing damage in wheat fields due to different topography, geographical location of wheat field, soil type, soil moisture in the field, cultivation management, variety characteristics and plant growth status. There are four main types: â‘ only the leaves are frozen, and some leaves die in the field; â‘¡ the young ears are partially frozen, although the ears can be headed, but the upper or lower spikelets are not strong and become "incomplete ears"; â‘¢ the young ears are affected Freeze-dried and dead, stems and leaves behave normally, part of the stems and tillers form "no-ear stems", the number of ears obviously decreases; %the above.
1.2 Late lodging
1.2.1 Lodging stems
That is, irreversible bending and breaking occur at the internodes of the stem. Wheat stem lodging generally occurs after jointing. After lodging, the leaves overlap, photosynthesis is severely affected, the unblocking tissues in the plant are blocked, the movement of nutrients and water is blocked, the maturity is delayed, the grains are less, the grains are lower, the earlier the lodging is, the heavier the reduction in yield . The physiological reason for the lodging of wheat is that the development of the stem is poor. The stems are stunted, the base internodes are slender, and the stalks are thin, and prone to lodging. The second is poor nutritional status. Too large a group, insufficient light, and excessive nitrogen nutrition will all lead to a lack of carbohydrates, which is not conducive to the filling of stems and lodging. The third is the change of stalks during the filling period. During the filling stage, a large amount of organic matter stored in the stalks is decomposed and transferred to the grains, so that the mechanical strength of the stalks is weakened, which affects the lodging resistance of the plants. Judging from the lodging situation in the late wheat growth period in 2006-2007, the overgrown wheat field has spotted stem lodging from the booting stage, and the range and degree of lofting gradually increased to reach the maximum value at the maturity stage.
1.2.2 Lodging
That is, the lodging that occurs due to loose roots. There are two obvious characteristics of root lodging compared with stem lodging. The first is that the plant is not inclined, and the second is that it occurs at a later time, generally from the filling stage to the mature stage, and it is prone to large-scale lodging, rather than spot lodging. The reason for the occurrence of lodging is mainly due to the windy weather after watering and raining, which loosens the root system of wheat and weakens the bearing capacity. On August 20-22, 2007, there were continuous strong winds and heavy rains. The wind force was 5-6 levels, and the gusts were 7 levels. This caused large areas of wheat roots to fall, and many plots fell to 60% -80% of the area.
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