Effect of low temperature chilling injury on Rice and its Preventive measures

Rice chilling injury means that rice suffers from the influence of low temperature below the lowest critical temperature, which leads to the abnormal growth and development of rice and the reduction of rice yield. According to the different period of injury, it can be divided into delayed chilling injury, obstacle chilling injury and mixed chilling injury.

I. types and characteristics of chilling injury in rice

The main results are as follows: 1. During the vegetative growth period, sometimes including the reproductive growth period, the delayed chilling injury rice suffered from the harm of lower temperature for a long time, which weakened the physiological activity of the rice plant, delayed the growth and development, delayed the heading and flowering, and resulted in a significant reduction in yield due to insufficient grain filling and maturity. In the early stage, the temperature was normal and the heading was delayed, while in the later stage, due to abnormal low temperature, the flowering, pollination and filling maturity was delayed. Rice suffered delayed chilling injury, the blighted grain increased, the 1000-grain weight decreased, the rice quality was poor, and the yield decreased seriously.

2. During the reproductive period, obstacle chilling-injured rice suffered a relatively strong low temperature for a short time, which destroyed the physiological mechanism of the floral organ, resulting in sterility of spikelets, a large number of empty shells, and a serious reduction in yield. According to the period of suffering from low temperature, it can be divided into chilling injury at booting stage and chilling injury at heading and flowering stage. when the temperature at booting stage is lower than 17 ℃ 5-6 days, it will cause a large number of spikelets to degenerate or unable to form normal pollen grains and eggs, resulting in a large number of empty shells; when the temperature at heading and flowering stage is lower than 20 ℃, a large number of glumes will not open, anthers will not split, pollen or pollen germination rate will decrease greatly, so sterility will result in reduced yield.

3. in the same year, delayed chilling injury and obstacle chilling injury occurred at the same time. In the early growth stage, low temperature delayed the growth and development of rhizome and leaf tillers, delayed panicle differentiation, delayed heading, and affected the yield. Low temperature during booting, heading and flowering will cause spikelet sterility or partial sterility, delay ripening and produce a large number of empty chaff grains.

2. effects of low temperature and chilling injury on nutritional physiology of rice

1. Low temperature weakens photosynthesis, which is mainly due to the denaturation of protein in chloroplast and the decrease of enzyme activity, thus reducing the photosynthetic intensity of plants.

2. Low temperature reduces the intensity of respiration, and respiration is an indispensable condition for maintaining plant growth and development. During the growth and development of rice, when the temperature decreases by 10 ℃ from the optimum temperature, the respiratory intensity will be reduced by 1.6 to 2.0 times.

3. The effect of low temperature on the absorption of mineral nutrients, the energy absorbed by roots comes from respiration, and low temperature weakens the respiration of roots, which reduces the energy needed to supply plants to absorb mineral nutrients, resulting in the weakening of plant absorption of nutrients and the destruction of plant nutrient balance.

4. The effect of low temperature on nutrient transport, low temperature not only reduces the photosynthetic intensity of rice plants, affects the absorption of mineral nutrients by roots, but also hinders the transport of photosynthates and nutrient elements to the growth organs, and reduces the transport speed.

Measures against low temperature and cold injury

The main results are as follows: 1. Establish and improve the breeding system of improved varieties, purify the existing varieties, maintain and enhance the species and resistance of the original varieties, introduce and cultivate early-maturing and high-quality varieties with strong cold resistance.

2. Soil preparation in autumn, soil preparation in autumn and making bed in autumn. After the beginning of spring, the temperature was accumulated, seedlings were raised early, and the ground temperature was raised by plastic film in early spring. When the air temperature passed steadily through 5: 6 ℃, the seedlings began to sow, and when the air temperature steadily passed 13 ℃, the seedlings began to transplant.

3. Fertilization technology to prevent chilling injury. (1) to control the application of nitrogen fertilizer, in the case of cold injury years, the total amount of nitrogen fertilizer should be reduced by 2030%, the remaining nitrogen fertilizer should be used as base fertilizer and tiller fertilizer, and 20% should be used as panicle fertilizer 10-20 days before heading. (2) by increasing the application of phosphorus fertilizer, phosphorus can increase the content of soluble sugar in rice, thus improve the cold resistance of rice, and promote early ripening. All the amount used as base fertilizer can be applied to the soil layer with dense roots at one time. (3) combined with potassium fertilizer and trace elements, potassium can promote the metabolic synthesis of carbohydrates and improve the stress resistance of crops. The remaining 30% were applied as topdressing in the later stage. At the same time, some trace elements were properly mixed to improve the quality of rice.

4. Raise the water temperature and ground temperature. Setting up a tanning pool, prolonging the waterway, covering the canal with plastic film, widening the mat height of the water inlet, boiling water to increase the temperature into the field, and adopting backwater irrigation can increase the field water temperature and ground temperature during the day. Deep-water irrigation is carried out in the sensitive period of obstacle cold injury, with a water depth of 17cm to 20cm.