| Cold stress occurs frequently during different growth stages of wheat, which usually affects the growth, development, and yield formation in wheat. This study was conducted on the Experimental Farm of Jiangsu Provincial Key Lab of Crop Genetics and Physiology, Yangzhou University, from 2012 to 2014. The regulating effects of using remedial fertilizer after low temperature stress on plant growth, yield formation, and physiological characteristics at tillering and jointing stages in spring wheat cultivar Yangmai 16 were studied using an artificial temperature-controlled phytotron system. The regulation measures with the aim of minimizing cold damage were also suggested. This study is of theoretical and practical importance for combating cold stress and stabilizing grain yield in wheat. The main results were as follows:1. The grain yield of Yangmai 16 treated with low temperature stress at tillering stage and jointing stage decreased as the increase in cold tress duration. The number of ear increased by applying remedial fertilizer was the main reason for increasing grain yield at tillering stage. At jointing stage, fertilizer amendment mainly improved grain yield by increasing the grain number per ear, followed by ear number. With increased fertilizer applying amount under the same treatment duration, the growth of wheat plants were better restored and the loss of grain yield was lessened. At tillering stage, considering recovery effect and nitrogen production efficiency, 75 kg/ha urea would be recommended for nitrogen amendment when wheat plants were damaged slightly and the cold index was about 0.2. When the cold index was about 0.36,120 kg/ha urea would be suggested. When the cold index was about 0.50,180 kg/ha urea was recommended for recovering wheat growth after severe cold damage. At jointing stage, when the cold index was about 0.35 after slight cold damage, the amendment of 105 kg/ha urea was recommended. The application of 150 kg/ha urea would be suggested when the cold index was about 0.50. When the cold index was about 0.66, the amendment of 225 kg/ha urea was recommended under severe cold stress.2. Cold injury degree on wheat plants and the cold index were increased with longer duration of low temperature at tillering stage and jointing stage, resulting into lowered plant height. Remedial fertilizer after cold stress mainly promoted the length of the two bottom internodes at tillering stage and the length of the two upper internodes at jointing stage, which recovered ear length and plant height.3. The activities of SOD, POD, CAT, and the content of MDA in leaves of the treatments without nitrogen amendment relief measures increased with the progress of low temperature stress at tillering and jointing stages. On the 10th day after nitrogen amendment to cold-damaged plants, the antioxidant enzymes activities and the content of MDA were significantly decreased with the increase in nitrogen amount. On the 20th day of after applying remedial fertilizer to cold-damaged wheat plants, the activities of these enzymes and the content of MDA decreased and further reduced to the levels of the controlled plants in natural environment on the 30th day after nitrogen amendment.4. The contents of soluble sugar and pro line of the treatment without fertilizer amendment increased with the progress of low temperature stress both at tillering and jointing stages. The contents of soluble and proline of treatment applying remedial fertilizer after cold stress were lower than those of the treatment without fertilizer amendment. The contents of soluble sugar and proline of these treatments gradually declined and reached the levels of the controlled plants in natural environment from the 10th day to 30th day after applying remedial fertilizer.5. The contents of ABA and ZR of the treatment without fertilizer application gradually increased with the duration of treatment time after low temperature stress at tillering and jointing stages. For the treatment with the same duration time, the contents of ABA and ZR decreased with the increased fertilizer applying amount. The contents of ABA and ZR dropped on the 10th day after using urea to recover wheat growth, and this trend continued and reached the levels of the control on the 30th day. The change of GA3 content was opposite to those of ABA and ZR contents in leaves.6. The absorption of nitrogen, phosphorus, potassium, calcium, and molybdenum in treatments after using recovery fertilizer was higher than those of treatments without fertilizer amendment after low temperature stress at tillering and jointing stages. For the treatment with the same duration time, the absorption of these elements increased with increased urea applying amount. At tillering stage, there existed two important nitrogen absorption phases after nitrogen amendment to recover after cold stress, one from the 10th day after nitrogen amendment to jointing stage, and another from anthesis to maturity. For the treatments of nitrogen amendment at jointing stage, the highest nitrogen absorption occurred from anthesis to maturity, followed by the phase from jointing stage to anthesis.7. The atmospheric temperature (shelter temperature) and canopy temperature in the two cropping seasons changed gently in rainy days. The canopy temperature was 0.1-0.2℃ lower than air temperature. On the contrary, the atmospheric temperature and canopy temperature changed greatly in sunny days. The difference between air temperature and canopy temperature varied greatly. Wheat plants were easily damaged due to lower canopy temperature in sunny days. During wintering stage, the canopy temperature was lower than air temperature from 0:00 to 7:00 AM. The difference between them was 1.0-1.8℃ when air temperature was the lowest. The lowest canopy temperature was at 6:00 AM at jointing stage, which was four degree lower than air temperature. The lowest canopy temperature was at 5:00 AM both at booting stage and anthesis stage. Young ears were easily damaged and the anthesis was postponed due to lower canopy temperature. |
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