| In recent years,with the increasing greenhouse effect,the intensity and frequency of cold fall in spring are more and more serious and frequent.The serious year of disaster has led to more than 50% reduction of wheat yield.In order to explore the mechanism of the effect of cold fall on the accumulation,distribution and yield of dry matter in wheat,Yannong 19,a strong resistance to cold in the spring,and Xinmai 26,a weak resistance to the cold,were selected as the test varieties.The artificial climate box was used to simulate the low temperature stress treatment at 2℃,0℃ and-2℃ for 4 hours in the anther interval period from 1:00 to 5:00 in the morning,in order to clarify how the late spring cold affects the accumulation of dry matter,reduces the transport and distribution of photosynthates,and finally leads to the decrease of seed setting rate and grain yield.It provides theoretical basis for wheat disaster prevention,disaster reduction,production and quality improvement.The main results are as follows:1.The dry matter accumulation in flowering and mature stage was significantly reduced by cold stress in the anther interval.Compared with the control at 15 ℃,the dry matter accumulation in flowering and mature stage decreased with the increasing of low temperature stress(2℃→-2℃).The T1,T2 and T3 treatment of Yannong 19 were 33.4%,46.2% and54.7% lower than that of the control,while Xinmai 26 decreased by 50.1%,59.3% and 72.4%respectively.The dry matter accumulation of Xinmai 26,a weak cold resistant variety,decreased more than that of Yannong 19.2.The low temperature stress significantly reduced the dry matter transport before anther,and the varieties with weak resistance to cold in spring decreased significantly.Among them,the T3 treatment of Yannong19 and Xinmai26 decreased 87.9% and 98.3% respectively compared with CK.The transfer efficiency of dry matter before anther,contribution rate of dry matter to grain and assimilation of dry matter after anther decreased with the decrease of temperature.But the contribution rate of dry matter to grain increased with the decrease of temperature,and the T1,T2 and T3 treatments of Yannong 19 increased by 5.0%,6.5% and10.8% respectively,while T1,T2 and T3 treatment of Xinmai 26 increased by 2.9%,6.3% and8.0% respectively.3.The dry matter accumulation of spike,stem sheath and leaf in flowering stage was significantly reduced by cold stress in the interval of anthesis,and the distribution ratio of stem sheath and leaf was increased.At the same time,the dry matter accumulation of wheat grain,spike axis + chaff,stem sheath + leaf was significantly reduced,and the proportion of dry matter distribution in ear was decreased,but the distribution ratio of stem sheath + leaf increased with the decrease of temperature,and the increase of cold resistant varieties was greater.Among them,the T1,T2 and T3 treatment of Yannong19 increased 58.2%,87.7% and94.7% respectively compared with CK,and T1,T2 and T3 treatment of Xinmai 26 increased81.3%,106.5% and 117.4% respectively.4.The low temperature stress in the anther interval decreased the grain yield significantly with the decrease of temperature,and the varieties with weak resistance to cold in spring decreased more.The effect of low temperature stress on wheat yield was grain number per spike> grain weight >spike number.The number of grains per spike and the weight of single spike were significantly reduced by low temperature stress in the anther interval,among which the number of spike grains in T1,T2 and T3 treatments of Yannong 19 decreased by 52.74%,85.08% and 98.04% respectively,while that of Xinmai 26 was 95.77%,97.91% and 98.30%respectively.The grain weight of T1,T2 and T3 of Yannong 19 was reduced by 7.12%,8.0%and 8.37% respectively,while that of Xinmai 26 was 9.96%,15.24% and 15.28% respectively;The single spike weight of Yannong 19 decreased 56.06%,86.36% and 98.10%,while Xinmai26 decreased 96.15%,98.07% and 98.46% respectively. |
