Study On The Mechanism Of The Effect Of Nighttime Warming On The Growth And Photosynthetic Characteristics Of Young Spikes In Wheat

Global warming is one of the main trends in global climate change.In recent years,the average surface temperature in China has also increased by 1.1°C,which is higher than the global average warming range during the same period.It is expected to increase by another 1.2°C-2.0°C by 2050.This study used spring wheat varieties Ningmai 13,Yangmai 18,Sumai 188,and semi winter wheat varieties Annong 0711,Jimai 22,and Yannong 19 as test materials.From 2021 to 2022,six wheat varieties were subjected to passive warming treatment:non warming as control（CK）,tillering to jointing stage(W_T-J),jointing to booting stage(W_J-B),and booting to flowering stage(W_B-A)at night.（Average nighttime temperature increase of 1.048°C,1.657°C,and 1.143°C）.The main research conclusions are as follows:（1）The nighttime warming treatment from tillering to jointing stage and from jointing to booting stage achieves high yield by increasing the thousand grain weight and number of grains per spike of wheat.Compared with the control,the nighttime warming treatment from tillering to jointing increased yield by 4.24%（Ningmai 13）,4.75%（Yangmai 18）,4.84%（Sumai 188）,5.44%（Annong 0711）,6.08%（Jimai 22）,and 5.67%（Yannong 19）.From the perspective of spike characteristics,the nighttime warming treatment from tillering to jointing and jointing to booting increased the spike length of wheat,increased the total number of spikelets and fertile spikelets,and reduced the number of sterile spikelets in wheat.Nighttime warming can promote the accumulation of dry matter in wheat from the jointing stage to the flowering stage.The yield of spring varieties and semi winter varieties reflects different stages of nocturnal warming,with semi winter varieties experiencing a significant increase in yield after nocturnal warming before flowering.（2）The nighttime warming treatment from the tillering stage to the jointing stage accelerated the development process of wheat young spikes,and also extended the duration of grain filling.The nighttime warming treatment from tillering to jointing stage and from jointing to booting stage increased the seed length and width of wheat.Nighttime warming reduces the rate of small flower degeneration and fertile small flower abortion,increases the number of small flower differentiation,reduces the number of small flower degeneration and fertile small flower abortion,and is conducive to yield formation.（3）The nighttime warming treatment from tillering to jointing stage and jointing to booting stage improved the photosynthetic capacity of wheat,especially the photosynthetic respiration at night,thereby stimulating the photosynthetic production capacity during the day.The nighttime warming treatment increased the chlorophyll content,photosynthetic parameters,light response curve,fluorescence parameters,etc.of wheat flag leaves,thereby improving the photosynthetic capacity of wheat.The nighttime warming treatment from tillering to jointing stage and from jointing to booting stage makes the stomatal distribution of wheat flag leaves more dense and compact,increases the number of stomata,accelerates CO₂absorption,increases carbohydrate accumulation,and thus improves wheat yield.