| The field experiments were conducted in farm of Yangzhou University,Jiangsu Province at Yangzhou in 2016?2017,the experiments set potted plants.Four rice varieties were used as tested materials,including Nanjing 9108,Huaidao 14,Yangliangyou 013 and Yangliangyou NO 6.The low temperature treatment was carried out at the booting stage(-5?-2cm of the leaf occipital distance).The test set three temperature,13??15?and 17? constant temperature treatment,each temperature was set CK(control),3?5?7?9 days treatment,artificial climate chamber internal relative humidity and light intensity during the simulation test The external natural conditions are set.In the daytime(6:00-18:00),a set of light supplementing lamps was set.The humidity was set at about 70%,and the intensity of illumination was about 15Klux.Turn off the light at night(18:00-6:00).The humidity is set at about 80%.Rice under natural growth conditions was used as control.In this experiment,the effects of low temperature and duration of the booting stage on rice yield,grain filling,quality and physiological characteristics were studied in order to provide a scientific basis for the prevention and evaluation of rice cold damage and high yield and high quality production in Jiangsu.The main results were as follows:1.Different low-temperature injury at booting stage had significant effects on rice growth and yield formation,and there were some differences among varieties.With the decrease of temperature and prolongation of processing time,plant height,panicle length and internode length decreased gradually,resulting in a decrease in dry matter weight at maturity.At the same time,the grain plumpness decreased and the empty shell rate increased.The reduction of grain yield,seed setting rate and 1000 grain weight were the main reasons for the significant decrease in grain yield,and the decrease of seed setting rate was the largest among yield components.The effect of low temperature injury on rice yield was different between varieties.The yield and its constituent factors of Nanjing 9108 at 17 ? and over three days were significantly different from the control,while the other varieties were significantly different from the control under the different days of three temperatures,and the lower range of Yangliangyou 013 was greater than that of the other varieties.In addition,indica rice varieties were more affected by low temperature damage than japonica rice varieties,among which,Nanjing9108 showed strong cold tolerance,Yangliangyou 013 could not endure low temperature above five days at 13? and could not be in time for heading filling.2.The photosynthetic characteristics and antioxidant enzyme activities of four rice varieties showed different tolerance under different low temperature and duration,and there were differences among varieties.The chlorophyll content of rice leaves showed a downward trend,and the chlorophyll content decreased with the decrease of temperature and the prolongation of processing time;The net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular C02(Ci)concentration and transpiration rate(Tr)of leaves decreased significantly,there were differences among the varieties.That is,with the prolongation of the processing time,the trend of first descending,then descending or then descending first,and the net photosynthetic rate of the cold sensitive varieties is much lower than that of the cold resistant varieties.It shows that the cold resistance of the four varieties is different,Low temperature at booting stage resulted in increased activity of SOD,POD and CAT in flag leaves.With the prolongation of low temperature,the activity decreased,That is at the booting stage,the activity of SOD,POD and CAT in flag leaves increased first and then decreased;The content of MDA increased with the decrease of temperature and the prolongation of treatment time,In addition,the ability of anti oxidant oxidase to scavenge reactive oxygen species of Nanjing 9108 was stronger,which made the membrane lipid peroxidation weakened,and the final MDA content was lower than that of low temperature resistant varieties.3.The effect of different low temperature injury on the rice quality of four rice varieties at booting stage reduced the processing quality of rice varieties and reduced the brown rice rate,the rate of fine rice and the whole precision rice rate in different degrees,among which the drop of the whole precision rice rate was the greatest;The effects of appearance and nutritional quality on grain length,grain width,chalky grain rate and chalkiness were reduced;The amylose content and protein content of grains were decreased,the results of nutritional quality are inconsistent with previous studies,the relationship between the temperature at booting stage and amylose and protein content is.still uncertain,this may be related to the complexity of amylose and protein content.The decrease of starch content,the increase of chalkiness and the decrease of 1000 grain weight greatly reduced the quality of rice,thus it can be seen that low temperature stress has a serious adverse effect on the quality of rice.The effect of low temperature and cold injury on the RVA spectrum of rice starch at booting stage showed that the lower the temperature of the booting stage and the longer the low temperature,the peak viscosity,the viscosity of the hot pulp,the final viscosity and the disintegration value gradually decreased;The reduction value gradually increased,the peak viscosity time gradually delayed,and the change of the initial gelatinization temperature showed the opposite trend among the varieties,that is,the gelatinization temperature of the japonica rice varieties decreased gradually at low temperature,and the gelatinization temperature of the indica rice varieties increased gradually at low temperature.Generally speaking,the highest viscosity and disintegration value of starch are large,and the reduction value is small.The taste of rice is better.It can be seen that low temperature stress at booting stage makes rice taste quality worse. |
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