Comparative proteomics analysis of tea leaves exposed to subzero temperature:Molecular mechanism of freeze injury

Tea freeze injury is one of the most severe agro-meteorological disasters,which leads to sizable losses of tea production in China.The freezing resistant ability of overwintering tea trees becomes weaker and weaker from early-spring to late-spring.If it decreases to critical temperature of-2℃or lower in the stage with one or two leaves,tea trees suffer from freeze injury and the yield or quality of spring tea production could decrease greatly.Although measurements have been taken to prevent such damage,the physiological and biochemical mechanism of how tea(Camellia Sinensis)plant response to freeze injury is still to be elucidated.A comparative proteomics analysis was made on tea leaves at the two-leaf stage.The differential image analysis showed 46 spots with density changes(29 spots increased and 17 spots decreased;p<0.01)in the freeze injury group compared with the control group.Thirty eight differential protein spots(p<0.01)with good resolution and relatively high abundance in MS were subjected to further protein identification.Among them,all 17 up-regulated spots were collected whereas only six of the down-regulated spots were selected.These differentially expressed proteins including heat shock protein 70,oxygen-evolving enhancer protein,adenosine triphosphate synthase,S-adenosylmethionine synthetase and some enzymes involved in carbohydrate metabolism,were shown responsive to freeze injury.The results would greatly increase the comprehension of the molecular mechanism for freeze injury and provide a better decision making for freeze protection and control.

Expert consensus on the prevention, diagnosis and treatment of cold injury in China, 2020

Cold injury refers to local or systemic injury caused by a rapid, massive loss of body heat in a cold environment. The incidence of cold injury is high. However, the current situation regarding the diagnosis and treatment of cold injury in our country is not ideal. To standardize and improve the level of clinical diagnosis and treatment of cold injury in China, it is necessary to make a consensus that is practical and adapted to the conditions in China. We used the latest population-level epidemiological and clinical research data, combined with relevant literature from China and foreign countries. The consensus was developed by a joint committee of multidisciplinary experts. This expert consensus addresses the epidemiology, diagnosis, on-site emergency procedures, in-hospital treatment, and prevention of cold injury.

Evaluation on Climate Suitability in Main Growth Stages of Zhaotong Apple in Recent 60 Years

Based on daily average temperature,precipitation and sunshine hours during 1961-2018 from two meteorological stations of Zhaoyang District and Ludian County at Zhaolubazi,Zhaotong City,Yunnan Province,using the freezing injury index at flowering stage(Ha),climatic suitability index during expansion period(Pa),climatic suitability index during coloring period(Dy)and climatic suitability index during fruit growing period(Si),etc.,the climatic suitability of Zhaotong apple during the main growth stages was evaluated.The results showed that the annual average temperature was 11.8-12.3℃at Zhaolu Bazi in recent 60 years,and the climate was the most suitable for Fuji apple planting both in the south and north;the average annual precipitation was 674.8-852.6 mm,and the climate was suitable in the north and sub-suitable in the south;the annual average sunshine hours was between 1845.4 and 1851.1 h,and the climate was sub-suitable in both areas.The Ha was between 0.42-0.50,serious in the north and moderate in the south;the Pa was between 0.92 and 1.02,and both the south and the north were suitable areas;the Dy was between 0.95 and 1.00,and the climate in the south was suitable,while it was sub-suitable in the north;the Si was between 1.38 and 1.59,and the climate was suitable in the south and sub-suitable in the north.There was a 4-year cycle in the interannual variation of Ha,Pa,Dy and Si.After the 1980s,the Ha decreased by 0.56-0.59,the Pa,Dy and Si respectively increased by 0.10-0.16,0.14-0.15 and 0.78-0.84 with the temperature rise,and the changes of these four indexes were all favorable for Fuji apple's fruits growth.It can be seen that under the background of the global warming,the climatic conditions in Zhaolu Bazi are becoming more and more favorable for popularizing the planting of Fuji apple.

Assessing and characterizing oilseed rape freezing injury based on MODIS and MERIS data

The oilseed rape growing in the lower reaches of Yangtze River in China belongs to winter varieties and suffers the risk of freezing injury.In this research,a typical freezing injury event occurred in Anhui Province was taken as a case study,the freezing damage degree of oilseed rape was assessed,and its development characteristics based on the vegetation metrics derived from MODIS and MERIS data were investigated.The oilseed rape was mapped according to the decline of greenness from bud stage to full-bloom period,with the phenological phases identified adopting time-series analyses.NDVI was more sensitive to freezing injury compared with other commonly used vegetation indices(VIs)calculated using MODIS bands,e.g.,EVI,GNDVI and SAVI.The freezing damage degree employing the difference between post-freeze growth and the baseline level in adjacent damage-free growing seasons was determined.The remote sensing-derived damage levels were supported by their correlation with the cold accumulated temperatures at the county level.The performance of several remote sensing indicators of plant biophysical and biochemical parameters was also investigated,i.e.,the photosynthetic rate,canopy water status,canopy chlorophyll content,leaf area index(LAI)and the red edge position(REP),in response to the advance of the freezing damage.It was found that the photosynthetic rate indicator—Photochemical Reflectance Index(PRI)responded strongly to freezing stress.Freezing injury caused canopy water loss,which could be detected though the magnitude was not very large.MERIS-LAI showed a slow and lagging response to low temperature and restored rapidly in the recovery phase;additionally,REP and the indicator of canopy chlorophyll content—MERIS Terrestrial Chlorophyll Index(MTCI),did not appear to be influenced by freezing injury.It was concluded that the physiological functions,canopy structure,and organic content metrics showed a descending order of vulnerabilities to freezing injury.

Tea leaf’s microstructure and ultrastructure response to low temperature in indicating critical damage temperature

To find out the critical damage temperature of tea leaf,a new method of subzero treatment was provided by fitting the air temperature data from six heavy frost events.Furthermore,the study explored the characteristics of Fuding Dabai tea plant response to low temperature stress of 2,0,
2,
4,
8,
10 and
15
C by observing the microstructure and ultrastructure changes of the leaves.All samples were collected in an ambient temperature of 8.6
C which served as control.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were used to observe the microstructure and ultrastructure of stomata and mesophyll.SEM observation results indicated that stomata of tea leaves have an obvious low temperature stress when the temperature was lower than
2
C.The extent of opening of the stomata increased and enhanced guard cell protection of tea leaves against cold injury.However,dehydration,shrinkage and deformation of cells occurred as the temperature decreased from
2
C to
15
C.TEM observations showed that the cell nucleus,cell walls,chloroplasts and mitochondria all had normal structure at a temperature of 8.6
C where the membrane and granum lamella were clearly visible.As the temperature decreased to
2
C,the membrane system of tea leaf was the first to be damaged and the cell walls became fuzzy.Therefore,the leaf microstructure and ultrastructure showed obvious changes at
2
C,which might define the critical damage temperature for freeze damage of Fuding Dabai tea.Control strategy based this critical damage temperature is useful for wind machine frost protection in tea fields within the Yangtze River region.