| Sweet Cherry（Prunus avium L.）,also called Great Cherry,USA Cherry,Cherry or European Sweet Cherry,fills the lack of fresh fruit in the late spring and early summer because of its earlier fruit maturing,therefore it is known as "First Fruit in the Early Spring".Ripe sweet cherry features gorgeous color and delicious taste,rich nutrition and higher health-care value,as a consequence it is deeply loved by people.Selenium（Se）is one of the necessary trace elements to human body,and Se content in sweet cherry fruit is less.Exogenous application of Se can increase the Se content in sweet cherry fruit and improve its nutrition and commodity values.On the other hand,the period of harvesting sweet cherry is from May to July,when is the high temperature season.With its thin skin,soft pulp,rich juice and worse storage,therefore it has important significance to explore simple and effective fresh-keeping technology for extending its sales period and adapting to the long-distancetransportation.1-methylcyclopropene（1-MCP）as ethylene inhibitor has good effects on storage and fresh-keeping to a variety of fruit and vegetables.Its effects on sweet cherry,especially the fresh-keeping of selenium-rich fruit remains to be further validation.In this paper,‘Tieton’,a variety of sweet cherries,serves as the test materials and has got the following processes: 1.After blossom dropping,the sweet cherry foliage is sprayed by sodium selenite（Na2Se O3）liquor and the concentrations are respectively 0,5,10,20 and 40mg·L-1,then repeating spraying after one week.The changes of the main physiological and biochemical indices,fruit quality and heavy metal content in foliage and fruit in the sweet cherry are measured after applying different concentrations of exogenous selenium.2.The harvested fruit applied by 0 and 40 mg·L-1 Na2SeO3 as the test materials are processed by 1-MCP of the 0 and 1μL·L-1 concentration,namely the test includes the following four treatments:1(control,0mg·L-1Na2SeO3+0μL·L-11-MCP),2(40mg·L-1Na2SeO3+0μL·L-11-MCP),3(0mg·L-1Na2SeO3+1.0μL·L-11-MCP),4(40mg·L-1Na2SeO3+1.0μL·L-11-MCP).Thespecific method is to set the test fruit into 1-MCP under the normal temperature and fumigate 24 hours,then store them in cold storage of 1 ℃.During the determination,the sweet cherry fruit under different processes are tested the main quality index,rot and weightless conditions.The main results are as follows:1.Application of different concentration Na2SeO3 on the foliage significantly increases the Se content in sweet cherry fruit and foliage,and it can be seen that the Se content in fruit and foliage gets a progressive increase with the increase of Se concentration.The correlation coefficient of Se content in fruit and foliage is 0.904 * * and reaches extremely significant positive correlation.It shows that the increase of Se content in fruit mainly comes from the exogenous Se on foliage.The foliage Se content are respectively control 3.06,7.01,8.61 and 15.06 times after application of 5,10,20 and 40 mg·L-1 concentration Na2SeO3,significantly higher than control.Se content in fruit are respectively control 1.09,5.74,8.76 and 9.36 times,reaching 1.8812,9.9196,15.1357 and 16.1717μg·kg-1,of which Se content in fruit aresignificantly higher than control while application of 10,20 and 40mg·L-1 Selenium concentration and reach the Se-rich food standards.2.The content of heavy metal cadmium and lead in foliage and fruit all decrease in different degrees by application of different concentration Se on the sweet cherry foliage,of which the cadmium（Cd）content in fruit drops 36.24% comparing with control while the Se concentration is 5 mg·L-1,and the difference reaches significant level.The percentage of lead content in fruit drops 90.09%,86.78% and 57.13% comparing with control while the concentration are 5,10 and 20mg·L-1 and the difference reaches significant level.Meanwhile with application of Se,the mercury content in foliage and fruit both drop into undetected level.With analyzing the correlation between Se and Cd,and Se and lead in foliage and fruit,it is showed that there is no significant correlation,and the decrease of heavy metal Cd,lead and mercury in the foliage and fruit is not linear to the increase of Se concentration on foliage,after applying selenium on foliage.3.The SOD activity are respectively 131.5367,100.8333,140.9000 and 112.4933μ·g-1,which are 1.65,1.26,1.76,1.26 timesthat of control,by application of Se whose concentration are 5,10,20 and 40 mg·L-1.The decrease percentages of MDA content are respectively less 9.93%,12.36%,19.03% and 8.74% than control.Pro content are respectively 33.1700,37.2033,28.4833 and 37.1400μ·g-1.Comparing with control,the reduces are 24.38,20.35,29.07,20.35μ·g-1,whose differences reach significant level.SOD activity in fruist are respectively more 164.9900,79.9433,103.8167 and 46.1600μ·g-1 and 3.54,2.14,2.60,1.71 times that of control.MDA content are respectively less 38.91%,21.82%,18.29% and 38.91% than control.Pro content are respectively less 8.6653,5.7413,5.2220 and 5.7413μ·g-1 than control.The above results show that application of Se on foliage can significantly increase the SOD enzyme activity in sweet cherry foliage and fruit,with decreasing the activity of MDA and reducing the accumulation of Pro.4.When the Se concentration Na2SeO3 on foliage are10,20 and 40mg·L-1,CO2 concentration in blades intercellular of sweet cherry has a little decrease.But low concentration Na2SeO3,that is 5mg·L-1,less impacts on them.Photosynthesis of sweet cherry foliage changes with the environment,such as temperature in the daylight,light intensity and air humidity.Se application has no apparent influence on the discretion of the net photosynthetic rate and diurnal variation trend.At the same time,stomatal conductance and variation of transpiration rate of sweet cherry foliage also have no obvious change after application of Se on foliage.5.Application of Se on foliage can effectively improve the quality of sweet cherry fruit.The weight of single sweet cherry fruit averagely increase after application of different concentration Se on foliage,the number have not reached significant level comparing with control7.4112 g.Fruit firmness also improve in varying degrees,with the fruit firmness of 5mg·L-1 process fruit is 6.64kg·cm-2,significantly higher than control5.51kg·cm-2.Vc in the sweet cherry fruit increase after application of Se,which Vc after application of 5,10 and 20mg·L-1 are respectively 15.73,12.82 and 12.67mg·100g-1,significantly higher than control.And soluble solids content does not change obviously.Compared with control,the titratable acid content in fruit of application of Se reduces in some extent.But only when Se concentration is 5mg·L-1,the content can reach significant level.And the fruit sugar acid ratio increase,which sugar acid ratio by 5,10 and 20mg·L-1application are respectively 35.11,31.11 and 32.28,significantly higher than control 26.47.6.During the entire storage,fruit rot rate is evidently lower than control,which is an obvious difference,application of 40mg·L-1Na2SeO3+0μL·L-11-MCP,0mg·L-1Na2SeO3+1.0μL·L-11-MCP and 40mg·L-1Na2SeO3+1.0μL·L-11-MCP.And 1-MCP can get a better real effect on Se-rich fruit.Comparing the treatment of 40mg·L-1Na2SeO3+0μL·L-11-MCP with the application of 40mg·L-1Na2SeO3+1.0μL·L-11-MCP,there is no obvious difference on the effect of weight loss of sweet cherry fruit.In the whole storage,the appilcation of 0mg·L-1Na2SeO3+1.0μL·L-11-MCP is superior to other three applications of the control of fruit weight loss.Vc contents in sweet cherry fruit,no matter control or the other three applications,get a reduce in varying degrees.From the whole storage,1-MCP application has little influence on restraining Vc reduce of non-Se fruit and Se-rich fruit.1-MCP application or not has the basically same downtrend on acid,whether to the non-Se application or the Se-rich fruit.1-MCP has no obvious inhibitory effect on the titratable acid reduce.The soluble solids content in sweet cherry fruit presents a trend of first increase then decrease with the extension of storage time.On the tenth storage day,soluble solids content increased significantly because of the after-ripeness of fruit.The soluble solids content in the non-1-MCP application fruit both smoothly increase in early period and decrease in middle period.But the soluble solids content in the 1-MCP treatment fruit both have larger growths in early increase stage and decline stage.It shows that the application aggravate rather than inhibit the respiration of non-respiration climacteric sweet cherry fruit. |
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