Studies On The Physiology And Influence Factors Of Walnut Fruit Sunburn

Walnut is an important nut and woody oil trees, walnut fruit sunburn waswidespread in recent years, the walnut fruit sunburn rate was10%to12%in hightemperature years in Xingtai of Hebei, which caused significant loss of production. Inorder to reduce the loss of walnut fruit sunburn, in Hebei Lvling Fruit Industry Co.LTD,Effects of fruit sunburn influence factors, prevention methods and the effects of sunburnon antioxidant enzyme activities in green husks of sunburn fruits and kernel quality ofprecocious walnut ’Lvling’,’Luguo1’,’Shangsong6’ which planted in2002were studied.The main results were as follows:1. The fruit sunburn rates of ’Lvling’,’Shangsong6’,’Luguo1’ were12.76%,3.60%,2.23%; the sunburn disease indexes were6.77,2.36,1.35. The fruit sunburn rate anddisease index of ’Lvling’ were significant higher than ’Shangsong6’ and ’Luguo1’.2. The highest fruit surface temperatures on different exposures of canopy of the threecultivars at10:00,11:00were the east; and those at12:00to16:00were the west. Therehad no significant differences of ’Lvling’ fruit surface temperature of east,south,west andnorth at10:00,11:00,12:00,13:00; there had significant differences of those at14:00,15:00,16:00. There had no significant differences of ’Shangsong6’ fruit surfacetemperature of east,south,west and north at10:00,11:00,12:00,13:00; there hadsignificant differences of those at14:00,15:00,16:00. There had no significant differencesof ’Luguo1’ fruit surface temperature of east,south,west and north at10:00,11:00,12:00;there had significant differences of those at13:00,14:00,15:00,16:00.3. The highest fruit surface light intensities on different exposures of canopy of thethree cultivars at10:00,11:00were the east; and those at12:00to16:00were the west.There had very significant differences of ’Lvling’ fruit surface light intensities of east,south, west and north at10:00to16:00. There had significant differences of ’Shangsong6’fruit surface light intensities of east,south,west and north at10:00; there had verysignificant differences of those at11:00to16:00. There had very significant differencesof ’Luguo1’ fruit surface temperature of east, south, west and north at10:00,11:00,13:00,14:00,15:00; there had significant differences of those at13:00,16:00. 4. There had no significant differences of the three cultivars fruit surface relativehumidities on different exposures of canopy of the east, south, west and north at10:00,11:00,12:00,14:00,15:00and16:00. The ’Lvling’ fruit surface relative humidity of theeast at13:00was significant higher than that of the west; the ’Shangsong6’ fruit surfacerelative humidities of the east and the north were significant higher than that of the west;the ’Luguo1’ fruit surface relative humidity of the north was significant higher than thatof the west.5. The fruit sunburn rates and disease indexes among four directions of the threecultivars were as follows: west> south> east> north; and there had very significantdifferences among four directions.6. When the light intensity was106200Lx, the fruit surface temperature increased by7.20℃thanthat shaded by cartons.7. The correlation coefficients of the fruit surface temperature and the fruit sunburndisease index and sunburn rate of ’Shangsong6’ were0.844,0.879, which reached verysignificant correlation; the correlation coefficients of fruit surface temperature and thefruit sunburn disease index and sunburn rate of ’Lvling’ were0.772,0.773, which reachedsignificant correlation.8. The fruit sunburn critical temperatures of ’Lvling’,’Luguo1’,’Shangsong6’ were (43.3±0.5)℃,(45.8±0.5)℃,(45.5±0.5)℃; thecritical light intensities were (83900±100)Lx,(96600±100)Lx,(90500±100)Lx.9. The SOD, CAT activities and MDA content in green husks of different sunburnlevels increased at first and then decreased, the SOD, CAT activities increased within acertain range of stress sunburn, POD activity increased by the sunburn degree aggravated,the O2-production rate, relative conductivities increased by sunburn levels, and there hadsignificant differences between the different levels.10. The kernel rate of sunburn walnut in Ⅳ level of ’Lvling’ was very significant lowerthan those of the0level (non-sunburn),Ⅰlevel, Ⅱ level, Ⅲ level. The kernel rates ofsunburn walnut in Ⅲ and Ⅳ levels of ‘Shangsong6’ were very significant lower thanthat of the0level (non-sunburn). The kernel rate of sunburn walnut in Ⅳ level of’Luguo1’ was very significant lower than those of the0level (non-sunburn),Ⅰlevel, Ⅱlevel. The kernel total protein contents of sunburn walnut in Ⅱ level, Ⅲ level,Ⅳ levelof ’Lvling’ were very significant lower than that of the0level. The kernel total proteincontents of sunburn walnut in Ⅰlevel,Ⅱ level, Ⅲ level,Ⅳ level of ‘Shangsong6’were very significant lower than that of the0level. The kernel total protein contents ofsunburn walnut in Ⅲ level, Ⅳ level of ’Luguo1’ were significant lower than that of the0level,Ⅰlevel. The kernel soluble protein content of sunburn walnut in Ⅲ level of’Lvling’ was very significant higher than that of the0level. The kernel soluble proteincontents of sunburn walnut in Ⅰlevel,Ⅱ level, Ⅲ level,Ⅳ level of ‘Shangsong6’ were very significant higher than that of the0level. The kernel soluble protein content ofsunburn walnut inⅠlevel of ’Luguo1’ was significant higher than those of the0level, Ⅲlevel,Ⅳ level. Among the three cultivars, the kernel fat content only in Ⅳsunburn levelof ’Lvling’ was very significant lower than that of non-sunburn fruits, low to5.83%. Thekernel color of the Ⅳ sunburn level in the sunburn position of the three cultivars turneddark brown, and lost commodity value.11. The fruit sunburn rates of sprayed water (control),0.2%KH2PO4,0.1%Vc,0.2%Vc,0.3%Vc,(1%lime+0.1%saline),3%kaolin,6%kaolin,9%kaolin on fruit were10.58%,7.04%,10.32%,10.26%,7.57%,9.23%,7.17%,6.57%,6.52%respectively, thefruit sunburn rates of sprayed0.2%KH2PO4,0.3%Vc,3%kaolin,6%kaolin, and9%kaolin were very significant lower than that of control; the fruit sunburn disease indexeswere6.34%,4.61%,6.31%,6.18%,4.58%,5.42%,4.43%,3.86%,3.72%respectively,the fruit sunburn disease indexes of sprayed0.2%KH2PO4,0.3%Vc,3%kaolin,6%kaolin,9%kaolin were very significant lower than those of control and sprayed0.1%Vcsolution.12. The horizontal diameters of sprayed KH2PO4was significant higher than those ofsprayed0.1%Vc and9%kaolin; the average three diameters of control, sprayed0.2%KH2PO4,0.3%Vc,(1%lime+0.1%saline),3%kaolin,6%kaolin were very significanthigher than those of sprayed0.1%Vc and9%kaolin; there were no significant effects ofdifferent spraying materials on nut vertical diameter, side diameter, nut weight, kernelpercent.13. The kernel soluble protein contensts of sprayed0.2%KH2PO4and0.3%Vc weresignificant higher than that of sprayed3%kaolin; the kernel total protein content ofsprayed0.2%Vc was significant higher than those of sprayed9%kaolin and control;there were no significant effects of different spraying materials on kernel fat contents.