Studies On Fruiting Response To Carbohydrates Stem Injection And Hormone Treatments Of Newhall Navel Orange Trees

Recently,the citrus industry of our country has been developed rapidly.However,there are still many problems in the process of citrus production,such as lower yield efficiency and fruit quality,which lead to the lack of competitiveness in the international market.Main citrus production area of China located on southern mountains,so the researchers need to deal with more complicated ecological climate and terrain.In addition,citrus,a perennial evergreen fruit crop,its growth regulation mechanism is much more complex and difficult to carry out research than the crops of wheat,rice and apple.In recent years,the stem injection technology has been used in nutrition supplement of fruit trees to fruit quality improvement,plant nutrient deficiency and other fields widely.In this investigation,12-year-old Newhall Navel Orange trees[Citrus sinensis?L.?Osb×Poncirus trifoliate?L.?Raf.]grafted on trifoliate orange[Citrus sinensis?L.?Osb×Poncirus trifoliate?L.?Raf.] root stock were applied as experimental materials to carry out the experiments of stem injection of different kind of sugars and spraying hormone with the aim to the influence on fruit bearing,carbohydrate metabolism and photosynthetic performance.The main results are as follows:1.Influence of stem injection of different sugars and spraying hormone?BA+GA?on fruit bearing.?1?The experiments of stem injection of sucrose,fructose and glucose were carried out 30 days before Full Flower Period?FFP?and during FFP,and spraying hormone?BA+GA?were carried out on 7 days and 21 days after full flower period.The two-year results showed that sucrose stem injection had the best influence on tree fruit bearing by improving the fruit bearing rate?FBR?significantly due to increasing flower drop rate?FDR?and decreasing 1st physiological fruit drop rate?1st PFDR?.However,FDR decreased significantly by fructose stem injection resulting in intense nutrition competition during 1st and 2^nd Physiological Fruit Drop Period?PFDP?,so fructose stem injection had a worse influence on the fruit bearing than the other treatments.Compared with sucrose stem injection,glucose stem injection decreased FDR significantly,and the fruit bearing rate increased significantly,but the difference of fruit bearing number between glucose stem injection treatment and Control cannot achieve to a significant level.In addition,spraying BA+GA also had a better influence on fruit bearing due to lower FDR and 1st PFDR mainly,and the mechanism of fruit bearing regulating was different significantly from sucrose stem injection.?2?The sucrose,glucose,fructose stem injection and spraying BA+GA treatments had a significant influence on fruit quality.The results showed that sucrose stem injection significantly increased fruit color and fruit weight.Moreover,fruit internal quality of sucrose stem injection trees improved much more than other treatments.However,spraying BA+GA treatment decreased the internal fruit quality significantly.2.Influence of different sugars stem injection and spraying hormone?BA+GA?on photosynthetic ability.The effects of sucrose,glucose,and fructose stem injection and spraying BA + GA on leaf chlorophyll pigment content and chlorophyll fluorescence kinetics of Newhall navel orange tree were evaluated.The results showed that sucrose stem injection decreased photosynthetic pigment content and photosynthetic performance of leaves with the incensement time of stem injection under the local experimental conditions.However,fructose and glucose stem injection had no obvious inhibitory effect on the pigment synthesis of leaves,but the photosynthetic parameters slightly decreased.In addition,the leaf pigments increased slightly after BA+GA treatment,but the photosynthetic parameters significantly decreased.3.Influence of different sugars stem injection and spraying BA+GA on carbohydrate metabolism.Sucrose,glucose and fructose stem injection had a significantly different influence on leaf carbohydrate content during the different physiological period of Newhall navel orange tree.The leaf soluble sugar and sucrose content of FFD and 1st PFDP was increased significantly by sucrose stem injection,but the starch content of the two periods was significantly decreased.Whilst,the leaf sucrose content of 2^nd PFDP was significantly decreased.Fructose stem injection significantly increased the soluble sugar,sucrose and starch content in the leaf of FFP.However,with the increment time of stem fructose injection,the soluble sugar content in leaves decreased significantly in the subsequent period.Stem glucose injection significantly increased the starch content in leaves of FFP,1st and 2^nd PFDP.However,the starch content in leaves of 1st and 2^nd PFDP was reduced significantly by spraying BA+GA,and the soluble sugar of 1st and 2^nd PFDP increased gradually.However,the sucrose content was significantly decreased.4.Screening factors in relation to tree productivity for yield prediction modelIn order to screen the critical period and key parameters for monitoring productivity of citrus tree,the key parameters of FFP,1st and 2^nd PFDP were evaluated by Partial Least Squares?PLS?method.The results showed that 2^nd PFDP can be applied as the better monitoring period,and the R2 Y and Q2 values of prediction model achieved to 0.494 and 0.433,respectively.