Effect Of Silicon On Growth And Development And Absorption Of Nitrogen In Apple Trees

Nitrogen is one of the macronutrients, which the fruit tress growth and development areneeded. Nitrogen fertilizer has been highly valued, especially in the higher lever of intensiveorchards. But the application of nitrogen fertilizer incorrectly can cause adverse consequencesof the decline in fruit quality and tree flourishing （Peng Futian,2002）. In2007, nitrogenfertilizer in China reached22.972million tons （pure, the same below, not included in thefertilizer nitrogen）, which is2.8times in1980, is the world’s first nitrogen fertilizerconsuming country （the People’s Republic of China Ministry of Agriculture,2008）. In recentyears, farmers fertilization survey results show that the orchard average nitrogen applicationrate of more than300kg N ha^-2, resulting in the apple orchard ecosystem nitrogen surplus,and adverse impact on the ecological environment. Silicon has been recognized as one of theuseful elements of the plant, can reduce a variety of biological stress such as pest and diseasestress, can reduce a variety of abiotic stresses including salinity, heavy metal ion toxicity anddrought. The silicon on the relationship between the nitrogen and other mineral elements inrice and other monocots have been reported （Lu Fuyong et al,2005; Zheng Pearl et al,2011）.Malus hupehensis and fifteen-year-old Fuji/Malus robusta Rehd trees were used to studythe effects of silicon on fruit quality and¹⁵N-nitrate calcium and¹⁵N-urea absorption、utilization and allocation by¹⁵N trace technique. The main results were as follows:1、With the fertilization increased, the fruit weight, the soluble solid content and the fruitfirmness was significantly improved, and were respectively higher than the control22.7%、5.4%and17.2%. The NDFF in various organs of treatment2were higher than the control, ofwhich the most significant in the fruit. Regardless of control or treatment, the fruit¹⁵Ndistribution rate was higher than the other organs. The treatment2was higher than the control6.82%. The plants total nitrogen, absorption amount of¹⁵N and¹⁵N fertilizer use efficiencywere the largest in the treatment2, and the difference between the two, respectively487.7g,4.75g,23.73g.2、Hydroponic experiments show that, compared with the control, the silicon applicationsignificantly improved the content of chlorophyll a, and the chlorophyll a content in treatment2was the largest. After the addition of silicon, with the increase in the number of processingdays, the chlorophyll a content was increased and then decreased. In the25days the content of chlorophyll a in the three treatments were maximum, compared with the control,respectively,43.32%,18.83%and17.75%. Chlorophyll b and total chlorophyll content alsoshowed similar trends. With the increase of the treatment days, T1, T2and T3treatments inleaf SOD activity was significantly increased and then decreased trend. Compared with thecontrol, the treatment2was significantly higher than other treatments. POD and CAT activityalso showed similar trends. The nitrate content in the treatment were increased and thendecreased. In the25days, The nitrate content in the three treatments were maximum.Compared with controls, the addition of silicon could improve the content of the nitratecontent of the Malus hupehensis, and in the treatment2was the best. The treatment2was thehighest and the Treatment3was the lowest, and were respectively79.04%,39.744%and69.26%,34.50%.3、 The NDFF value of different treatments showed the consistent laws, namelyabove-ground underground. The overall trend of Malus hupehensis in different silicontreatments was with the increase of silicon, nitrogen uptake first increased and then decreased.The treatment2had the highest plant total nitrogen,1.46g; the Treatment3was lowest,0.70g.¹⁵N distributions in different silicon content processing plants were the same, bothaboveground than belowground. With silicon amount¹⁵N distribution amounts of theaboveground were the first increased and then decreased trend. Difference analysis:significant differences were between the T2and T1and T3treatments. Compared with thecontrol, the aboveground¹⁵N distribution rate in the T1and T2treatments were significantlyincreased and T2treatment up to73.86. With the different silicon content, the¹⁵N allocationrate in the aboveground and the belowground ranging from1.89to2.82. The¹⁵N utilizationratio in T2was the largest,8.68%; T3was the lowest,3.64%and significant differencebetween the two.