| Camellia sinensis (L.)cv. Pingyangtezao was studied as material in this paper. With the basal fertilization in 2009 autumn, the chemical fertilizer NPK match was schemed and carried out in the spring, summer and autumn of 2010. In this plan, five treatments CK,N200,N300,N400,N500 was designed, and applied with the pure nitrogen fertilizer variation respectively with 0, 200, 300, 400 or 500kg per hectare per year. The propotion of N P2O5 and K2O was 3:1:1; the season variation of spring summer and autumn was 3:2:1. With the results of the determination and comparison of the key enzyme activity and tea quality components, the influence of fertilization factors on the tea carbon, nitrogen metabolism and tea quality had been investigated, which could be used for guiding rational fertilization for tea garden management. The results were as follows:1. Comparison of carbon metabolism enzyme activityNPK match can increase glycolate oxidase (GO) activity. There is little difference in GO activity among the three seasons, the activity in spring is a litter higher than that in other seasons possibly because of temperature, fertilization, nutrient content in the tea and soil, growth condition and so on.NPK match can improve invertase (INV) activity, but the activity is different in each season. Overall, INV activity in autumn is higher than in spring and summer, and the activity in summer is lowest. INV activity of N300 (300kg nitrogen per hectare per year) is the highest in the three seasons. The increase of INV activity can facilitate carbon metabolism and generate large amount of carbohydrate, providing more carbon frame for tea growth and other organic synthesis, which is beneficial to the transformation and use of assimilation production.2. Comparison of nitrogen metabolism enzyme activityNPK match can increase Glutamine synthase (GS) activity obviously, thus improves nitrogen assimilation rate. GS activity in the tea first rises and then declines with the increase of fertilizer. N300 (300kg nitrogen per hectare per year) has the highest GS activity of all the three seasons.NPK match can improve nitrate reductase activity (NR) in certain limitation, but excessive fertilization would inhibit NR activity. All of the three seasons, GS activity of N400 (400kg nitrogen per hectare per year) is significantly higher than other treatments. NR is the key enzyme of nitrogen assimilation, its activity strengthening can promote nitrogen metabolism and photosynthetic carbon metabolism, and then improve the quality of tea.NPK match significantly enhances Glutamic-oxalacetic transaminease (GOT) and glutamic-pyruvic transaminase (GPT) activity. GOT activity in spring rises following the adding of fertilization; GOT and GDP activity improves with the adding of fertilization in certain extent, and then starts dropping. In spring, GOT activity of N500 (500kg nitrogen per hectare per year) is the highest, the GPT activity of N200 (200kg nitrogen per hectare per year) is the highest; in summer, N500 (500kg nitrogen per hectare per year) has the highest GOT and GPT activity; in autumn, both GOT and GPT activity of N200 (200kg nitrogen per hectare per year) is the highest.3. Comparison of enzyme activity quality relatedIn spring and autumn, Phenylalanine ammonia-lyase (PAL) activity of N500 (500kg nitrogen per hectare per year) has increased obviously, however PAL activity of N500 (500kg nitrogen per hectare per year) is lower than control in summer. In spring, N500 (500kg nitrogen per hectare per year) has the highest PAL activity; PAL activity of N400 (400kg nitrogen per hectare per year) is the highest in summer and autumn. In the summer treatments, PAL activity does not change significantly maybe relating to the strong light, high temperature and heavy rainfall.NPK match can significantly increaseβ-glucosidase activity, the activity in spring and summer is obviously higher than that in autumn.β-glucosidase activity of N300 (300kg nitrogen per hectare per year) is the highest in all the three seasons.4. Comparison of tea pigmentNPK match can increase the content of tea pigment, and it is beneficial to photosynthesis and tea color. In different seasons, the content of tea pigment could vary in certain range. In spring, the content of tea pigment is all obviously higher than control and the content of N400 (400kg nitrogen per hectare per year) is the highest. In summer, the change of chlorophyll content is evident, however carotenoids content has not changed much, in which N500(500kg nitrogen per hectare per year ) has the highest chlorophyll content, and N400(400kg nitrogen per hectare per year ) have the highest carotenoids content. In autumn, total chlorophyll content does not change significantly and the content of chlorophyll a, chlorophyll b and carotenoids changes remarkably; among them, N500 (500kg nitrogen per hectare per year) appears with the highest content of chlorophyll a, total chlorophyll and carotenoids, N300 (300kg nitrogen per hectare per year) with the highest content of chlorophyll b. 5. Comparison of tea aroma componentNPK match can improve tea aroma compositions varieties, and with the most species in spring. In spring and summer, N500 (500kg nitrogen per hectare per year) treatment has the most species of tea aroma component, the total species is 17 and 12 respectively; in autumn, N400 (400kg nitrogen per hectare per year) treatment has the most species of tea aroma component, the total species is 16. The autumn treatment N400 (400kg nitrogen per hectare per year) also has more species of aroma component, maybe the climate characteristics in autumn is kindly helpful for special aroma compositions formation of autumn tea.6. Comparison of tea taste ingredientIn different seasons the response of tea taste ingredient content to fertilization is not quite the same. Within the certain scope of fertilization, tea taste ingredient content increases following the adding of fertilization, and then begins to fall to the specific point. In spring, N300 (300kg nitrogen per hectare per year) has the highest content of water extract, amino acids, caffeine, theanine, and tea polysaccharide, which is suitable for manufacturing green tea. In summer, the content of amino acids, caffeine, soluble protein and vitamin C in N300 (300kg nitrogen per hectare per year) is the highest, and it is fit for green tea. In autumn, there is the highest content of amino acids, theanine, tea polysaccharide and soluble sugar in N200 (200kg nitrogen per hectare per year) for making green tea; N400(400kg nitrogen per hectare per year) has the highest content of water extract, tea polyphenols, caffeine and vitamin C, suitable for manufacturing red tea.7. Comprehensive comparison of enzymes and qualityThere is the highest content of Amino acid and the lowest content of tea polyphenols in spring, just the reverse in autumn, by contrast, the content in summer is between the two, thus making spring tea tasted fresh and cool, summer and autumn tea tasted strong but not fresh. The impact of NPK match on the tea quality and enzyme activity is different in each season, but overall, N300 (300kg nitrogen per hectare per year) and N400 (400kg nitrogen per hectare per year) is more suitable for tea growth and improving the quality of tea. In the three seasons the response of tea quality contents and key enzyme to fertilization is not quite the same, probably because of growth condition, light, temperature, water and so on. |
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