The Effect Of Selenium And Zinc Interaction On Nutritional Effect Of Tea Plant Under Hydroponics

The growth of tea, the formation and accumulation of tea quality ingredients are impacted by selenium(Se) and zinc(Zn). But the discussion of the effect of zinc and selenium interaction on tea nutritional effect and its mechanism is still rare. In this study, the representative kind of Mengding mountain tea, Mengshan 9(two-year-old) was chosen as the experimental material. Based on hydroponics experiment through spring, summer and autumn, the effect of zinc and selenium interaction on the growth of tea, its root activity, metabolism and the absorption and accumulation of elements were studied. The main findings are as follows:1. The effects of single-Se with different concentrations on tea germination are different. The tea buds can be increased by the treatment of mid and low concentrations of Se(Se<8.00mg/L), while it will be restrained by high concentrations of Se(Se>8.00mg/L). Single-Zn treatments all benefit the increasing of tea buds. Se/Zn interaction with the concentration of Zn<0.20mg/L and Se<8.00mg/L has best effect on tea germination.Se and Zn has certain effect on the quantity and extending speed of new tea root. Compared with the control, the quantity of new tea root will reduce along with the increase of Se concentrtion, and the new roots are sparse and short. And there are only 5 roots per plant when the concentration of Se>8.00mg/L. Single-Zn treatment promotes the growth of new root. When the concentration of Zn is 0.10-0.40mg/L, it benefit the growth of tea root most, the new roots are intensive, and there are 35.7 roots per plant. There is no significant difference of the new root quantity, when zinc and selenium interaction treatment is with the low concentration of Se/Zn(Se<4.00mg/L and Zn<0.10mg/L), the longest root is 2.7 cm, and the average number of root per plant is 17.2～25.6. When zinc and selenium interaction treatment is with the concentration of 8.00Se/0.20Znmg/L, it has most positive effect on the extending and quantity of tea root. As far as root activity, compared with the control, the tea root activity declines slightly, when Se concentration<8.00mg/L. And the tea root activity declines rapidly when Se concentration>8.00mg/L, the biggest drop of it is 15.48%, it is indicates excessive Se restrains the tea root activity very obviously. The activity of tea root increases along with the increase of Zn concentrtion, it reaches the maximum when Zn concentration is 0.40mg/L, and it increased 6.76% of the control. There is no significant difference of tea root activity with the treatment of Zn(0.05～0.40mg/L).Zinc and selenium interaction effects more on tea root activity than single-Se or single-Zn. When Interaction with Se(4.00～8.00mg/L) and Zn(0.05～0.20mg/L), the activity of root is higher than the control. With certain concentration of Zn, the activity of tea root increases first and then decreases along with the increase concentration of Se, and the difference reached at a very notable level(P<0.01). It gets to maximum with Se4.00 mg/L, but the activity reduces when the concentration exceeds that level, and it turns to minimum with Se16.00 mg/L. When the concentration of Se is between 4.00～16.00mg/L, the activity of tea root increases first and then decreases along with the increase concentration of Zn, and Dynamic high-values appear when the concentration of Zn is between 0.05～0.20mg/L.2. Single-Se can increase the content of chlorophyll a, and the increasing degree gets to the biggest with Se4.00mg/L. Compared with the control, it increased by 43.15%, but single-Se has little effect on chlorophyll b. In summer and autumn, each index value of chlorophyll is lower than in spring under the effect of single-Se. The effect of single-Zn on the content of chlorophyll in spring tea is slight, but it still shows the content of chlorophyll is highest in summer, and in spring it is higher than in autumn on the whole. In Se/Zn interaction treatment, with certain concentration of Zn, the content of chlorophyll b and the gross both increase first and then decrease along with the increase concentration of Se, and the critical point is Se4.00mg/L. When Se(4.00～8.00mg/L) and Zn(0.20～0.30mg/L) match, it benefits the increase of tea chlorophyll content mostly.In single-Se treatment, the photosynthetic rate of tea increases with the increase concentration of Se in spring, summer and autumn. There is a positive correlation of them, and the photosynthetic rate gets to maximum when the concentration of Se is 16mg/L. The photosynthetic rate is highest in summer, and in autumn it is higher than in spring. Compared with the control, the transpiration rate of tea decreases with the increase concentration of Se in spring and autumn. It promotes the tea net photosynthetic rate(R=-0.83**), and increases water utilizing rate of leaf. And Se treatment in spring and autumn is not significant(P<0.05). In single-Zn treatment, the photosynthetic rate gets to maximum in summer, and the difference is slight between spring and autumn(P>0.05). Zn effects the photosynthetic rate notably(P<0.05), and the photosynthetic rate can be improved by the increase concentration of Zn. With the treatment of Zn, the leaf intercellular CO₂ concentration decreases when the concentration of Zn increases, but the leaf intercellular CO₂ concentration is highest in summer, and in autumn it is higher than in spring on the whole. Zn reduces the leaf intercellular CO₂ concentration and promotes the tea net photosynthetic rate, however, such effect of Zn weakens along with the increase of its concentration.Low concentration of Se/Zn treatment is not conducive to the photosynthesis of tea. Tea net photosynthetic rate increases by increasing the supply of Se. The leaf intercellular CO₂ concentration can be reduced and net photosynthetic rate can be improved by Se, and also the water utilizing rate of leaf can be promoted, In summer and autumn, the effect of Se/Zn interaction on tea is similar to it is in spring. There is no significant effect on tea photosynthesis with the interaction of low concentration of Zn and different concentration of Se.In single-Se treatment, amino acids content in spring tea increases first and then decreases along with the concentration of Se. It gets to maximum at Se2.00mg/L, and maintains stability in the range 0 f Se8.00～16.00mg/L. The changing trend of summer tea is similar to the situation of spring tea. When the concentration of Se is 16.00 mg/L, the amino acids content turns to minimum. It indicates high concentration of Se in is not good for the formation and accumulation of amino acids. The changing trend of amino acids content in autumn tea is contrary to the spring tea, it performs to decrease first and then increase.In Zn(0～0.40mg/L), the amino acids content in spring tea can be increased, but there is no significant effect on the amino acids content in summer tea. In Zn 0.02～0.10mg/L, the amino acids content in autumn tea decreases slightly, and then increases with the increasing supply of Zn.In Se/Zn interaction, under the treatment of mid and low concentration(Se<8.00mg/L), it is good for the increasing of amino acids content in spring and summer, but when it exceeds the concentration, there will have negative effect on the content. When it is under the treatment of low concentration of Se(2.00mg/L), the amino acids content in autumn tea is positively correlated with the concentration of Zn. And the increasing extent is obviously higher than the content of spring and summer tea. But when it is under the treatment of high concentration of Se(Se>8.00mg/L), the amino acids content decreases with the increase of the concentration of Zn instead.4. Single-Se treatment promotes the formation of polyphenol in new tea buds. The content of polyphenol increases along with the increase of the concentration of Se, but the difference is not notable among treatment levels. In single-Zn treatment, the maximum of polyphenol content in spring and summer tea appears at Zn 0.10mg/L. Compared with spring and summer tea, the changing of polyphenol content in autumn tea trends to be stable. In proper concentration of Se/Zn interaction, it has obvious positive effect, but the effect on the whole is not as notable as it is in single treatment.5. The analysis results of the effect of Se/Zn interaction on the ability of each part of tea to absorb and metabolize S, Zn and Se indicate that in single-Se treatment, the accumulation of S in tea tends to be basically the same in the three seasons. Se has antagonism effect on absorption of S, but it only appears when the concentration of Se is high(Se>8.00mg/L). In single-Zn treatment, the content of S in new leaves, main roots and stems can be increased, so it has positive effect. In spring, the content of S in new leaf gets to maximum at Zn 0.4mg/L, and it is higher than in summer and autumn. In Se/Zn interaction(2.00/0.02mg/L), the content of S in new leaves and stems gets to maximum, while the content of S in old leaves gets to maximum at(4.00/0.02mg/L). It is best for tea root to absorb S in mid concentration of Se/Zn interaction(Se2.00～8.00 mg/L)/(Zn0.10～0.20mg/L). The curves fitting with S absorption in each part of tea in summer and autumn are similar to the curve in spring. There is no change in regression model according to the variety of the season, it only reduces the absorption of S in different degrees. New leaves and stems are not the main parts of tea to accumulate S. In summer and autumn, the Se content in each part of tea is obviously lower than in spring. The effect of Se/Zn interaction on the absorption and accumulation of Se in each part of tea can be fitted by a quadratic equation with one variable. The absorption of Se has the trend to increase first and then decrease along with the increase of Se/Zn ratio. Mid concentration treatment of Se/Zn(Se4.00～8.00mg/L) and(Zn0.10～0.20mg/L) benefits the absorption and accumulation of S and Zn. Mid and low concentration treatment of Se(2.00～8.00mg/L)Zn(0.10～0.20mg/L) is good for the absorption and accumulation of Se. And high concentration treatment of Se will restrain the absorption of Se.