| Tea plant is a typical fluoride-accumulating plant.Drinking brick tea with high fluoride content can easily lead to fluorosis for a long time.At present,there are few reports on the transport pathway of fluorine in tea plants and the effects of selenium-fluoride interaction on the physiology of tea plants.In this experiment,Shuchazao clone was used as material to study the transport mechanism of fluorine in tea plant by isotope tracer imaging technology,and then the effects of selenium-fluoride interaction on fluorine,selenium,other mineral elements and antioxidant enzymes in tea plant were studied.This study provides direct evidence for the transport of fluorine in tea plants,and preliminarily explores the effects of selenium on fluorine,other mineral elements and antioxidant enzymes in tea plants,and provides theoretical basis for reducing fluorine content in tea.In view of the above problems,the specific research contents and results are as follows:1.Positron emission tomography(PET)and fluorescence probe technology were used to study the absorption,transportation and distribution of fluorine in tea plants.The results showed that:(1)The root system of tea plant had retention effect on fluorine.After about 1.5 hours of transportation to the shoot,fluorine was mainly transported up through the xylem in the stem,and the transportation speed was slow.At the end of 8 hours of monitoring,fluorine activity was not monitored in the leaves.Nodal sites of tea stems may play an important role in the transport and storage of fluorine.(2)The experiment of tea stalk feeding showed that fluoride was mainly transported downward along the stem,and had been transported to the root about 7 minutes.The transporting speed was faster,but the activity of fluoride was not monitored in the root at the end of 8 hours monitoring.In the transportation and distribution of fluorine to the blade,the first one is to transport to the top blade with lateral characteristics,that is,to transport preferentially to the same side(feeding point on the same side).2.The effects of selenium and fluoride on the activities of fluorine,selenium,mineral elements and antioxidant enzymes in tea plants were studied by hydroponic experiment.The results showed that:(1)Selenium addition could reduce the fluorine content in tea leaves.The fluoride content of old and young leaves of tea plants treated with selenium was lower than that of control group.The fluoride content of tea roots increased with the increase of selenium concentration in fluoride treatment,which may be that selenium promoted the absorption of fluoride by tea roots or that selenium had a certain retention effect on fluoride.(2)Selenium and fluoride treatments had significant effects on selenium content in tea plants.Selenium content in tea plants(roots,old leaves and tender leaves)gradually increased with the increase of Se concentration,and Se accumulation in tea plants,especially in old leaves,was promoted by low concentration of fluoride(5.0 mg/L).(3)Calcium(Ca)content in roots,old leaves and tender leaves of tea plants increased with the increase of fluoride concentration,while Ca content in roots and old leaves decreased with the increase of selenium concentration,while that in tender leaves increased with the increase of selenium concentration.The interaction of selenium and fluoride inhibited the accumulation of manganese(Mn)in tea roots and old leaves.The interaction of selenium and fluoride increased the accumulation of copper in tea plants.Fluoride promoted the absorption of Al,Cd and Pb in tea plants,while selenium inhibited the accumulation of Al,Cd and Pb.(4)The activities of antioxidant enzymes(SOD,POD and CAT)in tea leaves increased first and then decreased with the increase of fluoride concentration.At the same concentration of fluoride,the activities of SOD and POD in tea leaves increased first and then decreased with the increase of selenium concentration,and the activities of SOD and POD were the highest at 0.25 and 0.5 mg/L of selenium,respectively,while the activities of CAT increased gradually with the increase of selenium concentration at 0 and 5.0 mg/L of fluoride treatment,and then decreased with the increase of selenium concentration at 20 mg/L of fluoride treatment.The results showed that low fluoride or selenium increased the activity of antioxidant enzymes in tea plants,while high fluoride or high selenium decreased the activity of antioxidant enzymes. |
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