Effects Of Different Nitrogen Forms And Different Light Qualities On Enzymes Involved In Nitrogen Assimilation Of Flue-cured Tobacco

Through the Field and solution culture experiments,we studied the effects of different nitrogen forms and topping on enzymes ammonium assimilation metabolism, effects of different light qualities on key enzymes involved in ammonium assimilation and carbon metabolism of flue-cured tobacco. we also prelimmary researched on the method of isolation and purification of the key enzymes ammonium assimilation—Glutamine synthetase(GS; EC 6.3.1.2) isozyme of flue-cured tobacco leaves. The results were as follows:1 Effects of different nitrogen forms on key enzymes involved in ammonium assimilation metabolism of flue-cured tobacco were studied. The results showed that the NR activity increased in roots and in leaves under NO₃^--N treatment, the NH₄⁺-N treatment can enhance the GS activity and the soluble protein content in roots and leaves. Different nitrogen forms had different effects on the AS and GOT activity in the different organ. Under the NO₃^--N treatment, the AS and GOT activity were higher in leaves but the NH₄⁺-N treatment can enhance the AS and GOT activity in roots.2 The activities of GS and AS after topping are higher than no topping in flue-cured tobacco. The activity of GS in the leaf of the fifth day is higher 48.1 % after topping than no topping; the activity of GS in the roots is higher 55.9% than the no topping treatment, but the activity of GS of the topping treatment in roots increases rapidly and the activity of GS in leaves begins increasing a day after topping. After topping the activity of AS also increases in tobacco roots and leaves but the change of the activity of AS is later than the activity of GS. This paper shows topping changes the relation of the sink-source in tabacco, accelerates nitrogen metabolizability and growth in roots accordingly composes more nicotine into tobacco leaves.3 Isolation and purification of GS isozyme of flue-cured tobacco leaves were studied. We confirmed the ammonium sulfate density is 20%-80% for GS isozyme of flue-cured tobacco leaves through the ammonium sulfate precipitation separation experiment. We found two GS isozyme after the DEAE-Sephcel ion-exchange chromatography and analysed the molecular weight probably was 43-45KD by the SDS-PAGE examination. 4 Effects of different light qualities on key enzymes involved in ammonium assimilation and carbon metabolism of flue-cured tobacco were studied. The results showed that effects of different light qualities on the NR activity was control>bule film>red film in leaves and the tobacco root NR activity in red and blue light treatment was not significant. The GS activity was bule film > control >red film and the bule film treatment's GS activity was higher 61.8% than red film treatment in leaves, was higher 29.2% than red film treatment in roots. The bule film treatment had highest soluble protein content and AS activity in leaves and roots. Different light qualities had different GOT activity of flue-cured tobacco leaves and roots, the result were control > bule film >red film in leaves and control > red film > bule film in roots.4 Effects of different light qualities on photosynthesis and chlorophyll fluorescence of flue-cured tobacco leaves were studied. The results showed that the chlorophyll a , chlorophyll b and the total chlorophyll were all promoted under red film(620-780nm), chlorophyll a/b was promoted under blue film (400-450nm).