Study On The Photosynthetic Characteristic And Nitrogen Metabolism In Different Nitrogen Treatment Of The Flue-cured Tabacco

Nitrogen nutrition plays a crucial part in the growth and quality formation of flue-cured tobacco,which has become an hotspot issues in tobacco cultivation, thus more attention be given by foreign and domestic experts in this field. .This experimental material was CB-1 which was the main tobacco variety in Fujian province, China. The physiological characteristic and nitrogen metabolism in different leaf-position of CB-1 within different nitrogen rates were studied. which aimed at looking for the suitable change law of nitrogen and carbon metabolism, and high quality and sutable produce of flue-cured tobacco. The experimental resultes indicated:1. To some extent,along with the increasing of nitrogen fertilization,the content of the content of Chla, Chlb and Chla/Chlb in different leaf-position tobacco significantly increased. The contents of Chla and Chlb were decreased constantly in the tobacco growth period, but its rates and extent decreased with the increasing of nitrogen amount.2. Along with the ascent of the leaf-position, the RUBPCase activity increased,and with the leaf riped,the RUBPCase activity decreased. The high levels of applied nitrogen, can protected observably the RUBPCase activity in the whole growth period and keep the high RUBPCase activity in longer time than others, then protect the Photosynthesis.3. The high levels of applied nitrogen is helpful to protect photosynthetic apparatus, highten net photosynthetic rate, photochemical quenching and the content of surose, lower non- photochemical quenching.But it never had significantly influenced onФPSII and Fv/Fm.4. Along with the aging of the leaf, key enzymes activities of nitrogen metabolism and the content of free amino acid in all treatments decreased. The high levels of applied nitrogen is helpful to increase the glutamineα-ketoglutarate aminotransferase activity, restrain the glutamine invertase activity and protect the synthesis of free amino acid. But it never had significantly influenced on glutamine synthetase activity.5.There are high positive correlation between nitrogen levels and the nicotine and total nitrogen in different leaf-position of cured tobacco. There are no significantly correlation between nitrogen levels and total sugar and reducing sugar in middle and lower leaves. Total sugar and reducing sugar in upper leaves significantly decreased along with the increasing of nitrogen fertilization.In a word, nitrogen rate ,which ranged from 97.5 kg/hm2 to 117 kg/hm2, is helpful to increase the content of chla and chlb,the RUBPCase activity, net photosynthetic rate , the content of nitrogen compounds in cured tobacco , the glutamineα-ketoglutarate aminotransferase activity and the content of free amino acid and protect the chlorophyll a/chlorophyll b .It also can significantly increase the photochemical quenching in the middle and upper leaf and the content of surose in upper leaf and lower non- photochemical quenching.But it never had significantly influenced on glutamine synthetase activity,ФPSII ,Fv/Fm and total sugar and reducing sugar in cured tobacco. From tobacco sensory, it slowdown the maturation of tobacco leaf. No fertilization significantly restrained the synthesis of the chlorophyll and the glutamineα-ketoglutarate aminotransferase activity, promoted the degradation of photosynthetic apparatus, increased the glutamine synthetase activity and the glutamine invertase activity, and reduced the content of free amino acid, the plant showed premature senescence. Nitrogen rate ,which ranged from 58.5 kg/hm2 to 78 kg/hm2, cured tobacco leaf have the proper yield , higher quality and comparatively suitable chemical composition in different leaf position. To some extent, its indexes of photosynthesis and nitrogen metabolism can be used as reference index, which can distinguish normal conversion between carbon and nitrogen metabolism.