Abstract: Abstract: In order to explore the influence of different nitrogen levels and equal nitrogen deficiency at maturing stage on plastid pigment metabolism in flue- cured tobacco and select the key genes closely related to nitrogen levels of plastid pigment transform and degradation metabolism，pot experiment was conducted． The ultrastructure，net pho- tosynthetic rate and the plastid pigment contents were compared in flue- cured tobacco NC297．The expression levels of several key genes related to plastid pigment metabolism were also analyzed．The results showed that on the 30 d and 60 d after transplanting，the contents of plastid pigment in tobacco leaves increased with the rising of the nitro- gen level．The net photosynthetic rates were consistent with the variation of plastid pigment contents．The contents of osmiophilic granule and thylakoid lamella of chloroplast were improved，while the aging and degradation rates de- layed with the rising of nitrogen level during the maturity period．The expression of nicotiana tabacum senescence- specific cysteine protease (CP1 ) was gradually decreased．The expression of pheophorbide a monooxygenase (PAO) in super high nitrogen treatment N1 was siginificantly higher than other treatments at the end of the mature stage．Expression peaks of－ carotene desaturase (ZDS)，carotenoid cleavage dioxygenases， CCDs and 9- cis- epoxy carotenoid dioxygenase (NCED) were postponed with the rising of the nitrogen level．In conclusion，the timing of expression peak of gene PAO，ZDS，CCDs and NCED can be used as the index for the evaluation of nitrogen nutri-tion conditions of the tobacco plants．

Key words: Flue- cured tobacco, Nitrogen level, Plastid pigment, Ultrastructure, Gene expression

CLC Number: 

• S572