Abstract: To investigate the ultramicro structure changes of palisade cell in flue-cured tobacco leaf during growth and development,the chloroplast,starch grain,osmiophilic globule and vacuole were observed by transmission electron microscope via field experiments.The results showed that the chloroplasts in palisade cell was in developing and photosynthesis began when leaf was 10 cm in length;small vacuoles had fused into a single large central vacuole when leaf was 20 cm in length;at 50 cm leaf length,the structure of chloroplasts matured,and cells entered a florescent stage,in which synthesis was dominant.After tobacco leaf reached 60 cm in length,chloroplasts gradually degraded along with rapid enlarging and increase of the accumulated starch grains,and the osmiophilic globules increased obviously.In ripe leaf,plentiful starch grains and osmiophilic globules accumulated in chloroplast.