[Objective]This study was to reveal the physiological and ecological mechanism of growth and development of test-tube seedlings.[Methods]Leaf stomata of test-tube seedlings of D.loddigesii and D.candidum at different growth and development stages were observed under scanning electron microscope,and their fluorescence induction response curve was assayed by using modulate fluorometer.[Results] At each growth and development stage,D.loddigesii test-tube seedling has a higher leaf stomatal density over D.candidum,while a lower stomata opening rate.Along with the growth,the size of stomata of both D.loddigesii and D.candidum did not change obviously,but their stoma density increased by 83% and 17.6% respectively.Leaf stomata opening rate reached the highest at the age of 240-day-old.Under the conditions of three settled light intensities,stomatal opening degree of D.loddigesii was increased by the intensity of illumination,the maximum aperture occurred at the light intensity of 54 μmol/m2·s.Given the same culture condition,both the maximum electron transport rate（14 μmol/m2·s）and light saturation point（318 μmol/m2·s）of D.loddigesii test-tube seedling are lower than that of D.candidum（20 μmol/m2·s,483 μmol/m2·s）.Moreover,the potential photosynthetic capacity of D.loddigesii is relatively poor.[Conclusion]The photosynthetic rate varies among different species of Dendrobium,which could be attributed to their different stomatal characteristics.Usually,the light intensity of tissue culture chamber is set up as 27 μmol/（m2·s）,where both D.loddigesii and D.candidum do not acquire an optimal state for their leaf stomatal opening.Considering the characteristics to select suitable culture condition,the stomatal aperture and photosynthetic rate could be enhanced,which can promote the growth and development of test-tube seedlings.
