Effects of light and temperature stress on photosynthesis of flue-cured tobacco at mature stage

To investigate the effects of environmental stress on flue-cured tobacco at mature stage, a pot experiment using Yunyan 87 as an experimental leaf was conducted to simulate high temperature and high light intensity at late growth stages in Hunan tobacco-planting areas. The effects of light and temperature stress on the photosynthetic characteristic of Yunyan 87 at mature stage were analyzed. The results showed that:1) With the variation in light intensity, the transpiration rate, stomatal conductance and net photosynthetic rate of the flue-cured tobacco differed significantly at normal temperature, and peaked at 80 000 lux; while all of them significantly decreased at high temperature. 2) Generally, at the same light intensity, the transpiration rate, stomatal conductance and net photosynthetic rate of the tobacco decreased and intercellular CO₂ concentration increased at high temperature. 3) Under high light and temperature stress, the transpiration rate, stomatal conductance and net photosynthetic rate significantly decreased, intercellular CO₂ concentration increased, and the photosynthetic capacity reduced. 4) Correlation analysis indicated that net photosynthetic rate significantly positively correlated to stomatal conductance of the flue-cured tobacco and transpiration rate positively correlated to net photosynthetic rate and stomatal conductance.