A study on photosynthetic characteristics of different Salvia miltiorrhiza varieties.

To provide basic data for planting S.miltiorrhiza cv.silcestris and S.miltiorrhiza cv.sativa,their photosynthetic characteristics were studied.A LI-6400XT portable photosynthesis system was used to measure diurnal dynamics of the photosynthetic characteristics and light-response curve of photosynthesis.The light compensation point and light saturation point of S.miltiorrhiza cv.sativa were lower than those of S.miltiorrhiza cv.silcestris.The apparent quantum efficiencies were higher than 0.06,which showed that they had a strong utilization efficiency in weak light.Diurnal course curves of their net photosynthetic rates had two peaks,one occurred at 11:30 and the other at 14:30.Their midday depression occurred at 13:00.The midday depression of S.miltiorrhiza cv.silcestris was due to stomatal limitation while that of S.miltiorrhiza cv.sativa was not.Diurnal course curves of their stomatal conductance and transpiration rate had a single peak.The midday depression of S.miltiorrhiza cv.sativa was deduced to be due to localized water stress in leaves when the transpiration rate was high at midday.To ease midday depression and increase production of S.miltiorrhiza cv.sativa,some tall crops should be intercropped.