Effect of increasing carbon dioxide on sorghum (Sorghum bicolor)‎ plants under drought stress in the grain filling stage

Abstract EN

Stressed and non-stressed sorghum plants (Sorghum bicolor cv.

Mylon, a local Sudanese cultivar) were subjected to different lev-els of carbon dioxide (CO2), ranging from 10 to 2000 ppm at the grain filling stage.

High CO2 levels assisted stressed plants in terms of high photosynthesis rates (an average of 2.89 µmol mñ2 sñ1 under elevated levels compared to an average of 1.65 µmol mñ2 sñ1 under ambient level), these rates remained constant under a very high CO2 con-centration (1800 ppm).

In addition, increasing CO2 concentrations de-creased the stomatal conductance in stressed plants (from 27 µmol mñ2 sñ1 under ambient level to 15 µmol mñ2 sñ1 under 1990 ppm CO2 concentration) and hence reduction in the transpiration rates (from 0.

68 mol mñ2 sñ1 under ambient to 0.38 mol mñ2 sñ1 under 1990 ppm CO2 concentration).

This together with the high photosynthetic rates, increased water use efficiency (WUE), from 2.

35 under ambient level to 5.26 under 1990 ppm CO2 concentration, which are considered as good factors in increasing sorghum productivity in dry regions.