| Abstract: | The overall objectives of the study were to determine (i) if genotype variation of stomatal sensitivity to water deficit exists in Sorghum bicolor (L.) Moench and (ii) the extent to which stomatal closure contributes to the reduction in photosynthetic rate in response to water deficit, in some selected sorghum genotypes. All the plants tested were in the vegetative phase of growth. They were grown and tested in a controlled environment chamber under conditions of high irradiance (equivalent to full sunlight), a 12 hour photoperiod, 30C air temperature, 27C dewpoint temperature, and 320 ppm CO₂. Twenty-three genotypes were first screened for stomatal sensitivity to decreasing soil water potential, by growing a single plant of each genotype in a pot along with a single plant of a control genotype which was common to all pots. A genotype's sensitivity was then measured in relation to that of the control genotype grown in its pot. This test showed that considerable variation far stomatal sensitivity existed among the 23 genotypes. The relationship between leaf diffusive conductance and leaf water potential was obtained far Alpha and Shallu which were found to be sensitive in the screening test and for I.S.1598C and H35-1 which were found to be Insensitive. This test confirmed the results of the screening test. It showed that for each genotype the relationship between leaf diffusive conductance and leaf water potential was best fitted with a second order polynomial equation. ... |
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