The Expression of Dehydrin Genes and the Intensity of Transpiration in Drought-stressed Maize Plants

The stress reaction of maize plants was evaluated in relation to drought stress intensity and to growth stages by assessing the transpiration intensity and the expression of two dehydrin genes, DHN1 and DHN2. The maize plants were grown under four different watering conditions: well-watered (control), mild stress, moderate stress and high stress. The sap flow values were taken as an indicator of plant stress reactions at the transpiration level. A significant correlation between the average diurnal values of sap flow and the volumetric soil moisture appeared only for the moderate stress condition (R = 0.528) and for the high stress condition (R = 0.395). Significant increases in the expression of DHN1 and DHN2 (DHN1 = 105-fold and DHN2 = 103-fold) were observed primarily for the high stress condition compared to the control. Differences in the stress reactions at the DHN1 gene expression level were detected for all the experimental drought stress conditions. A relatively close relationship between the levels of expression of both genes and the values of the sap flow was observed during the initial stage of the stress (R = –0.895; R = –0.893). The severity of water stress and transpiration intensity significantly affected certain biometric and yield parameters of maize. Higher DHN genes expression at the ripening stage was related to lower grain and dry biomass yield. The results indicated that DHN gene expression assessment in maize and evaluation of the changes in transpiration expressed by the sap flow could be considered appropriate indicators of stress intensity while the DHN gene expression assessment appeared to be more sensitive than evaluation of the changes in transpiration, mainly in the initial phases of stress response.