No abstract

The present work is addressed photosynthetic rate, growth rates and quantification of aquaporin genes expression on sunflower plant to examine the expression and regulation profiles of some aquaporins, their role in regulating water transport during salt stress and their role in improving plant tolerance to stresses. The differential regulation of aquaporins might contribute to increased resistance/susceptibility to a specific stress, in a species-specific way. Aquaporins fine regulation helps plants maintain a positive water balance under detrimental environmental conditions. Both down-and up-regulation of aquaporin expression leading to changes in membrane permeability have been described and proposed to be beneficial for plants experiencing water deficit. Plants may decrease the water permeability of their cell membranes to avoid excessive loss of water from the root to the soil and / or aquaporins might play a role in stress avoidance by enhancing root water uptake, when the water potential gradient between soil and root xylem is still favorable. The contribution of both types of responses may depend on the plant species, the intensity and duration of the stress and aquaporin isoform. The salt tolerance is a complex trait but might be partly due to the expression of stress-inducible aquaporin isoforms. The plant shows different expression level of PIP1;5, PIP2;1, PIP2;3, TIP1;1 as well as different water transport activity..

Zea mays L. is less tolerant to drought than Sorghum bicolor L. In the present study, we investigated the response of both plants to drought stress applied under field conditions by withholding water for 10 d. The plant growth in terms of shoot fresh and dry weights was more severely reduced in maize than in sorghum as a result of drought stress, consistently with reduction of leaf relative water content (RWC). Gas exchange was also more greatly inhibited by drought in maize than in sorghum. As a result, the water use efficiency (WUE) of maize was fluctuated according to the time point during the day and in response to drought stress. In contrast, sorghum was able to maintain largely constant WUE during the day in the well-watered plants as well as under drought stress. This may indicate that sorghum was more efficiently controlled its water status in particular water uptake than did maize. Studying the expression of four aquaporin genes (PIP1;5, PIP1;6, PIP2;3 and TIP1;2) revealed that most of the genes responded weakly to drought stress except PIP2;3 which was highly responsive to drought in sorghum but not in maize roots, where it may have supported greater water uptake in sorghum, and thereby maintained higher leaf RWC in sorghum than in maize and hence could account at least in part for the drought tolerance of sorghum as compared to maize. The outcome of this study is that PIP2;3 may have role in drought tolerance and maintenance of the WUE of sorghum plants compared to those of maize.