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Published on: September 7, 2015
Divergent physiological and biochemical strategies confer differential salinity and drought tolerance in five
Saira Shafiq1, Muhammad Zia Ul Haq2, Muhammad Shahbaz1
1Department of Botany, University of Agriculture, Faisalabad, 38040, Pakistan.
Abstract:
Soil salinization and drought, exacerbated by climate change, pose a significant threat to global crop productivity, yet the response of weeds, which are key competitors in agro-ecosystems, remains underexplored. This study aimed to evaluate the morphological, physiological, and biochemical responses and stress tolerance of five dominant summer weed species (Dactyloctenium aegyptium, Echinochloa crus-galli, Setaria viridis, Trianthema portulacastrum, and Amaranthus viridis) under salinity (8.0 dS m⁻1) and drought (50.0% field capacity) stress. A controlled pot experiment was conducted to assess plant growth, gas exchange parameters, membrane stability, antioxidant enzyme activities, and oxidative stress markers. Both salinity and drought significantly (p ≤ 0.05) reduced plant dry weight by 4.0-18.0% and 8.0-31.0%, respectively, depending on species. Under salinity stress, Dactyloctenium aegyptium and Echinochloa crus-galli exhibited minimal biomass reductions (4.0% and 5.0%), whereas Setaria viridis showed the greatest decline (18.0%). Under drought, Trianthema portulacastrum was least affected (8.0% reduction), while Echinochloa crus-galli and Setaria viridis exhibited the largest reductions (31.0% and 28.0%). Photosynthetic rate declined by 8.0-15.0% under salinity and 7.0-22.0% under drought, accompanied by significant reductions in stomatal conductance and transpiration rate. Electrolyte leakage increased markedly under stress, reaching up to 94.0%, while relative water content decreased by up to 40.0% under salinity. Antioxidant enzyme activities were significantly enhanced, with superoxide dismutase increasing by 35.0-87.0%, peroxidase by 21.0-76.0%, and catalase by 14.0-50.0%. Malondialdehyde content increased by up to 58.0%, indicating oxidative stress. Overall, species exhibiting greater physiological stability and stronger antioxidant responses showed higher tolerance to stress conditions. These findings provide comparative physiological insight into species-specific adaptive responses to salinity and drought stress and may support future research on weed ecology and stress adaptation under changing environmental conditions.
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