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Three Cenchrus species (C. biflorus, C. ciliaris, and C. orientalis) were collected from different ecological regions in the Punjab and Khyber Pakhtoonkhwa during July to September 2020 to evaluate tolerance to multiple abiotic stresses (aridity, salinity, and cold). Growth and biomass production was the maximum in C. biflorus, C. ciliaris, and C. orientalis under aridity stress. Aerenchyma formation and vascular tissue increased significantly in roots under aridity. In C. ciliaris, aerenchyma formation was recorded under cold stress. Root vascular tissue was higher under normal conditions (26.7%) and aridity (30.4%) stress in C. ciliaris. Stem parenchyma (29.1%) and vascular tissues (35.5%) showed an increase in C. biflorus under aridity, while mechanical tissue (33.6%) increased significantly under salinity stress. In C. biflorus and C. ciliaris, extensive sclerification was recorded in the stelar region under aridity stress. The stem radius of C. orientalis was greatest under salinity (27.0%) and cold (29.1%) stress, while parenchyma tissue was smaller (12.1%) under cold stress. Leaf thickness generally increased under abiotic stresses, and the maximum (43.0%) thickness was recorded in C. biflorus under aridity stress. Cenchrus biflorus, C. ciliaris, and C. orientalis showed strong association among morphological and leaf anatomical traits under aridity stress. Cenchrus orientalis showed high sclerification outside the vascular bundles of the leaf sheath. In saline conditions, vascular bundles were sclerified and enlarged. In and outside the vascular bundles of leaf blades, extensive sclerification was observed under cold stress conditions. Modifications in structural and functional traits were critical for the ecological success of Cenchrus species for survival in multiple environmental stresses. [ABSTRACT FROM AUTHOR]

Multiple abiotic stresses such as drought, salinity, heat, and cold stress prevailing in natural habitats affect plant growth and development. Different species modify their structural and functional traits to combat these abiotic stresses while growing in stressful environments. Cenchrus species, i.e., Cenchrus pennisetiformis, C. setiger, and C. prieurii are widely distributed grasses found growing all over the world. Samples from natural populations were collected from different ecological regions in the Punjab and Khyber Pakhtoonkhwa that were exposed to aridity, salinity, and cold, while one site was designated as normal control. In the present study, structural and functional modifications of three Cenchrus species under abiotic stresses were evaluated. It was expected that each Cenchrus species may evolve different strategies to cope with multiple abiotic stresses. All Cenchrus species responded differently whether growing in normal environment or stressful conditions. The most remarkable feature for survival in C. pennisetiformis under cold stress was increased inflorescence and increased stem and root lignification. C. prieurii showed better tolerance to saline and cold environments. C. setiger showed better development of leaf sheath anatomical traits. The structural and functional modifications in Cenchrus species such as development of mechanical tissues provided structural support, while dermal and parenchymatous tissues increased water storage capacity and minimized water loss. An increase in the concentration of organic osmolytes and ionic content aids turgor pressure maintenance and ionic content crucial for plant growth and development. It was concluded that structural and functional alterations in all Cenchrus species were very specific and critical for survival under different environmental stresses. The ecological fitness of these species relied on maintenance of growth and biomass production, and the development of mechanical, vascular, dermal and parenchyma tissues under stressful environmental conditions. Moreover, accumulation of beneficial ions (K+ and Ca2+) and organic osmolytes were critical in turgor maintenance, hence survival of Cenchrus spp. [ABSTRACT FROM AUTHOR]