Structural and Functional Strategies in Cenchrus Species to Combat Environmental Extremities Imposed by Multiple Abiotic Stresses

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.