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The prevalence of antibiotic-resistant airborne bacteria was examined at seven different localities along the urban roads of Rahim Yar Khan. Airborne bacteria from the respiratory zone were sampled three times a day and five times a year using gravity deposition on nutrient agar plates. Six antibiotics – ampicillin, penicillin, streptomycin, clarithromycin, ciprofloxacin, and ceftriaxone – were used to screen antibiotic-resistant airborne bacteria. In this study, antibiotic-resistant airborne bacteria were detected at all sampling sites, with the highest antibiotic resistance observed in a residential area (RA). The airborne bacteria showed maximum resistance to streptomycin. The airborne bacteria of winter season were more resistant (43%) to tested antibiotics than airborne bacteria of any other season. These results specify that the pollutant exposure risk factor is different at each sampling site because of the potential contribution of various point sources. These findings of the study will be helpful to public health professionals and policy makers to develop effective interventions to combat adverse health impacts of bio-aerosols on the local population.
Populations of three salt tolerant forage grasses (Cynodon dactylon, Imperata cylindrica, and Sporobolus arabicus) were collected from the salt-affected soils of the Salt Range and normal non-saline soils of the Faisalabad region to assess their mechanism of adaptation to saline stress by determining ion relations and some specific anatomical modifications. The population of S. arabicus from the Salt Range showed increased growth (root and shoot length, and root and shoot dry weights) under saline conditions. Salt tolerance in this species was related to structural modifications such as increased area of root, stem, leaf blade, and leaf sheath for toxic ion accumulation, increased vesicular hair density in leaves and aerenchyma formation in leaf sheath for ion exclusion. Uptake of toxic ions was high in the Salt Range population of C. dactylon and salt tolerance was related to ion exclusion through specific leaf structural modifications such as vesicular hairs. Salt tolerance in the Salt Range population of I. cylindrica was mainly associated with restricted uptake of toxic Na⁺ and Cl⁻ at root level, and accumulation of toxic ions via increased succulence in leaf blades and leaf sheaths in addition to some excretion of toxic ions through leaf sheath aerenchyma.
Some ecologically different ecotypes of Panicum antidotale Retz. were evaluated for drought tolerance in relation to growth parameters and leaf structural modifications. These ecotypes were adapted to normal nonstressed (agricultural field AF, and sludge of disposal channel SDC), drought-stressed (along roadside AR), salinity-stressed (forest plantation FP), waterlogging and salinity-stressed (inside disposal channel IDC), and drought plus salinity-stressed (barren area BA). On the basis of genetic variability in leaf structural modifications, each ecotype adopted specific strategies to tolerate the extremity of drought stress. The AF and SDC ecotypes relied on water conservation and survival rather than growth and structural modifications by developing epidermis and sclerenchyma on both leaf surfaces. The AR developed xerophytic foliar characteristics in addition to maintaining growth and development under stressed conditions like thick leaves, well-developed bulliform cells, and intensive sclerification. The FP ecotype developed efficient strategy for drought tolerance such as reduced and fibrous leaves, smaller metaxylem vessels, and highly developed bulliform cells. The ecotype IDC relied more on water conservation by increasing leaf epidermal thickness and decreasing stomatal area and density. The ecotype BA showed critical structural adaptations such as thin leaves, extremely developed bulliform and reduced metaxylem area, and parenchyma extensions above vascular bundles. Based on the strategies adopted for drought tolerance, the tolerance level of these ecotypes were rated as BA > AR > FP > IDC > SDC > AF.
Three differently adapted populations of sewan grass (Lasiurus scindicus Henr.) were evaluated for structural and functional adaptations to high salinity. The habitats were Derawar Fort (DF, least saline, ECe 15.21), Bailahwala Dahar (BD, moderately saline, ECe 27.56 dS m⁻¹) and Ladam Sir (LS, highly saline, ECe 39.18 dS m⁻¹) from within the Cholistan Desert. The adaptive components of salt tolerance in sewan grass were assessed by determining various morpho–anatomical and physiological attributes. The degree of salt tolerance of all three ecotypes of L. scindicus from the saline habitats was compared in a controlled hydroponic system to evaluate the adaptive components that are expected to be genetically fixed during a long evolutionary process. Salinity tolerance in the most tolerant LS population relied on increased root length and total leaf area, restricted uptake of toxic Cl⁻, increased uptake of Ca²⁺, high excretion of Na⁺, accumulation of organic osmolytes, high water use efficiency, increased root, thicker leaf and cortical region, intensive sclerification, large metaxylem vessels, and dense pubescence on abaxial leaf surface. The BD population (from moderately saline soil) relied on high Ca²⁺ uptake, Na⁺ excretion, epidermal thickness, large cortical cells, thick endodermis and large vascular tissue. The DF population (from less saline soil) showed a significant decrease in all morphological characteristics; however, it accumulated organic osmolytes for its survival under high salinities. Structural modifications in all three populations were crucial for checking undue water loss under physiological stress that is caused by high amounts of soluble salts in the soil.
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