Browsing by Author "Tsegay, Berhanu A"

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    Biology and resource acquisition of mistletoes, and the defense responses of host plants
    (2022-02-21) Muche, Meseret; Muasya, A M; Tsegay, Berhanu A
    Background Mistletoes are the most successful group of obligatory hemi-parasitic flowering plants that attach to the host via haustorium for obtaining water and minerals. This review aims to assess the current knowledge on mistletoes host plant recognition, haustorium formation, water/minerals acquisition, and host plants’ defense signaling and responses against mistletoe attack. Results Some mistletoes are host-specific while others are generalists occurring on a wide range of vascular plants. The host nitrogen (N) content, parasite–host chemical interactions, compatibility, and dispersal agents are the main determinant factors for host specificity. Mistletoes take up substantial amounts of water and minerals passively via apoplastic routes, and most are xylem feeders, but could shift to phloem-feeding during the physiological stress of the host plants. Current evidence highlighted that cell wall loosening and modification are critical during the development of the haustorium in the host tissue. This is made possible by the application of physical pressures by the developing haustorium and cell wall degradation using enzymes (xyloglucan endotransglycosylases, glucanase, expansins, etc.) produced by the mistletoe. Host plants defend against mistletoe infection mechanically by producing spines, lignin, suberin, etc., which discourages dispersers, and chemically defend by killing the infector or inhibiting the establishment of the haustorium using their secondary metabolites such as terpenes, phenolics, and N-containing compounds. Although the host plants' response to mistletoe attack resembles the response to other biotic stresses, unlike short-term stressors, the effect of mistletoe attack is long-term and depends on the parasite load. Infection by mistletoe leads to water and nutrient stress of the host plant and deteriorates its healthy establishment and survival. Conclusion Mistletoes are heterogeneous group in the order Santalales which have versatile mechanisms for pollination, seed dispersal and nutrient acquisition from host plants. Infection by mistletoes triggers host plant responses, varying from mechanical to chemical mechanisms which are analogous to herbivory defences, and negatively impacts host plant growth and reproduction.
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    COVID-19 lockdown and natural resources: a global assessment on the challenges, opportunities, and the way forward
    (2022-01-29) Muche, Meseret; Yemata, Getahun; Molla, Eyayu; Muasya, A M; Tsegay, Berhanu A
    Background: The Coronavirus (COVID-19) is a global pandemic caused by SARS-CoV-2, which has an enormous effect on human lives and the global environment. This review aimed to assess the global scientific evidence on the impact of COVID-19 lockdown on natural resources using international databases and search engines. Thus, the unprecedented anthropause due to COVID-19 has positive and negative effects on natural resources. Main body This review showed that the unprecedented pandemic lockdown events brought a negative impact on the physical environment, including pollution associated with a drastic increase in person protective equipment, deforestation, illegal poaching and logging, overfishing, disruption of the conservation program and projects. It is noted that the spread of pandemic diseases could be aggravated by environmental pollution and a rapid increase in the global population. Despite these negative impacts of COVID-19, the anthropause appear to have also several positive effects on natural resources such as short term reduction of indoor and outdoor environmental pollutants (PM2.5, PM10, NO2, SO2, CO, and CO2), reduction in noise pollutions from ships, boats, vehicles, and planes which have positive effects on aquatic ecosystems, water quality, birds behaviour, wildlife biodiversity, and ecosystem restoration. Conclusion Therefore, governments and scientific communities across the globe have called for a green recovery to COVID-19 and implement multi-actor interventions and environmentally friendly technologies to improve and safeguard sustainable environmental and biodiversity management and halt the next pandemic.