Biology and resource acquisition of mistletoes, and the defense responses of host plants

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

Sorghum Landraces Production Practices in Nyanza, Coast and Eastern Regions, Kenya

Sorghum Sorghum bicolar L. is an important cereal crop grown in the semi-arid areas. It is rank as the fifth key cereal crop worldwide. The ability of sorghum to adapt to drought, salinity, infertile soils, and high temperatures makes it a critical crop in the dry regions. However, farmers grow many landraces some of which do not perform well since the majority cannot afford nitrogenous fertilizers to boost their harvest. Therefore, a baseline survey was conducted in Eastern, Nyanza and Coastal regions to assess the production systems for sorghum. Structured questionnaires were used to gather information from a total of 76 randomly selected farmers in the study regions. Data on socio-economic characteristics, sorghum varieties, use of farm inputs, and source of seeds, farming systems, traits preference, farm sizes, yields and constraints in production of the crop was collected. Parameters studied were analyzed using Statistical Programmes for Social Sciences (SPSS) (IBM SPSS Statistics 20). Results showed that majority of respondents in Eastern (99%), 80% in Nyanza and all respondents in the coastal region cultivated landraces. Most of the respondents had farm sizes between 0.5-5acres. A larger proportion of respondents in the three regions reported low harvests from their farms, recording below 5 bags every season. Most of the farmers across the three regions intercrop sorghum with other crops with all respondents in Eastern, 80% in Coast and 68% in Nyanza. Some farmers plant sorghum without fertilizers, others used either inorganic or organic fertilizers while the rest use both organic and inorganic. The traits desired by farmers in the region included high yields, early maturity, resistance to pest and diseases, sweetness and tolerance to drought. Farmers cited pests and diseases, weeds such as striga, and drought as the key constraints to sorghum production in the regions. Key words: drought, landraces, sorghum, tolerance, traits DOI: 10.7176/JESD/10-10-16 Publication date:May 31st 201

COVID-19 lockdown and natural resources: a global assessment on the challenges, opportunities, and the way forward

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

First molecular phylogenetic insights into the evolution of Eriocaulon (Eriocaulaceae, Poales)

Eriocaulon is a genus of c. 470 aquatic and wetland species of the monocot plant family Eriocaulaceae. It is widely distributed in Africa, Asia and America, with centres of species richness in the tropics. Most species of Eriocaulon grow in wetlands although some inhabit shallow rivers and streams with an apparent adaptive morphology of elongated submerged stems. In a previous molecular phylogenetic hypothesis, Eriocaulon was recovered as sister of the African endemic genus Mesanthemum. Several regional infrageneric classifications have been proposed for Eriocaulon. This study aims to critically assess the existing infrageneric classifications through phylogenetic reconstruction of infrageneric relationships, based on DNA sequence data of four chloroplast markers and one nuclear marker. There is little congruence between our molecular results and previous morphology-based infrageneric classifications. However, some similarities can be found, including Fyson’s sect. Leucantherae and Zhang’s sect. Apoda. Further phylogenetic studies, particularly focusing on less well sampled regions such as the Neotropics, will help provide a more global overview of the relationships in Eriocaulon and may enable suggesting the first global infrageneric classification

Biogeographical patterns of legume-nodulating <i>Burkholderia </i>spp.:from African Fynbos to continental scales

UNLABELLED: Rhizobia of the genus Burkholderia have large-scale distribution ranges and are usually associated with South African papilionoid and South American mimosoid legumes, yet little is known about their genetic structuring at either local or global geographic scales. To understand variation at different spatial scales, from individual legumes in the fynbos (South Africa) to a global context, we analyzed chromosomal (16S rRNA, recA) and symbiosis (nifH, nodA, nodC) gene sequences. We showed that the global diversity of nodulation genes is generally grouped according to the South African papilionoid or South American mimosoid subfamilies, whereas chromosomal sequence data were unrelated to biogeography. While nodulation genes are structured on a continental scale, a geographic or host-specific distribution pattern was not detected in the fynbos region. In host range experiments, symbiotic promiscuity of Burkholderia tuberum STM678(T) and B phymatum STM815(T) was discovered in selected fynbos species. Finally, a greenhouse experiment was undertaken to assess the ability of mimosoid (Mimosa pudica) and papilionoid (Dipogon lignosus, Indigofera filifolia, Macroptilium atropurpureum, and Podalyria calyptrata) species to nodulate in South African (fynbos) and Malawian (savanna) soils. While the Burkholderia-philous fynbos legumes (D lignosus, I filifolia, and P calyptrata) nodulated only in their native soils, the invasive neotropical species M pudica did not develop nodules in the African soils. The fynbos soil, notably rich in Burkholderia, seems to retain nodulation genes compatible with the local papilionoid legume flora but is incapable of nodulating mimosoid legumes that have their center of diversity in South America. IMPORTANCE: This study is the most comprehensive phylogenetic assessment of root-nodulating Burkholderia and investigated biogeographic and host-related patterns of the legume-rhizobial symbiosis in the South African fynbos biome, as well as at global scales, including native species from the South American Caatinga and Cerrado biomes. While a global investigation of the rhizobial diversity revealed distinct nodulation and nitrogen fixation genes among South African and South American legumes, regionally distributed species in the Cape region were unrelated to geographic and host factors.status: publishe

Modern cities modelled as “super-cells” rather than multicellular organisms: Implications for industry, goods and services

The structure and “metabolism” (movement and conversion of goods and energy) of urban areas has caused cities to be identified as “super-organisms”, placed between ecosystems and the biosphere, in the hierarchy of living systems. Yet most such analogies are weak, and render the super-organism model ineffective for sustainable development of cities. Via a cluster analysis of 15 shared traits of the hierarchical living system, we found that industrialized cities are more similar to eukaryotic cells than to multicellular organisms; enclosed systems, such as factories and greenhouses, paralleling organelles in eukaryotic cells. We further developed a “super-cell” industrialized city model: a “eukarcity” with citynucleus (urban area) as a regulating centre, and organaras (enclosed systems, which provide the majority of goods and services) as the functional components, and cityplasm (natural ecosystems and farmlands) as the matrix. This model may improve the vitality and sustainability of cities through planning and management