Impact of Ageratum conyzoides L. on the diversity and composition of vegetation in the Shivalik hills of Himachal Pradesh (Northwestern Himalaya), India

The flora of the Shivalik hills of Himachal Pradesh, India is under threat due to the rapid invasion of invasive species. Invasive species means an alien species, which becomes established in natural or semi-natural ecosystems and threatens native biological diversity. In their new regimes they show diverse life forms, habit, morphology, reproductive biology, grow fast, have the ability to grow under different habitats, produce enormous number of very small, light weight seeds that and can-survive in soil for years helping long distance dispersal and spread. They can out-compete native species, reduce wildlife habitat potential, alter natural ecosystem processes and limit overall biodiversity. Ageratum conyzoides is one such widely adaptive weed from sub-tropical America that has entered in the Shivalik hills of Hamrpur district of Himachal Pradesh. It has grown as monocultures, in grasslands, forests, agricultural, plantations and horticultural fields in Himachal Pradesh. Hence, it was decided to evaluate the impact of A. conyzoides on the diversity and floristic compositions of native species. It was found that as compared to control, in the Ageratum invaded area; the average number of plant species has reduced by 32.10%; the α diversity has reduced by 41.21% and the dry biomass of plants has also reduced significantly. It was concluded that invasion of A. conyzoides is drastically affecting the productivity and diversity of the invaded areas in Shivalik hills of Hamirpur district

ALLELOPATHIC IMPACT OF ESSENTIAL OIL OF TAGETES MINUTA ON COMMON AGRICULTURAL AND WASTELAND WEEDS

ABSTRACTObjective: Tagetes minuta (Family Asteraceae) is an aromatic plant possessing volatile essential oil.  Its oil finds extensive use in flavor and perfume industry. T. minuta oil also possess medicinal and insecticidal properties as antiheminthic, nematicidal, bactericidal, antiviral, fngicidal and insecticidal. The plant has been explored for herbicidal potential in very few reports. The aim of present study is to find out its allelopathic potential against common wasteland and agricultural weeds.Material & Methods: Various agricultural and wasteland weeds were selected for laboratory growth studies. Oil was applied in solution form using an emulsifier.Results: Growth of all test weeds was inhibited by T. minuta oil; however, effect was maximum in Amaranthus tricolor with complete inhibition at 1µl/ml and E. cruss-galli was least affected with complete inhibition at 5µl/ml concentration of T. minuta oil.Conclusion: T. minuta oil offers great potential for effective weed management in agricultural as well as wasteland areas. Keyowrds: Tagetes minuta, essential oil, allelopathy, solution form, wasteland, agricultural, weed

Chemical composition and inhibitory activity of essential oil from decaying leaves of Eucalyptus citriodora

A study was undertaken to explore the content and composition of volatile oil from decaying leaves of lemon-scented eucalypt (Eucalyptus citriodora Hook.) not analyzed earlier. GC and GC-MS analysis of the oil (yield 0.6%) revealed the monoterpenoid nature with citronellal (52.2%), citronellol (12.3%) and isoisopulegol (11.9%) as the major constituents. Overall, 17 components were identified that accounted for over 94% of the decaying leaf oil. Surprisingly, the decaying leaf oil contained nearly 1.8% of trans-rose oxide, which is generally absent in eucalypt essential oil. Decaying leaf oil and its major 2 components (citronellal and citronellol) inhibited the germination and root elongation of two weeds Ð Cassia occidentalis (broad-leaved) and Echinochloa crus-galli (grassy weed). Based on the dose-response studies, I 50 values were determined for decaying leaf oil and the effect was more on germination only of broad-leaved weed (C. occidentalis), whereas that of citronellal and citronellol were on germination as well as root length of E. crus-galli (grassy weed). Based on I 50 values it was observed that citronellal was more phytotoxic and germination inhibiting in nature, whereas citronellol was a more potent root inhibitor, thereby indicating a possible different mode of action. The study concludes that decaying leaf oil hold a good commercial value for exploitation as weed management agent

Factors associated with stigma and manifestations experienced by Indian health care workers involved in COVID-19 management in India: A qualitative study

Healthcare personnel who deal with COVID-19 experience stigma. There is a lack of national-level representative qualitative data to study COVID-19-related stigma among healthcare workers in India. The present study explores factors associated with stigma and manifestations experienced by Indian healthcare workers involved in COVID-19 management. We conducted in-depth interviews across 10 centres in India, which were analysed using NVivo software version 12. Thematic and sentiment analysis was performed to gain deep insights into the complex phenomenon by categorising the qualitative data into meaningful and related categories. Healthcare workers (HCW) usually addressed the stigma they encountered when doing their COVID duties under the superordinate theme of stigma. Among them, 77.42% said they had been stigmatised in some way. Analyses revealed seven interrelated themes surrounding stigma among healthcare workers. It can be seen that the majority of the stigma and coping sentiments fall into the mixed category, followed by the negative sentiment category. This study contributes to our understanding of stigma and discrimination in low- and middle-income settings. Our data show that the emergence of fear of the virus has quickly turned into a stigma against healthcare workers

Allelopathic effect of two volatile monoterpenes against bill goat weed (Ageratum conyzoides L.)

A study was conducted to assess the allelopathic effect of two volatile monoterpenes viz. cineole and citronellol on Ageratum conyzoides with a view to explore the possibility of their exploitation for future weed management. Both the monoterpenes severely affected the germination, speed of germination, seedling growth, chlorophyll content and respiratory activity. After two weeks of exposure, the weed plants wilted. Out of the two monoterpenes, cineole was more toxic in causing injury to the weed

Phenolic allelochemicals released by Chenopodium murale affect the growth, nodulation and macromolecule content in chickpea and pea

The present study was conducted to investigate the effect of the residue of Chenopodium murale L. on growth, nodulation and macromolecule content of two legume crops, viz., Cicer arietinum L. (chickpea) and Pisum sativum L. (pea). A significant reduction in root and shoot length as well as dry matter accumulation occurred when both the legumes were grown in the soil amended with 5, 10, 20 and 40 g residue kg<SUP>-1</SUP>soil. In general, a gradual decline in growth was associated with an increasing amount of residues in the soil. There was also a significant reduction in total chlorophyll content and the amounts of protein and carbohydrates (macromolecules) in plants growing in the residue-amended soil. The nodulation was completely absent in chickpea and pea when the plants were grown in the soil amended with 10 and 20 g residue kg<SUP>-1</SUP> soil, respectively. At a lower rate of residue amendment (5 g kg<SUP>-1</SUP> soil), a significant decline in nodule number and weight, and leghaemoglobin content was recorded. Root oxidizability, an indirect measure of tissue viability and cellular respiration, was adversely affected in both the legumes under various treatments of residue amendment. The observed growth reduction concomitant with increased proline accumulation indicated the presence of some inhibitory compounds in the residue-amended soil. It was rich in phenolics identified as protocatechuic, ferulic, p-coumaric and syringic acid with 12.8, 30.4, 20.2 and 33.6% relative content, respectively. The results suggest that the residue of C. murale releases phenolic allelochemicals, which deleteriously affect the growth, nodulation and macromolecule content of chickpea and pea

Status, invasiveness and environmental threats of three tropical American invasive weeds (Parthenium hysterophorus L., Ageratum conyzoides L., Lantana camara L.) in India

Invasive weeds have threatened the integrity of ecosystems throughout the world. They affect not only the species diversity of native areas but also their biological integrity. In India, a number of invasive exotic weeds have been reported but some viz. Parthenium hysterophorus, Lantana camara and Ageratum conyzoides, especially those from tropical America are troublesome and have caused adverse ecological, economic and social impact. These weeds can be seen growing in different landscapes but are luxuriantly localized in unattended forests and cultivated areas. Parthenium hysterophorus (Asteraceae, commonly known as congress grass) is perhaps the most troublesome and noxious weed of urban and rural India. Besides rapidly colonizing areas replacing the native vegetation, it is also known to cause a number of human health problems such as skin allergy, rhinitis and irritation to eyes of the residents in the vicinity. Likewise, it causes fodder scarcity in addition to being unpalatable and toxic to livestock. Lantana camara (Verbenaceae), another serious tropical American pest, has encroached upon large areas of land, especially the forests where it has virtually replaced the forest floor vegetation and reduced tree growth. Also because of its bushy and spreading type of growth it obstructs forest operations. The third weed, Ageratum conyzoides (Asteraceae, Billy goat weed) has invaded agricultural fields. It interferes with crops and causes yield reductions of major staple crops of India. When it invades rangeland areas, it out competes native grasses causing scarcity of fodder. These weeds have similar growth strategies such as fast growth rates, short life-cycles, greater reproductive potential, high competitive abilities and allelopathy that make them successful invaders of native habitats. Mechanical, chemical, biological and cultural control tactics have failed individually, though integrated approaches combining all these approaches along with community participation and proper land management have been relatively successful. This paper presents various aspects of biology, ecology, hazards and control measures of these weeds

Phytotoxicity of Ageratum conyzoides residues towards growth and nodulation of Cicer arietinum

A study was conducted to find out the phytotoxic effect of invasive weed Ageratum conyzoides on chickpea (Cicer arietinum). Weed residues amended in the soil significantly reduced the chickpea growth. Root length, plant height and biomass of chickpea were lower in the soils amended with below- or above-ground weed residues. In addition, compared to control, the nodulation (nodule number, their weight and leghemoglobin content) of chickpea was also reduced in the amended soils. The observed reduction in chickpea growth and nodulation was attributed to the presence of phytotoxic phenolics in the residues

Assessment of allelopathic interference of Chenopodium album through its leachates, debris extracts, rhizosphere and amended soil

A study conducted to assess the allelopathic interference of invasive weed Chenopodium album indicated that aqueous leachates of C. album plant parts (roots, whole plant, and leaves), debris extracts and rhizosphere soil deleteriously affected the germination and initial growth of two test plants - Cassia occidentalis (a weed) and Phaseolus aureus (a crop). Further, the plant growth in terms of height, biomass, chlorophyll and protein content was significantly lesser in soil amended with C. album debris. Aqueous leachates, debris extracts, rhizosphere soil and debris amended soil were found to contain significantly higher amounts of water-soluble phenolics - the known phytotoxins. These phytotoxins in root, above-ground parts and leaves were phenolic acids, namely gallic, chlorogenic, caffeic, vanillic, p-coumaric, syringic and ferulic. Among these, chlorogenic acid was present in the maximum amount in the leaves and roots. The study concludes that C. album releases phenolics into the soil and these are probably involved in the growth inhibitory effect of C. album

Potential utilization of dried powder of Tagetes minuta as a natural herbicide for managing rice weeds

Tagetes minuta is an aromatic essential plant with wide range of biological activity including medicinal properties. A study was undertaken to explore the potential herbicidal activity of Tagetes minuta leaf powder (at 1, 2, and 4 t ha-1) towards two invasive weeds-Echinochloa crus-galli and Cyperus rotundus-of rice fields. It was observed that T. minuta leaf powder applied to rice field soil significantly reduced emergence and growth of both the weed species in pots under greenhouse and in rice field plots. At 1 and 2 t ha-1 dose of application, emergence and growth of weeds was severally affected, whereas there was no effect on the growth and yield attributes of rice. Rather, at this dose of application yield of rice increased significantly and the effect was similar to that observed with the herbicidal application under field conditions. Based on the study, it could be concluded that T. minuta possesses weed-suppressing ability and could be used as a natural herbicide