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Seed germination ecology of Ageratum houstonianum: A major invasive weed in Nepal.

ABSTRACT: In recent years, spread of invasive alien plant species (IAPS) has been a major concern in Nepal. One such IAPS is Ageratum houstonianum, an Asteraceae, that is a prolific seed producer and difficult-to-control in farmland and various ecological regions causing crop yield and biodiversity losses. However, very little information is available on the germination biology and ecology of this species. Therefore, experiments were conducted to assess the effect of water stress, pH level, and light requirement on seed germination, and the effect of seed burial depth on seedling emergence. Water stress was simulated by polyethylene glycol solutions ranging from 0-5.56 MPa and pH solutions ranging from 4 to 9 were prepared using hydrochloric acid and sodium hydroxide. Germination tests were conducted in petri dishes lined with filter paper and placed in a controlled environment chamber set at 20° C. Light requirement comparisons were made by having petri dishes wrapped with aluminum foil or left unwrapped. Seedling emergence was evaluated by placing seeds at depths ranging from 0 to 20 mm in the soil. Results indicated that this species was moderately drought-tolerant because germination ceased beyond 0.51 MPa. Greater germination occurred at neutral to acidic than at alkaline pH levels. The seeds were positively photoblastic because no germination occurred under dark condition. No seedlings emerged from seeds placed more than 2 mm deep in the soil, indicating that this is a primarily surface germinating species. These findings will help predict future invasions and in development of management strategies for this IAPS.

SUBMITTER: Lamsal A

PROVIDER: S-EPMC6874205 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Seed germination ecology of Ageratum houstonianum: A major invasive weed in Nepal.

Lamsal Anju A Devkota Mohan P MP Shrestha Deepa S DS Joshi Srijana S Shrestha Anil A

PloS one 20191121 11

In recent years, spread of invasive alien plant species (IAPS) has been a major concern in Nepal. One such IAPS is Ageratum houstonianum, an Asteraceae, that is a prolific seed producer and difficult-to-control in farmland and various ecological regions causing crop yield and biodiversity losses. However, very little information is available on the germination biology and ecology of this species. Therefore, experiments were conducted to assess the effect of water stress, pH level, and light requ ...[more]

PMID: 31751412

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Project description:Mosquitoes are unquestionably the most medic arthropod vectors of disease. Culex pipiens, usually defined as a common house mosquito, is a well-known carrier of several virus diseases. Crude ethanol extracts of different organs of Agratum houstonianum are tested with Culex pipiens Linnaeus (Diptera: Culicidae) to determine their larvicidal, antifeedant, and repellency effects. Alongside biochemical analysis, the activity of the AChE, ATPase, CarE, and CYP-450 is detected in the total hemolymph of the C. pipiens larvae to examine the enzymatic action on the way to explain their neurotoxic effect and mode of action. Through HPLC and GC-MS analysis of the phytochemical profile of A. houstonianum aerial parts is identified. The larvicidal activity of aerial parts; flower (AF), leaf (AL), and stem (AS) of A. houstonianum extracts are evaluated against the 3rd instar larvae of C. pipiens at 24-, 48- and 72-post-treatment. A. houstonianium AF, AL, and AS extracts influenced the mortality of larvae with LC50 values 259.79, 266.85, and 306.86 ppm, respectively after 24 h of application. The potency of AF and AL extracts was 1.69- and 1.25-folds than that of AS extract, respectively. A high repellency percentage was obtained by AF extract 89.10% at a dose of 3.60 mg/cm2. A. houstonianium AF prevailed inhibition on acetylcholinesterase and decrease in carboxylesterase activity. Moreover, a significant increase in the ATPase levels and a decrease in cytochrome P-450 monooxegenase activity (- 36.60%) are detected. HPLC analysis prevailed chlorogenic and rosmarinic acid as the major phenolic acids in AL and AF, respectively. GC-MS analysis of A. houstonianum results in the identification of phytol as the major makeup. Precocene I and II were detected in AF. Linoleic, linolenic, and oleic acid were detected in comparable amounts in the studied organs. Overall, results suggest that the A. houstonianum flower extract (AF) exhibits significant repellent, antifeedant, and larvicidal activities.

Project description:IntroductionParthenium hysterophorus (Asteraceae) is an invasive weed species that has invaded over 50 countries worldwide. It was first detected in 1980 at Tirat-Zvi, in eastern-northern Israel. In recent years, there has been an increasing concern over the spread of this weed in agricultural and non-agricultural habitats across the country. However, very little is known about the biology of P. hysterophorus and its variation among populations.MethodsSeeds collected from five locations across Israel were germinated and plants were grown in pollen-proof cages under uniform conditions to produce the progeny populations. Spatial parameters, weight and germination under different environmental conditions were recorded for field and progeny populations.ResultsSeeds originating from field populations were significantly smaller and lighter than seeds of the progeny populations. Germination occurred in the range of 10°C to 30°C (To ranges from 19°C to 22.3°C, Tb ranged from 9°C to 15°C, Tc ranged from 24 ℃ to 30.5°C), depending on generation and population. A water potential-based model was developed to estimate germination under different soil water content using specific parameters (b - slope, d - upper limit, e - infliction point). The model suggests a correlation between germination and water potential. Indeed, reduced germination was recorded for the lower water potentials especially for the progeny populations. Spatial parameters, weight and germination under different environmental conditions were recorded for field and progeny populations.DiscussionWe identified differences in seed size and weight, germination under different temperatures, and osmotic potential among P. hysterophorus Israeli populations. Differences across generations may arise due to the transgenerational effects. Our results, may shed light on the germination abilities of P. hysterophorus populations and provide vital insight into understanding the invasive capabilities of this highly noxious weed.

Project description:Background and aimsInternal seed morphological traits such as embryo characteristics and nutritive tissue can vary considerably within a plant lineage. These traits play a prominent role in germination processes and the success of seedling establishment, and are therefore under high selective pressure, especially in environments hostile to seedlings, such as arid, saline or highly dynamic habitats. We investigated the relationships of seed internal morphology and germination characteristics of 84 species of Amaranthaceae s.l., a family with numerous lineages that have adapted to stressful growing conditions.MethodsWe used seed cross-sections to assess embryo type and the ratios of embryo to seed surface and radicle to cotyledon length. Furthermore, seed mass, mean time to germination, habitat preferences and further plant traits such as C3 or C4 photosynthesis and life form were compiled for each species. Data were analysed using phylogenetic comparative methods.Key resultsWe found embryo type (λ = 1), log seed mass (λ = 0.86) and the ratio of embryo to seed size (λ = 0.78) to be evolutionarily stable, with an annular embryo as ancestral in the family. Linked to shifts to the three derived embryos types (spiral, horseshoe-shaped and curved) is an increase in the ratio of root to cotyledon length and a reduction of nutritive tissue. We observed stabilizing selection towards seeds with relatively large embryos with longer radicles and less nutritive tissue that are able to germinate faster, especially in lineages with C4 photosynthesis and/or salt tolerance.ConclusionsWe conclude that the evolutionary shift of nutrient storage from perisperm to embryo provides an ecological advantage in extreme environments, because it enables faster germination and seedling establishment. Furthermore, the evolutionary shift towards a higher ratio of root to cotyledon length especially in small-seeded Amaranthaceae growing in saline habitats can provide an ecological advantage for fast seedling establishment.

Project description:Conyza sumatrensis (Retz.) E. H. Walker is an obnoxious weed, emerging as an invasive species globally. Seed germination biology of four populations of the species stemming from arid, semi-arid, temperate, and humid regions was determined in this study. Seed germination was recorded under six different environmental cues (i.e., light/dark periods, constant and alternating day and night temperatures, pH, salinity, and osmotic potential levels) in separate experiment for each cue. Populations were main factor, whereas levels of each environmental cue were considered as sub-factor. The impact of seed burial depths on seedling emergence was inferred in a greenhouse pot experiment. Seed germination was recorded daily and four germination indices, i.e., seed germination percentage, mean germination time, time to reach 50% germination, and mean daily germination were computed. Tested populations and levels of different environmental cues had significant impact on various seed germination indices. Overall, seeds stemming from arid and semi-arid regions had higher seed germination potential under stressful and benign environmental conditions compared to temperate and humid populations. Seed of all populations required a definite light period for germination and 12 hours alternating light and dark period resulted in the highest seed germination. Seed germination of all populations occurred under 5-30°C constant and all tested alternate day and night temperatures. However, the highest seed germination was recorded under 20°C. Seeds of arid and semi-arid populations exhibited higher germination under increased temperature, salinity and osmotic potential levels indicating that maternal environment strongly affected germination traits of the tested populations. The highest seed germination of the tested populations was noted under neutral pH, while higher and lower pH than neutral had negative impact on seed germination. Arid and semi-arid populations exhibited higher seed germination under increased pH compared to temperate and humid populations. Seed burial depth had a significant effect on the seedling emergence of all tested populations. An initial increase was noted in seedling emergence percentage with increasing soil depth. However, a steep decline was recorded after 2 cm seed burial depth. These results indicate that maternal environment strongly mediates germination traits of different populations. Lower emergence from >4 cm seed burial depth warrants that deep burial of seeds and subsequent zero or minimum soil disturbance could aid the management of the species in agricultural habitats. However, management strategies should be developed for other habitats to halt the spread of the species.

Dataset Information

Seed germination ecology of Ageratum houstonianum: A major invasive weed in Nepal.

Publications

Seed germination ecology of Ageratum houstonianum: A major invasive weed in Nepal.

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