Muhammad Mansoor Javaid

Influence of seed size and ecological factors on the germination and emergence of field bindweed (Convolvulus arvensis)

An understanding of seed germination ecology of weeds can assist in predicting their potential distribution and developing effective management strategies. Influence of environmental factors and seed size on germination and seedling emergence of Convolvulus arvensis (field bindweed) was studied in laboratory and greenhouse conditions. Germination occurred over a wide range of constant temperatures, between 15 and 40 oC, with optimum germination between 20 and 25 oC. Time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased with an increase in temperature from 20 oC, salinity and osmotic stress. However, germination was tolerant to low salt (25 mM) or osmotic stress (0.2 MPa), but as salinity and osmotic stress increased, germination percentage and germination index decreased. Seeds of C. arvensis placed at soil surface showed maximum emergence and decreased as seeding depth increased. Seeds of C. arvensis germinated over a wide range of pH (4 to 9) but optimum germination occurred at pH 6 to 8. Under highly alkaline and acidic pH, time to start germination, time to 50% germination and mean germination time increased while germination percentage and germination index decreased. Increase in field capacity caused decreased time to start germination, time to 50% germination and mean germination time but increased germination percentage and germination index. Bigger seeds had low time to start germination, time to 50% germination and mean germination time but high germination percentage and germination index. Smaller seeds were more sensitive to environmental factors as compared to larger or medium seeds. It can be concluded that except for pH, all environmental factors and seed sizes adversely affect C. arvensis as regards seed germination or emergence and germination or emergence traits, and larger seeds result in improved stand establishment and faster germination than small seeds, regardless of moisture stress or deeper seeding depth.

Tritrophic interactions between parasitoids and cereal aphids are mediated by nitrogen fertilizer

Host plant nutritional quality can directly and indirectly affect the third trophic levels. The aphid–parasitoid relationship provides an ideal system to investigate tritrophic interactions (as the parasitoids are completely dependent for their development upon their hosts) and assess the bottom up forces operating at different concentrations of nitrogen applications. The effects of varying nitrogen fertilizer on the performance of Aphidius colemani (V.) reared on Sitobion avenae (F.) and Aphidius rhopalosiphi (D.) reared on Rhopalosiphum padi (L.) were measured. Parasitism and percent emergence of parasitoids were positively affected by nitrogen fertilizer treatments while developmental duration (egg, larval, and pupal stages) was not affected by increasing nitrogen inputs. In males and females of both parasitoid species, adult longevity increased with the increasing nitrogen fertilizer. Hind tibia length and mummy weight of both parasitoid species increased with nitrogen fertilizer concentrations, as a result of larger aphids. This study showed that nitrogen application to the soil can have important consequences for aboveground multitrophic interactions.

Optimization of Application Efficacy for POST Herbicides with Adjuvants on Three-Cornered Jack (Emex australis Steinheil) in Wheat

Abstract Field studies were conducted to evaluate POST herbicides with adjuvants for the control of three-cornered jack in winter wheat. The herbicides evaluated were fluroxypyr 9.7% w/w + MCPA 38.8% w/w (formulated mixture [450 g ai ha−1]), carfentrazone-ethyl (20 g ai ha−1), bromoxynil 26.8% w/w + MCPA 40.0% w/w (formulated mixture [450 g ai ha−1]), thifensulfuron-methyl (75 g ai ha−1), and tribenuron-methyl (75 g ai ha−1), applied alone or tank mixed with the adjuvants alkyl ether sulfate sodium salt (625 mL ha−1) or fatty alcohol ethoxylate (375 mL ha−1). The addition of adjuvants to carfentrazone-ethyl resulted in > 94% control of three-cornered jack. Both adjuvants enhanced the efficacy of all herbicides for control of three-cornered jack, except thifensulfuron-methyl. However, a maximum increase in phytotoxicity on three-cornered jack was achieved with the addition of either adjuvant to tribenuron-methyl compared with herbicides used alone. Bromoxynil + MCPA and carfentrazone-ethyl gave maximum wheat yield and yield components. Nomenclature: Fluroxypyr + MCPA; carfentrazone-ethyl; bromoxynil + MCPA; thifensulfuron-methyl; tribenuron-methyl; three-cornered jack, Emex australis Steinheil; wheat, Triticum aestivum L. Resumen Se realizaron estudios de campo para evaluar herbicidas POST con adyuvantes para el control de Emex australis en trigo de invierno. Los herbicidas evaluados fueron fluroxypyr 9.7% w/w + MCPA 38.8% w/w (mezcla en formulación [450 g ai ha−1]), carfentrazone-ethyl (20 g ai ha−1), bromoxynil 26.8% w/w + MCPA 40.0% w/w (mezcla en formulación [450 g ai ha−1]), thifensulfuron-methyl (75 g ai ha−1), y tribenuron-methyl (75 g ai ha−1), aplicados solos o en mezcla en tanque con los adyuvantes sal de alkyl ether sulfate sodium (625 mL ha−1) o alcohol graso ethoxylate (375 mL ha−1). La adición de adyuvantes a carfentrazone-ethyl resultó en >94% de control de E. australis. Ambos adyuvantes mejoraron la eficacia de todos los herbicidas para el control de E. australis, excepto thifensulfuron-methyl. Sin embargo, un incremento máximo de fitotoxicidad en E. australis se alcanzó con la adición de cualquiera de los adyuvantes a tribenuron-methyl al compararse con los herbicidas usados solos. Bromoxynil + MCPA y carfentrazone-ethyl brindaron el mayor rendimiento y componentes de rendimiento del trigo.

Germination ecology of Rhynchosia capitata: an emerging summer weed in Asia

Rhynchosia capitata is becoming an increasing problem in summer crops, such as cotton, soybean, pearl millet and mungbean in many Asian countries. Laboratory and greenhouse studies have been conducted to determine the effects of several environmental factors on seed germination patterns and seedling emergence of R. capitata. We investigated whether the diverse ecological factors such as temperature, light, salinity, moisture stress, pH, and soil depth affected germination and seedling emergence of R. capitata. Germination increased as temperature increased from 25 oC and significantly reduced at 45 oC. Presence or absence of light did not influence germination. Germination of R. capitata was sensitive to increased salt and moisture stress, as well as to seed burial depth. Only 48% of seeds germinated at 150 mM salt concentration compared to 100% in control (distilled water). Similarly, 15% of seeds germinated at an osmotic potential of ‑0.8 MPa compared to 88% at ‑0.2 MPa. The optimum pH for seed germination of R. capitata was 7 (98% germination), but the seeds also germinated at lower level of pH 5 (85%) and at higher level of pH 10 (75%). In seed burial trial, maximum seedling emergence of 93% occurred at 2 cm depth, and seedling did not emerge from a depth of 12 cm. The high germination ability of R. capitata under a wide range of ecological factors suggests that this species is likely to be the one to cause more problems in a near future, if not managed appropriately.

Yield Losses in Chickpea with Varying Densities of Dragon Spurge (Euphorbia dracunculoides)

Abstract Knowledge of economic threshold level and growth habits of weeds in chickpea is essential to implement timely, effective, and economical weed control treatments. The effect of weed density on growth and yield performance in chickpea using dragon spurge as a test weed was investigated for 2 consecutive yr. Dragon spurge density levels of 5, 10, 15, 20, 25, 30, 35, and 40 plants m−2 were compared with weed-free plots. Each increment in densities of dragon spurge from 5 to 40 plants m−2 reduced plant height, number of fruits, seeds, and dry weight per plant. Chickpea grain yield losses varied between 1 to 63% with dragon spurge density ranging from 5 to 40 plants m−2. The seed protein content of chickpea was found to be significantly reduced above a weed density of 25 plants m−2. Maximum N, P and K uptake by dragon spurge was 1,520, 1,020, and 7,350 mg m−2, respectively. Thus, dragon spurge should be controlled at densities above 5 plants m−2 to achieve optimum chickpea yield. Nomenclature: Chickpea, Cicer arietinum L.; Euphorbia dracunculoides Lam.

Allelopathic effects of Rhynchosia capitata on germination and seedling growth of mungbean

Experiments were conducted to evaluate the allelopathic influence of Rhynchosia capitata on germination and seedling growth of mungbean (Vigna radiate) along with identification of the phytotoxic substances responsible for this activity. Water extracts of root, shoot, leaf, fruit and whole plant were prepared by soaking them in water in a ratio of 1:20 (w/v) for 24 h. All the extracts affected germination and seedling growth of mungbean, but higher inhibition was seen with R. capitata leaf water extracts. A linear decrease in the germination characteristics of mungbean was observed with the decrease in the concentration of leaf extract from 5% to 1%. The soil-incorporated residues (1-4% w/w) of R. capitata stimulated the growth of root and hypocotyl at low concentrations, while it inhibited their growth at higher concentrations. Rhynchosia capitata soil-incorporated residues (4% w/w) significantly reduced the seedling vigour index of mungbean in addition to their significant effect on total germination. A significant amount of water-soluble phenolic acids were found in R. capitata plant extracts. The content of total phenolic acids was higher in the leaf extract compared to that of the stem, fruit or root extracts. Two phenolic acids including vanillic acid and 4‑(hydroxymethyl) benzoic acid were found in R. capitata leaf extracts.

Optimizing activity of herbicides at reduced rate on Emex spinosa campd. with adjuvants

In pot experiments, two adjuvants were evaluated for their efficacy in enhancing activity of five herbicides applied at reduced rates (75% of the recommended rates) on Emex spinosa at the cotyledon-leaf and at the two- to four- leaf stage. Herbicides (at recommended rates) including fluroxypyr+MCPA at 450 g a.i. ha-1, carfentrazone-ethyl at 20 g a.i. ha-1, bromoxynil+MCPA at 450 g a.i. ha-1, thifensulfuron-methyl at 75 g a.i. ha-1 and tribenuronmethyl at 75 g a.i. ha-1 alone and tank mixed at reduced rates with adjuvants, namely, alkyl ether sulphate sodium salt at 625 mL ha-1 or fatty alcohol ethoxylate at 375 mL ha-1. Addition of the adjuvants to reduced rates of fluroxypyr+MCPA and carfentrazone-ethyl, increased their efficacy with 100% mortality and biomass reduction of E. spinosa at the cotyledon- leaf stage and at the two- to four- leaf stage which was similar to their recommended rates without the adjuvants except for carfentrazone-ethyl at a reduced rate without adjuvants at the two- to four- leaf stage. Bromoxynil+MCPA at reduced rates with alkyl ether sulphate sodium salt also gave 100% control of E. spinosa over weedy check at the two- to four- leaf stage. Both the adjuvants generally increased the efficacy of tribenuron-methyl at reduced rates when sprayed at both leaf stages. These findings suggest that the use of adjuvants may increase the efficacy of the above mentioned herbicides against E. spinosa and it may be incorporated in an integrated weed management program.

Effect of ecological factors on germination of horse purslane (Trianthema portulacastrum)

Trianthema portulacastrum e uma planta daninha bastante problematica para safras de verao, e observa-se a perda total de safras por causa da alta densidade desta planta daninha. Em experimentos de laboratorio, foi investigado o efeito de diferentes fatores ecologicos sobre a germinacao de sementes de T. portulacastrum coletadas em dois anos diferentes (2009 e 2005). O aumento da temperatura de 25 para 35 oC elevou a percentagem de germinacao de T. portulacastrum de 65 para 85%, a qual, em seguida, foi reduzi da para 71,25% a temperatura de 45 oC. A maxima germinacao de Trianthema portulacastrum ocorreu com agua destilada, em comparacao com solucoes salinas e niveis de estresse hidrico diferentes. A germinacao foi significativamente minima com niveis de estresse salino e hidrico de 250 mM e -0,8 MPa, respectivamente. A emergencia maxima (86,25%) ocorreu a 100% do nivel de capacidade de campo, mas diminuiu drasticamente a medida que a capacidade de campo foi reduzida, e a emergencia minima (30%) foi registrada no nivel de 25% da capacidade de campo. A menor germinacao de T. portulacastrum foi observada com pH 5, e o aumento no pH resultou em uma maior taxa de germinacao. A germinacao teve indices estatisticos semelhantes quando o pH variou entre 8 e 10. A profundidade da semeadura de 6 cm reduziu a emergencia de T. portulacastrum a zero. Foi observada a reducao da emergencia com o aumento da profundidade de zero para 5 cm. A emergencia maxima foi registrada a partir da superficie do solo (0 cm). O aumento de temperatura, salinidade, estresse hidrico, profundidade de semeadura (ate 4 cm) e a diminuicao da capacidade de campo aumentaram o tempo para iniciar a germinacao/emergencia, o tempo de 50% de germinacao/emergencia e tempo medio de germinacao/emergencia , mas o indice de germinacao/emergencia foi reduzido. As sementes coletadas em 2009 resultaram em maior germinacao do que as sementes antigas, colhidas em 2005. O conhecimento destas informacoes pode ajudar no desenvolvimento de um controle eficaz de T. portulacastrum.

Effect of Environmental Factors on Germination of Salsola foetida: Potential Species for Rehabilitation of Degraded Rangelands

ABSTRACT Information relating to germination and seedling emergence of a plant aids in determining the species potential distribution and also helps in designing appropriate plant management strategies within an agroecosystem. Salsola foetida Del. ex Spreng, a naturally occurring perennial shrub, is traditionally used as a medicinal plant and a promising camel fodder in the hypersaline, semiarid, and arid areas across the globe. A series of laboratory and greenhouse experiments were conducted to determine the effect of various environmental factors such as temperature, light, salinity, osmotic stress, pH, and seed burial depth on seed germination and seedling emergence of S. foetida. A decline in germination was observed with increases in temperature. The maximum germination of 95% was observed at 25/15°C followed by 83% at 30/20°C; however, minimum germination (35%) was observed at 40/30°C. Maximum seed germination (95%) was observed under 24-h darkness while a decrease in germination (72%) was recorded when seeds were kept in 24-h light. Under saline conditions, 67% of seeds germinated at 100 mM sodium chloride (NaCl) and germination decreased to 12% with an increase in salinity to 500 mM NaCl. The optimum pH for seed germination of S. foetida was 7 (97% germination), although 36% and 75% of seeds germinated at the pH levels of 5 and 10, respectively. About 5% of seeds germinated at an osmotic potential of — 0.8 MPa compared with 40% at — 0.2 MPa. However, seeds of S. foetida were found sensitive to increased burial depth. The maximum germination was observed at the soil surface, and emergence inhibited completely from the seeds buried at the 5-cm depth. The high germination ability of S. foetida over a wide range of environmental factors suggests that this species is likely to thrive easily under harsh arid conditions. Therefore, it is used as a potential candidate for the rehabilitation of rangelands and will be helpful in mitigating the adverse effect of climatic changes on humans and livestock in the degraded areas.

Foliar treatment with Lolium perenne (Poaceae) leaf extract alleviates salinity and nickel-induced growth inhibition in pea

Abstract The plants of pea (Pisum sativum L.) were grown under NaCl and/or NiCl2 stress, to comparatively evaluate stress-mitigating effects of pure proline and naturally proline-enriched Lolium perenne (L.) aqueous leaf extract. Both stress factors (salinity and nickel) significantly reduced plant biomass, chlorophyll content, photosynthetic activity, stomatal conductance, intercellular carbon dioxide (CO2) level, number of stomata, stomatal size, water-use efficiency, relative water content (RWC), and the membrane stability index (MSI). However, the proline and glycinebetaine contents, lipid peroxidation, electrolyte leakage, and activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, guaiacol peroxidase, and glutathione reductase) were significantly increased. Exogenously applied proline and Lolium perenne (LP) leaf extracts significantly overcame the nickel and/or salinity-induced toxic effects on growth, RWC, and various photosynthetic attributes. However, follow-up treatment with proline and LP-leaf-extract detoxified the stress caused by NiCl2 and/or NaCl, by suppressing lipid peroxidation and electrolyte leakage, accelerating the antioxidant enzyme activities, and improving the MSI, leaf/root proline, and glycinebetaine contents. LP-leaf-extract proved to be better than pure proline for improving growth, gas exchange parameters, osmolytes, RWC, and antioxidant enzyme activities. As LP-leaf-extract was enriched with a substantial amount of proline along with many other essential osmoprotectants, it was found to be as effective as pure proline in ameliorating growth, some major physiological attributes, and non-enzymatic and enzymatic antioxidant activities in the pea, under nickel and/or salinity stress. Thus, it could be used as an alternative inexpensive source of proline, to be used as a mitigating agent for protecting plants against the deleterious effects of nickel and/or salinity stress.