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Emex spinosa and Emex australis are invasive dicotyledonous weeds. The effects of various environmental factors on the germination of these weeds were investigated under laboratory and glasshouse conditions. Germination response of both species was lower at warmer temperature, and maximum germination was recorded at 20/12°C (day/night). Light stimulated germination in both species, but considerable germination also occurred under darkness. More than 80% of E. spinosa seeds germinated at pH between 6 and 9, whereas E. australis seeds germination was considerably decreased at pH 9. Emex spinosa was fairly tolerant to salinity as compared with E. australis and germination (21%) of E. spinosa occurred even at 200 mM NaCl. Both species were sensitive to osmotic stress, but E. spinosa tolerated more osmotic stress than E. australis. Temperature above 20/12°C (day/ night) and low osmotic potential increased time to start germination and mean germination time (MGT), as well as decreased germination index (GI) of both species. Darkness resulted in increased MGT and decreased GI in both species when compared with 10 h photoperiod. Salt stress strongly increased time to obtain 50% germination and reduced GI of both species. In both species, an increasing burial depth decreased emergence percentage and emergence index and increased time to start emergence, although some seed emerged even at 10 cm burial depth. It was concluded that both species can germinate over a wide range of environmental conditions. However, E. australis was more sensitive under adverse environmental conditions compared with E. spinosa. This information on germination ecology may aid in developing tools and strategies for management.

IntroductionProline is a proteinogenic amino acid, highly essential for various vital metabolic processes within the plant tissues. It is naturally present in plants, microbes, and animals (

-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

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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.

Identification of weed species with allelopathic potential and characterization of their adverse effects against associated crops is required for better understanding of weed-crop interactions. Phytotoxic activity of Euphorbia dracunculoides Lam. on germination and seedling growth of chickpea (Cicer arietinum L.) and wheat (Triticum aestivum L.) was investigated under controlled conditions. Two separate studies were done with each of four organic solvent fractions (n-hexane, chloroform, ethylacetate, 1-butanol) and crude aqueous (1:10 and 1:20) whole plant fractions of E. dracunculoides using distilled water and 0.05% (v/v) dimethyl sulfoxide (DMSO) as control. Different aqueous and organic fractions of E. dracunculoides had a significant bearing on germination attributes and seedling growth that varied among tested species. The final germination percentage of wheat remained unaffected; nevertheless, root and shoot elongation and biomass accumulation in these parts were significantly retarded. Aqueous fractions appeared more phytotoxic than organic fractions and suppressed chickpea germination by 35-53%. These aqueous fractions also reduced root (64-75% and 33-34%) and shoot (18-62% and 21%) length and root (32-33% and 42-46%) and shoot (7-32% and 80-84%) dry weight of wheat and chickpea, respectively. Among organic fractions, n-hexane was more suppressive to test species. Chromatographic analysis revealed the presence of four phytotoxins, furoic, p-coumaric, syringic, and caffeic acids, in aqueous whole plant (1:10) fractions. This study determined the phytotoxic allelopathic activity of E. dracunculoides against wheat and chickpea.

IntroductionAbiotic stresses drastically affect crops by minimizing yield. Plants face many distinctive abiotic stresses at different stages of plant growth and development. Among these stresses, salinity is prejudicious, limiting plant growth and productivity. Salt stress causes various deleterious effects on morphological, physiological, biochemical, and nutritional attributes. The formation of reactive oxygen species (ROS) is the significant consequence of salt stress. The major ROS comprise hydroxyl ( . OH), superoxide (O 2 .-), and hydrogen peroxide (H 2 O 2 ). The high ratios of ROS are responsible for lipid peroxidation (LPO) of tissues and cause deterioration of proteins, green pigments, and DNA (Schutzendubel and Polle, 2002). However, nature has equipped all vegetations with a defensive antioxidant system to counter the oxidative damage caused by ROS (Apel and Hirt, 2004). Plant growth under saline conditions is highly associated with its antioxidant activities, i.e. superoxide peroxidase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and glutathione reductase (GTR) activities. High antioxidant activities will inhibit LPO by eliminating the ROS.Silicon (Si) is an excellent growth promoting agent. Silicon is reported to increase plant growth and stimulate productivity in various crop plants. Si application strengthened the plant biomass, height, and productivity under different stressed conditions (Ahmad et al., 2007). It also triggers growth by providing strength and extensibility to plant cells. It strengthens the endoderm of the mature basal cells and improves the extensibility of apical cells of the roots; thus Si contributes to a strong, extensive, and deep root system. However, it is also a vital element that has an excellent tolerance enhancing potential against abiotic Abstract: A pot culture study was conducted to assess the ameliorative effect of silicon, Melia azadirachta leaf extract, and sugar beet root extract, each applied individually or in different combinations, on salinity-induced detrimental effects in pea (Pisum sativum L.). Salinity markedly inhibited the growth, various gas exchange attributes, total phenol contents, membrane stability index, and productivity. On the other hand, lipid peroxidation, electrolyte leakage, H 2 O 2 content, antioxidant activities, and leaf free proline and glycinebetaine contents were significantly enhanced by salinity. However, exogenously applied Si and phyto-extracts markedly alleviated the salinity-induced drastic effects on growth, gas exchange attributes, and productivity. Both phyto-extracts supplemented with silicon gave highly salinity mitigating effects by markedly improving growth, gas exchange attributes, enzymatic activities, osmolytes, and yield. The phyto-extracts and Si suppressed lipid peroxidation, electrolyte leakage, and H 2 O 2 content by strengthening the enzymatic and nonenzymatic (proline and glycinebetaine) antioxidant defense system. The phyto-extracts and Si application also che...