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Excessive use of herbicides in the crop field threatens the environment by destroying flora and fauna. Allelopathic substances might be proved as a substitute of chemical herbicides to suppress the target plants. In this study the Jaman (Syzygium cumini) leaves were extracted with H2O for its constitutional composition and then its allelopathic effects were investigated against pre- and post-germinated wheat and canary grass. By HPLC, total eight components were identified by comparing the chromatograms of the unknown with standard ones. The pre- and post-germinated bioassays were taken into consideration for wheat and canary grass separately. The results showed that over all 70% aqueous methanol extract of jaman leaves (2.5%-10%) increased the length of shoot and root linearly for both pre-germinated wheat bioassays (11.00-15.75 cm and 9.50-10.75) and post germinated wheat bioassays 14.50-17.00 cm and 10.35-12.75 cm, respectively) as compared with control ones. Similarly allelochemicals of jaman leaves depressed both the pre-germinated and post-germinated bioassays of canary grass as compared with control ones (6.75 - 1.75 cm and 4.25-0.90 cm for shoot and 4.00-0.45 cm and 1.85-0.30 cm for root, respectively). These results reveal that growth inhibition components may be present in the Jaman (Syzygium cumini) leaves and also certain components may be responsible for the allelopathic potential. Therefore, leaves of the titled plant may provide a possible material for the isolation and identification of allelopathic substances and may be helpful for the development of new natural herbicides [ABSTRACT FROM AUTHOR]

Excessive use of herbicides in fields threatens the environment by destroying flora and fauna. Allelopathic substances might be proved as a substitute of chemical herbicides to suppress the target weeds. In this study, the Psidium guajava L. leaves were extracted with 70% (v/v) methanol for the constitutional composition. The allelopathic effects were investigated against pre- and postgerminated wheat and canary grass seeds. Among the evaluated 16 allelochemicals, some eight components (Ellagic acid, 3,4- dihydroxybenzoic acid, Feruic acid, Galluic acid, Vivillic acid, 3- hydroxy-benzoic acid, Gallic acid and p-coumaric acid) were identified by comparing the chromatograms of the unknown with standard ones. The pre- and post-germinated bioassays were taken into consideration for wheat and canary grass separately. The results showed that over all 70% methanol extract of P. guajava L. leaves (2.5-10%) increased the shoot length and root linearly for both pre-germinated wheat bioassays (14.0 - 16.5cm and 12.9 - 15.0cm and post germinated wheat bioassays 13.85 - 16.25 cm and 11.15 - 14.50 cm, respectively) as compared with control ones. Similarly, allelochemicals of P. guajava L. suppressed both the pregerminated and post-germination bioassays of canary grass as compared with control ones (7.35 - 0.45cm and 6.50 - 2.75cm for shoot and 1.65 - 0.05cm and 2.15 - 0.75cm for root, respectively). These results suggest that P. guajava L. may contain growth inhibitory substances and may possess allelopathic potential. Therefore, leaves of P. guajava L. may be a possible candidate for the isolation and identification of allelopathic substances and for the development of natural herbicides for sustainable agricultural production. [ABSTRACT FROM AUTHOR]

The present investigation was carried out to assess the concentration of cadmium (Cd) and lead (Pb) in 20 herbage and 80 ewe's milk samples collected on different intervals in Sargodha, Pakistan. The higher concentration of Cd in the herbage showed maximum concentration (0.063mg/kg) during September and lowest (0.031mg/kg) during October. The Pb was likewise highest (0.043 mg/kg) during September and lowest (0.028 mg/kg) during November These metal concentrations in the herbage were far lower than the toxic levels already established for livestock. In the milk samples the highest Cd concentration (0.253mg/L) was recorded in October and the lowest (0.193 mg/L) during December. The Pb concentration was highest (0.160 mg/L) during the month of November and the lowest (0.090 mg/L) during December. These results showed that metal concentration were lower than those recommended by the International Standards and Codex. [ABSTRACT FROM AUTHOR]