Abstract
The effect of allelopathy on many aspects of plant ecology including occurrence, growth, and structure of plant communities, dominance, and diversity has had a check red history among ecologists. Field studies showed the increase of Amaranthus viridis density in an infested area by Trianthema portulacastrum more than uninfested area, while no difference in soil physicochemical characters at both areas. Bioassay was done under two different temperatures 25 and 35 degrees C with different types of T. portulacastrum leaf and stem extracts. The untreated seeds showed very small germination percent at the high temperature, while the treated seeds showed very high percentage. Different types of extracts had highly significant increase in seed germination, radicle and plumule growth of A. viridis. Treatment by T. portulacastrum extracts increased soluble protein, amylase and total phenol of A. viridis. Stimulation of all the previous parameters was higher in high temperature than in the lower. HPLC analysis for T. portulacastrum leaf and stem estimated eight phenolic compounds. The present study supports the ecological importance of allelopathy in Agriculture.