Effect of aqueous extract of shoot tip of A, pennata(L.) was evaluated on seed germination and seedling growth of P. lathyroides. The result found that aqueous extract from shoot tip(1.25% (w/v) harvested in March to July was the most inhibitory effects, caused completely inhibited germination of P. lathyroides seed, harvested in January to February showed the moderate inhibitory effect(70 to 80%inhibition) and harvested in August to December showed less inhibition effect(20 to 50%inhibition).