Herbicidal potential of Breynia retusa leaf extract on Calotropis gigantea, Parthenium hysterophorus, Datura metal and Tridax procumbens

Aqueous leaf extract of the herb, Breynia retusa (Dennst.) Alston was studied for its herbicidal activity against four common weeds: Calotropis gigantea (R.Br.), Parthenium hysterophorus (L), Dathura metal (L) and Tridax procumbens (L). Foliar application of the water diluted extract caused chlorosis and necrosis in the treated plants. Its crude leaf extract acted as contact herbicide. Changes in the plant growth, morphological aberrations, and color loss were the major changes. The extract initially killed only the parts of the plant that were sprayed/exposed to extract but later the entire plant was defoliated. The extract was selective in herbicidal activity and did not affect rice (Oryzae sativa L.) and wheat (Triticum vulgare Vill.) crops seed germination. The effects of extract were also studied on RNA, DNA, proteins, free amino acids, glutamine, chlorophyll and ammonia. Thus B. retusa has allelopathic effects on several common weeds and may be developed as an effective weed control agent.