Effect of Parthenin—A Sesquiterpene Lactone from Parthenium hysterophorus—On Early Growth and Physiology of Ageratum conyzoides

A study was undertaken to assess the effect of parthenin—a sesquiterpene lactone from Parthenium hysterophorus—on the germination, growth, and some associated physiological changes in Ageratum conyzoides. The study reveals that germination and growth of A. conyzoideswas severely reduced by parthenin in the concentration range of 50, 100, and 200 μM, while at 400 μM a complete inhibition of germination was observed. The radicle length of A. conyzoideswas reduced more than the plumule length. Further, the content of the photosynthetic pigment chlorophyll was appreciably reduced in the leaves of test plants spray treated with parthenin at 200 μM concentration. However, this inhibitory effect declined with the passage of time and at 10 days after treatment only a 25% reduction in chlorophyll content was observed compared to 76% on the first day after spray. Likewise, the cellular respiration measured through 2,3,5-triphenyl tetrazolium chloride was found to be less in the treated leaves, and the inhibitory response also declined with time. The content of proteins and carbohydrates decreased with the passage of time after parthenin treatment. The specific activities of the enzymes protease and α- and β-amylase were also adversely affected in the parthenin treated leaves. In the case of protease, the activity decreased with passage of time while those of the amylases increased. Thus, we conclude that parthenin affects the germination and growth of A. conyzoidesby altering the contents of some macromolecules and the specific activities of some enzymes. Such observations may be helpful in further exploring parthenin's mode of action.