Leaf extract of Parthenium hysterophorus L. affects the growth of Cajanus cajan (L.) Millsp

Cajanus cajan is an important pulse crop of India and Parthenium hysterophorus is an invasive weed of agroecosystem. The main aim of this study was to evaluate the effect of leaf extract of Parthenium hysterophorus of different concentrations on the rate of seed germination and seedling growth of Cajanus cajan, and to know the allelopathic effect is the main cause of success of P.hysterophorus in the fallowland which supports novel weapons hypothesis. In petridishes in three replicates the effect of different concentrations were evaluated on seed germination and seedling growth compared to control condition. The experiment was conducted in the laboratory of Department of Botany, J.P.University, Chapra, Bihar, India during the month of April 2016. Laboratory temperature during the study period varied from 35 to 40C. Fresh leaves of Parthenium hysterophorus were collected, dried in laboratory and crushed to prepare powder. Different concentrations (15%, 25%, 50%, 75% and 100%) of leaf extract were prepared. In petridishes 10 seeds in triplicate were maintained with control condition of Cajanus cajan. After seven days per cent seed germination, length of root and shoot, R: S ratio, fresh weight of seedlings and seed vigour index (SVI), per cent inhibition in germination, root and shoot relation elongation ratios were determined. Standard errors were calculated, t-test and linear as well as multiple regression analyses were done. The effects on different parameters studied were more inhibitory for 100% treatment than the other treatments. The rate of seed germination in control was 96.67% whereas this value was 0.01% in 100% of leaf extract. However in other treatments these values ranged from 60% to 86.67%. The range of seed germination reduced from -10.34 to -62.07% in different concentrations of leaf extract of Parthenium hysterophorus. The effect of different concentrations of leaf extract of Parthenium hysterophorus on root length of Cajanus cajan was more than the shoot length in the present study. In case of shoot length the values ranged from 9.05 to 4.41cm compared to control condition (8.26 cm) whereas in case of root length the values ranged from 5.11 to 1.16 cm in different treatments compared to control condition (3.92 cm). T-test and regression analysis indicated negative impacts of leaf extract of P.hysterophorus on C.cajan.This study indicated that the higher concentration of leaf extract of Parthenium hysterophorus was more inhibitory than other treatments for Cajanus cajan. The allelopathy is the main cause of invasion of P.hysterophorus that supports the novel weapons hypothesis.