Pure Appl. Biol., 8(1): 187-198, March, 2019 http://dx.doi.org/10.19045/bspab.2018.700176 Published by Bolan Society for Pure and Applied Biology 187 Research Article Allelopathic potential of Cassia fistula against Lactuca sativa, Setaria italica and Pennisetum americanum Zahir Muhammad 1* , Naila Inayat 1 , Rehmanullah 1 , Wisal Muhammad Khan 2 and Abdul Majeed 3 1. Department of Botany, University of Peshawar, Peshawar, Khyber Pakhtunkhwa-Pakistan 2. Department of Botany, Islamia College Peshawar, Khyber Pakhtunkhwa-Pakistan 3. Department of Botany, Govt. Degree College Naguman, Peshawar, Khyber Pakhtunkhwa-Pakistan *Corresponding author’s email: kzahirmuhammad@yahoo.com Citation Zahir Muhammad, Naila Inayat, Rehmanullah, Wisal Muhammad Khan and Abdul Majeed. Allelopathic potential of Cassia fistula against Lactuca sativa, Setaria italica and Pennisetum americanum. Pure and Applied Biology. Vol. 8, Issue 1, pp187-198. http://dx.doi.org/10.19045/bspab.2018.700176 Received: 04/05/2018 Revised: 06/10/2018 Accepted: 18/10/2018 Online First: 25/10/2018 Abstract Plants during different phases of growth produce secondary metabolites which have multipurpose roles. One of the aspired roles associated with the production of such compounds is their active involvement in allelopathy –a phenomenon of the chemical interactions of plants and/or microorganisms. Investigation of the allelopathic properties of different plants is useful in agriculture as it would lead to the proper cultivation of crops under field conditions with respect to allelopathic plants. This study was aimed at exploring the allelopathic effects of Cassia fistula aqueous extracts obtained from leaves, bark, and fruit on germination and growth of Lactuca sativa, Setaria italica and Pennisetum americanum. Results demonstrated that aqueous extract from leaves, bark, and fruit of C. fistula had differential toxicity against the Lactuca sativa, Setaria italica and Pennisetum americanum. Phytotoxicity of extracts depended upon the concentration soaking duration. It was observed that 24-hour extracts were more inhibitory. Leaf extracts exhibited more toxicity than bark and fruit. Lactuca sativa was found more sensitive to the applied allelopathic stress of C. fistula than Setaria italica and Pennisetum americanum. Based on our results, it is suggested that Cassia fistula has strong allelopathic potential and may serve as a potential candidate for using its allelopathic potentials in weed control strategies. Keywords: Allelochemicals; Allelopathy; Cassia fistula; Phytotoxicity; Weed control strategies Introduction The term “allelopathy” infers to the communications between plants and/or microbes which might lead to either stimulation or inhibition of growth, physiology, and development of plants and other organisms by the release of secondary molecules termed as ‘allelochemicals’ [1]. In nature, different groups of plants like algae, lichens, crops, and weeds have well established allelopathic properties which are thought to be an evolutionary mechanism adopted by plants to survive in the given environment and to determine their success over susceptible plant species [2, 3]. Diverse phytotoxic substances causing germination and/or growth inhibitions have been isolated from several plants and their tissues, which