Allelopathic competitiveness of Trianthema portulacastrum L. and Parthenium hysterophorus L. on morphological and physiological growth parameters in okra

摘要

Okra is an essential vegetable world over, but in past decade, a reduction in per hectare yield was noted. Amongst various reasons for its low yield, weeds are the most important. These weeds reduce the crop growth by competing for resources and by allelopathic effects. During surveys of okra fields in Pakistan, amongst others, Trianthema portulacastrum L. and Parthenium hysterophorus L. were noted but no data till to date are available that show comparative allelopathic potential of these weeds in okra. So, in the recent investigation, experiments were executed to assess the allelopathic effects of these two weeds on okra. Soil amendment with T. portulacastrum significantly reduced the shoot length of okra up to 42%, root length up to 73%, shoot dry weight up to 84%, root dry weight up to 73% and chlorophyll a up to 48%, chlorophyll b up to 50% and carotenoid up to 19.5%. Similar inhibitory effects were observed in case of P. hysterophorus but with comparatively less intensity. Gas Chromatography Mass Spectrometry analysis of T. portulacastrum revealed the presence of compounds viz., Phytol, 11-octadecenoic acid, methyl ester, 8, 11-Octadecadienoic acid, metlyl ester and Pentadecanoic acid at the highest concentrations. While in case of P. hysterophorus, following compounds were present at the highest concentrations; Phorbol, 1, 2-Benzenedicarboxylic acid, mono (2-ethylhexyl) ester, Isolongifolene-7, 8-dehydro8a-hydroxy- and 1H-cycloprop[e]azulene, 1a, 2, 3, 4, 4a, 5, 6, 7b-octahydro-1, 1, 4, 7-tetramethyl-, [1ar (1a.alpha., -4.alpha., 4a.beta.,7b.alpha.)]-. It can be concluded that these compounds may be responsible for allelopathic effects observed during the present study.