Phytotoxic Effect of Tithonia rotundifolia (Miller) S.F.Blake on Chlorophyll and Protein Contents of Vigna unguiculata L. and Zea mays L.

Abstract

A large number of plants impose inhibitory effects on the germination and growth of neighbouring or successional plants by releasing allelochemicals into the soil. This study investigated the phytotoxic effects of Tithonia rotundifolia (Miller) S.F.Blake on the chlorophyll and protein contents of Vigna unguiculata (L.) Walpers and Zea mays L.. This was with a view to determining the susceptibility of these crops to allelochemicals in the extracts prepared from T. rotundifolia. Seeds of the test plants were sown in pots filled with top humus soil. At two weeks, seedlings in each pot were thinned down to 10 seedlings per pot. Potted plants of the test crops were supplied with 400 ml of the appropriate water extracts while the control potted plants were supplied with 400 ml of water. Biochemical analyses were carried out according to standard methods. The data obtained were analysed by (ANOVA) to determine significant (P< 0.05) effects. The means were compared using Duncan Multiple Range Test. The chlorophyll a, chlorophyll b, total chlorophyll and protein contents in V. unguiculata and Z. mays and were significantly inhibited by the extract from T. rotundifolia. The inhibitory effects of these allelochemicals increased with concentration. The phytotoxic effect of T. rotundifolia was species dependent. It was concluded that the extract contains water-soluble allelochemicals which inhibited the biochemical parameters of the test crops. T. rotundifolia should be controlled where it grows in association with cultivated crops.