ABSTRACT

Experimentswere conducted to evaluate the effect of Alectra vogelii (Benth) aqueous extract

on the growth of cowpea (Vigna unguiculata (L.) Walp) varieties. The laboratory screening experiment was conducted at the Deparment of Biological Sciences and the pot experiment was carried out at the Institute for Agricultural Research, Ahmadu Bell Univesity, Zaria. The qualitative and quantitative phytochemical screening of Alectra vogelii plants was conducted at National Research Institute and Chemical Technology, Zaria. The physico-chemical analysis of the soil used was carried out in the Department of Soil Science, Faculty of Agriculture, Ahmadu Bello University, Zaria. In the laboratory screening the effects of Alectra vogeliiaqueous extract was evaluated at 0, 25, 50, 75 and 100 g/l. The parameters taken in the laboratory experiment include seed germination on daily basis for 10 days, shoot and root length (cm) and seedlings weight (g) of cowpea were taken 10 day after planting. In the pot experiment 0, 50, 100, 150 and 200 g/l of Alectra vogelii aqueous extract was tested. Parameters taken in the pot experiment include the number of leaves, plant height (cm), number of root nodules, shoot and root fresh and dry weight (g) of the cowpea at 5, 7 and 9 weeks after planting. The phytochemical composition of Alectra vogelii plant showed the presence of saponins with the highest percentage (46.50 %), followed by flavonoids (16.04 %), tannins (0.247 %), cyanogenic glycosides (0.212 %) and the least was alkaloids (0.08 %). Alectra vogelii aqueous extract at 25-100 g/l significantly reduced cowpea seeds germination, root and shoot lengths and seedling weight at 10 days afteqar planting in the laboratory screening test in all the cowpea varieties. In the pot experiment, Alectra vogeliiaqueous extract treatments at 50 - 200 g/l reduced significantly all the growth parameters (root and shoot fresh and dry weight, plant height, number of leaves and root nodules) in cowpea varieties compared with the control. This reduction was concentration dependent and was highest at 200 g/l Alectra extract treatment. In some occasions, growth values under 50 g/l Alectra extract was comparable with that of the control and also that under 150 g/l comparable with that of 200 g/l Alectra extract treatment. In conclusion, the laboratory and pot experiments showed that,Alectra vogeliiaqueous extract reduced seed germination and all the growth parameters of cowpea varieties. Therefore, it is necessary to remove Alectra vogelii residues from farms as they can inhibit the germination and growth of cowpea due to the allelochemicals thatAlectra vogelii plant contains.

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