Relationship between seed coat colour and imbibition characteristics of African Yam bean (Sphenostylis stenocarpa (Hochst. Ex. A. Rich.) Harms) Seeds

Ogunleye, Yetunde Odunola (2019)

viii,50p

Thesis

The study investigated the relationship between coat colour and composition of African yam bean seeds; investigated the relationship between seed composition and the amount and rate of water imbibition characteristics of African yam bean seeds; and also investigated the influence of seed coat colour and composition on seed vigour of African yam bean (Sphenostylis stenocarpa [Hochst Ex. A. Rich] Harms).This was with a view to determining the influence of seed coat colour and chemical composition on imbibition of African yam bean. Seeds of four cultivars of African yam bean were sorted into four colour classes using Munsell Soil Colour Chart. Imbibition test, hundred seed weight, standard germination test, and bulk conductivity test were conducted on the seeds by class. Biochemical analyses were also carried out to determine the seed chemical composition. Means were separated using Fisher’s Least Significant Difference (LSD). The results showed high significant differences (P<0.01) among the four coat colours of African yam bean for ash content, fat content, fibre content, quantity of protein, amount of carbohydrate and total phenol in the seed coat. The mean values for the four different colours of African yam bean showed that hundred seed weight ranged from 24.42 g in pale brown to 30.17 g in mottled light yellowish brown colour. Mottled light yellowish brown colour had the highest germination percentage (93.50%) while reddish brown colour had the least germination percentage (36.50%). Considering the vigour, light greenish gray had the highest conductivity value (2.99 μS cm‾1g‾1) while mottled light yellowish brown had the least value (0.98 μS cm‾1g‾1) indicating that mottled light yellowish brown had the highest vigour among them. The peak of imbibition occurred at 24th hour for light greenish gray (32%), mottled light yellowish brown (23%) and pale brown (17%), except reddish brown colour (7%) whichviii had the peak of imbibition at 30th hour. Light greenish gray seeds imbibed high amount of water within 54 hours compared to other seed colours (mottled light yellowish brown, Pale brown, Reddish brown) which took more than 54 hours to imbibe water but had lower germination percentage due to highest amount of fat in the seeds. Imbibition rate was fastest in light-coloured seeds due to high carbohydrate content. Generally, there was no relationship between seed composition and amount of water imbibed, but the lighter the colour of the seeds, the higher the fat content. There was a positive relationship between fat content and the rate of imbibition. The study concluded that seed coat colour was not related to water imbibition while chemical composition significantly influenced the vigour but seed coat colour per se did not