Could the Three Be Edible and Natural Sources of Levodopa? Morphological Characterization of Three Taxa of Mucuna (Fabaceae) in Ebonyi State, Southeastern Nigeria

Background: There were reports that M. pruriens was edible and natural source of Levodopa used in the treatment of Parkinson’s disease, but the identity of the variety used for the treatment is uncertain. Hence, the present study is important to provide their diagnostic characters for further studies by prospective researchers. Methods: The qualitative study was carried out by observing and recording the features of the taxa while the quantitative was obtained as the leaflet length and width were measured using a metre rule. From each specimen, leaves were randomly selected and measured using metre rule. Standard methods were used in this study. Result: The three taxa possess trifoliate leaves in common and the flower colours are as follows: Yellow in M. flagellipes, purple in M. puriens var. pruriens and white in M. pruriens var. utilis. Testa colours are black, black and white in the M. flagellipes, M. pruriens var. pruriens and M. pruriens var. utilis, respectively. The highest average leaflet length was 17.5 recorded in M. pruriens var. pruriens while the lowest average leaflet length of 8.4 was recorded in M. pruriens var. utilis. The three taxa could be eaten based on review. Petal and testa colour could be used to distinguish the taxa studied.

Association of differences in seed vigour in long bean (Vigna sesquipedalis) with testa colour and imbibition damage

SUMMARYField emergence of 11 seed lots from six cultivars of long bean, all having laboratory germination of > 80%, ranged from 0 to 83%, indicating differences in seed vigour. Vigour differences occurred within and between cultivars, seed lots from cultivars with white or partly white testas having particularly poor emergence (0–21%) compared with those with brown or black testas (41–83% field emergence). The significant ranked correlations between field emergence and (i) solute leakage, measured by the electrical conductivity of seed soak water (r = –0·864), (ii) the percentage of cotyledons made up of completely living tissue, revealed by vital staining (r = 0·895), and (iii) the proportion of hard seeds (r = 0·916) indicated that lots with low vigour and potentially poor field emergence could be identified before sowing. Seed lots having low vigour imbibed water rapidly; the improved vital staining when seeds imbibed slowly indicated that damage occurred during imbibition and was a cause of low seed vigour. Rapid water uptake by low-vigour seed lots was partly explained by the incidence of seeds with cracked testas, but other factors could not be eliminated. The significance of differences in water uptake between cultivars differing in testa colour is discussed in relation to breeding for improved emergence.

Variation in tannin content in Vicia faba L.

SUMMARYThe tannin content of milled seed of 55 lines of Vicia faba was evaluated and related to flower and testa colour, seed weight and percentage of testa. Tannin content in the lines analysed was related more to flower colour than to testa colour. No relationship existed between tannin content and seed weight. Lines with low tannin content had a low proportion of testa.

Seed vigour in cultivars of dwarf French bean (Phaseolus vulgaris) in relation to the colour of the testa

SUMMARYDifferences in the field emergence of 30 commercial seed lots of dwarf French beans were associated with the colour of the testa, the 11 lots with a white testa having a lower mean field emergence of 67% compared with 91% for lots with black (11 lots) or brown (8 lots) testae. The white-seeded lots also had higher leachate conductivities (mean 42 μ S/cm/g) and imbibed more rapidly (an average 43% weight increase after 6 h imbibition) than black- or brown-seeded lots (average 25 μS/cm/g; 30% weight increase). The extent of damage to the testa which was slight in all lots was not related to differences in either the field emergence or rate of imbibition of the lots. In two successive imbibition cycles seeds of Provider (brown testae) took up water far more rapidly in the second imbibition (78% weight increase after 3 h) than the first (25% weight increase). The coloured testae normally adhere very tightly to the cotyledons but were loosened following the first imbibition leading to a more rapid uptake of water. The rapid imbibition of Tenderette (white testae) which has a loose fitting testa even in the dry seed was increased only slightly by a second imbibition. When seeds were imbibed from one end only from which the testa was removed Tenderette imbibed rapidly (90% weight increase after 12 h) whereas in Provider the tightly adhering testa limited the rate of water uptake (42% weight increase after 12 h) despite the ready access of water to the seed. It is suggested that the degree of adherence of the testa to the cotyledons is the major factor influencing the rate of imbibition of cultivars of dwarf French beans differing in testa colour and its role in determining seed vigour is discussed.

In vitro digestibility of the testa in tannin-free field beans (Vicia faba L.)

SummaryThe seed-coat of all white-flowered varieties of Vicia faba and segregants tested was free of tannin. In two field trials, the whole grain of white-flowered varieties wassignificantly higher in in vitro digestibility of the dry matter, on average 4·7% higher, than coloured-flowered varieties of similar seed size. In subsequent trials where the testa and cotyledon were examined separately, this difference was shown to be largely due to a mean D value (digestibility of the organic matter) of the testa in tannin-free varieties of 56·4% compared with 17·2% in tannin-containing varieties. Seed size was positively correlated with D value but not because of differing proportions of testa.Differences between varieties in acid-pepsin solubility and protein content of the testa were much smaller and not associated with presence of tannin. The testa colour of some tannin-free F2 plants was a darker shade of grey than either parental population. An inbred line completely lacking in anthocyanin in flowers and stem but with the normal black wing spot had tannin in its testa.Grains of peas from the coloured-flowered variety, Minerva, reacted to a tannin test wheieas those from white-flowered varieties, Greenshaft and Flavanda, did not.The case for breeding further tannin-free varieties of Vicia faba is discussed.