MICROSTRUCTURE OF BLACK, GREEN AND RED GRAM

The three most commonly consumed legumes (grams or pulses) in India, b lack gram (Vigna mungo (L.) Hepper), or urd, green gram (Vigna radiata (L.) Wilczek) or mung, and red gram (Cajanus cajan (L.) Millsp.) or t ur, were examined by scanning electron microscopy. Seed coat and inter nal features were examined to differentiate these legumes from common beans (Phaseolus vulgaris), adzuki beans (Vigna angularis) and lentils (Lens culinaris). Cross-sections of the seed coats of black, green an d red gram contained single layers of columnar palisade cells extendin g as double palisade layers at the hilum regions. The funiculi located above the hila contained storage cells; some cells were possibly coll apsed during abscission from the seeds. The seed coat surface of red g ram exhibited randomly distributed pits associated with surface deposi ts. Red gram exhibited prominent ridges above the hilum. The sub-epide rmal region of red gram seed coat contained elongated pillar-shaped ce lls, generally called hourglass cells. Pillar cells were also present adjacent to the hilum region of both black gram and green gram seed co ats, but were absent in the seed coat away from the hilum region. Star ch granules embedded in a protein matrix were observed in the cross-se ction of cotyledons of each of the grams. Additional characterization of the microstructure of legumes will contribute to seed identificatio n, and aid the understanding of changes that occur with development of the ''hard-to-cook'' phenomenon and during preparation, processing or cooking of legumes.