Description of seed and pollen micromorphology and their taxonomic impact in some Solanum L. species

Abstract

Seed micromorphology, of 17 species and pollen micro-morphology of 16 species of Solanum L. (Solanaceae) were examined using both light and scanning electron microscopy (SEM) to determine the significance of seed coat features and pollen variations as taxonomic characters. The species, used in this study, represent three subgenera and 11 sections of Solanum in Egypt. Macro and micro-morphological characters including seed shape, size, colour, surface; hilum shape, size, position, level; seed coat ornamentation, cell wall; shape of pollen in both polar and equatorial views, colpus membrane and apices beside exine ornamentation have been described and their taxonomic impacts have been outlined. Seed shape was either obovate or reniform and their sizes range between 1.22 ± 0.19 and 3.05 ± 0.91 mm in length and 1.14 ± 0.21 to 3.28 ±0.63 mm in diameter. Four types of seed coat appearance have been described: reticulate, cerebelloid, striate and without conspicuous cell lumen. Palynological study revealed six types of pollen shape within the studied species: prolate, subprolate, spheroidal, prolatespheroidal, oblate-spheroidal and perprolate. Pollen length in polar view ranged from 15 ± 0.50 µm to 34 ± 2 µm but in the equatorial view it ranged from 9.06 ± 1.94 µm to 25 ± 2 µm. Four types of exine ornamentation have been recognized: scabrate, psilate, granulate and verrucate. Nineteen characters of seed and pollen micromorphological features gave useful tools in the construction of a dichotomus indented systematic key for the examined species. The major remarks are the differentiation of by their reniform seed shape from the remaining species which have ovoid seed shape. Seed coat sculpture and pollen grain feature were useful traits for the identification of the other nine taxa.