MORPHOLOGICAL DESCRIPTORS OF SEED AND SEEDLING FOR IDENTIFICATION OF DHAINCHA (SESBANIA SPP.) ACCESSIONS

Seed and seedling morphology of 110 dhaincha accessions were studied to search new characters that could add information pertinent to their species identification. Four seed coat colours red, brown, grey and black, and two seed shapes cylindrical and rectangular, were observed. Grey coloured, rectangular seeds produced seedlings with swollen radical with violet coloured hypocotyls. Wide variations were observed in the values of other morphological descriptors. Agglomerative hierarchical cluster analysis using quantitative descriptors showed that 110 accessions clustered in to four groups. The first two components (Factor 1 and 2) of principal component analysis explained 62.01% of the total variance of the collected dhaincha accessions. Seedlings with swollen radical and violet coloured hypocotyls, produced from grey coloured and rectangular seeds, were constantly positioned together in a cluster. Seed coat colour, shape of seed and radical, and hypocotyls colour may be used as important morphological descriptors for species identification of dhaincha accessions at the early growth stage. Introduction Floral morphology of dhaincha (Sesbania spp.) plants shows a continuous variation in the field which makes the identification of Sesbania species difficult to the beginners. Three species of Sesbania viz. S. sesban (L.) Merr. , S. bispinosa (Jacq.) Wight and S. cannabina (Retz.) Poir. , are commonly known as dhaincha in Bangladesh (Ahmed et al. 2009). Seed and seedling characters have emerged as very important morphological descriptors for identification of a species (Sanyal and Paria 2015). Seed colour and shape also help in identifying genetic variability in seed (Sajjad et al. 2012). Seed and seedling growth are governed by morphology and other derivatives. Source of seed and its genetic behavior denote seedling variability. Seedling morphology of flowering plants can help for taxonomic identification of concerned to morphology and others purposes (Ahammed and Paria 1996), and seedling characters are as important and reliable as that of floral one in the delimitation of species, genera and even families (Sanyal and Paria 2015). Seeds and seedlings also reveal much information about ecological as well as evolutionary profile of higher plants (Sousa and Sousa 1981). The morphological observation of Sesbania seedlings has been carried out by many workers (Sousa and Sousa 1981, Monteiro 1984, Srivastava and Kumar 2016). Monteiro (1984) described five principal characteristics of Sesbania seedlings: (i) Epigeal germination with a long hypocotyls and short epicotyls, (ii) foliaceous cotyledons, very short petiolate and escaping from the testa, (iii) first eophyll simple and resembling the cotyledons, (iv) second eophyllparipinnate with fewer leaflets than the metaphylls, and (v) epicotyls longer than the internodes between the first metaphylls. Although the characters of seedlings are limited in number, their diversity is large and thus their assemblages serve the purpose of identification (Welling and Laine 2000). Therefore, the present study was undertaken to investigate new characters of morphological importance for identification of dhaincha accessions at the early stage of growth. *Author for correspondence: <drsarwar@bau.edu. bd>.