TAXONOMIC DELIMITATION OF SPECIES OF SENNA AND CASSIA IN AHMADU BELLO UNIVERSITY, ZARIA
TAXONOMIC DELIMITATION OF SPECIES OF SENNA AND CASSIA IN AHMADU BELLO UNIVERSITY, ZARIA
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Date
2018-08
Authors
GARBA, Fatima Nuru
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Abstract
ABSTRACT
The foliar epidermal characters of species of Sennaand Cassiawhichincludes; Senna alata (L.) Roxb., S. hirsuta (L.) Irwin and Barneby, S. obtusifolia (L), S. occidentalis (L.), S. siamea (Lam.), S. singueana (L), S. siberiana (L) and Cassia absus were studied in Ahmadu Bello University, Zaria in search for useful taxonomic characters. Features such as leaf base, leaf apex, leaf shape and leaf texture were assessed for variances in morphological characters. Stomata and trichome studies (adaxial and abaxial)were conducted where the stomatal type, trichome type and stomata length, width and size were evaluated using a caliberated eye piece micrometer. For internal anatomy, histological technique was used.Acetolysis technique was adopted for flower bud studies. The scanning electron microscope was used for seedcoatsculpture study. All species were shruby except for senna siamea and S. alata which were trees. The stomata found were paracyticand anisocytic in S. obtusfoliaand S. occidentalis, anisocytic in S. siameawhile for S. hirsutae and S siberiana,they were paracytic all through. Therewasvariability in the stomatal length which was largest in S.hirsutae(2.22μm) and shortest in S.siamea (1.32μm). Thefrequencyof stomata was highest in S. hirsutae (42.75μm) and lowest in S.obtusfolia (18.55μm). The pollen grains were radially symmetrical with few variations in length which was highest in S.singueana (27.20μm) and lowest in C.absus(1.58μm), width of pollen grain was widest in S.occidentalis (9.40μm) and in narrow C.absus (1.04μ). Based on surface sculpturing pattern: parallel crack was exhibited in S. alata and S. siamea while random cracks were seen in S. siberiana and S. occidentialis,C. absus had no cracks.For palisade cell number,the highest was observed in S.hirsutae(39.20μm) and the lowest in C.absus (20.80μm). The thickness of the epidermis also varied, C.absus (28.88μm) had the thickest epidermis while lowest was in S. siberiana (6.35μm). Thedifference in stomatal, pollen and trichomefeaturesareofhigh taxonomicvaluein theclassificationofthesespecies. The study revealed that seed coat ornamentation within the genus shows considerable variation and can be helpful for taxonomic purposes. A dichotomous taxonomic key is hereby presented to aid the identification of the studied Sennaand Cassia species. In conclusion,the similarities in structure of seedcoat and morphology showed interspecies relationship. They are placed in the same family due to similarities in morphology, while the differences in morphology led to speciation. The sculpturing details of the seed coat varied between species and have been able to show that they possess different cracks arrangement which can be used at both generic and species levels.
Description
A DESSERTATION SUBMITTED TO THE SCHOOL OF POSTGRAUDUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A MASTERS DEGREE IN BOTANY
Keywords
TAXONOMIC,, DELIMITATION,, SPECIES,, SENNA,, CASSIA,, AHMADU BELLO UNIVERSITY,, ZARIA