Epidermal Characterization of Colocasia esculenta (L.) Schott. and Xanthosoma maffafa (L.) Schott. Accessions As Affected by Different Concentrations of Sodium Azide and Potassium Chromate in Nigeria

Epidermal assessment of five accessions of Colocasia esculenta and three accessions of Xanthosoma maffafa exposed to different concentrations of sodium azide and potassium chromate treatments was carried out. Each accession was planted in four different concentrations (2.5, 5, 7.5 and 10 mg/kg) of each chemical, while the accessions planted with no chemical additive served as the control experiment. Results showed that both the treated and control accessions were amphistomatous, but with more stomata on the abaxial epidermis. Four types of stomata (brachyparacytic, amphibrachyparacytic, brachyparatetracytic and brachyparahexacytic-monopolar) were observed in these species. Contiguous stomata were observed on the abaxial epidermes of some treated samples of NXs 002 and NXs 003; control sample of NXs 003 however had contiguous stomata on both epidermes. The mean stomatal index survey showed that in both epidermes, sodium azide treatments induced higher stomatal index in the accessions than potassium chromate treatments. The anticlinal walls were straight in both control and treated accessions except for the abaxial epidermis of NXs 003 treated with 5 mg/kg of potassium chromate that had wavy anticlinal walls. The shapes of the epidermal cells were not affected by the treatments as they were observed to range from quadrilateral to nonagonal in all the accessions. However, some isodiametric and circular shaped epidermal cells were observed on the adaxial epidermis of NXs 002 treated with 7.5 mg/kg of potassium chromate and, on both epidermes of control NXs 003. Statistical evidence showed that the differences in stomatal indices and epidermal cell numbers between the adaxial and abaxial epidermes were significant at 5% likewise the differences between various accessions but the differences between treatments were not significant at P=.05. The study showed that both chemicals were capable of distorting epidermal architecture but sodium azide proved to be more potent than potassium chromate. Based on this, further studies were encouraged for a clearer understanding of the potentials of these chemicals in crop improvement programs.