Ascorbic acid content in leaves of Nightshade (Solanum spp.) and spider plant (Cleome gynandra) varieties grown under different fertilizer regimes in Western Kenya
Vitamin C is an important micronutrient because of its antioxidant and health promoting properties. With the introduction and commercialization of improved African indigenous plants, few studies have examined the impact of leaf age or the nutrient status of the plants by fertilizer. This study sought to determine amounts of vitamin C using redox titration in mature and immature leaves of spider plant (Cleome gynandra) and black nightshade (Solanum ssp) grown in fields and subjected to various sources of fertilizers which were chicken manure to provide an organic source, Mavuno fertilizer to provide a conventional synthetic source and no fertilizer to serve as a control. Chicken manure led to the highest (167 mg/100 g) vitamin C content which was however not statistically significant from Mavuno fertilizer (150 mg/100 g) at P≤ 0.05 in the nightshade variety. The highest vitamin C with no fertilizer application was 105/100 g and 79 mg/100 g in SS-49 and UG-SF varieties respectively. Moreover, vitamin C content was highest in mature leaves than in immature ones whatever the kind of fertilization treatment applied. By recognizing the impact of leaf age and importance of providing adequate fertilization, farmers can produce higher yielding and more nutritious leafy greens.
Keywords: Leaf age, vitamin C, fertilizers, plant nutrition, spider plant, nightshade