MINERAL CONTENT AND SENESCENCE IN SWEET CORN STALK TISSUE AT FRESH MARKET HARVEST

Various internodes in sweet corn (Zea mays L.) stalks at fresh market harvest exhibit different stages of senescence. This study was conducted to determine if internode senescence is an indicator of mineral content in internodes. On 2, 19, and 30 April and 14 May, 1993, seeds of standard sugary (su), sugary enhancer (heterozygous, Sese; homozygous, sese), and shrunken2 (sh2) sweet corn cultivars were sown at Lane, Okla., in a Bernow fine-loamy (siliceous, thermic Glossic Paleudalf) soil. At fresh market harvest senescence rating and amounts of Kjeldahl nitrogen (N), NO3−, NO2−, total phosphorus (P), HPO4−2, K+, SO4−2, Ca+2, Fe+1, Mn+1, Mg+2 and Na+1 in internodes near the base of the stalk, subtending the ear, and between the ear node and the tassel were determined. Senescence ratings were higher with later planting dates and internodes were higher on the stalk. Senescence ratings were different for genotypes. About 0.3% of N was NO2− and NO3−, and about 30% of P was HPO4−2. Nitrogen and Na+1 content decreased with delayed planting date. Lowest total P and highest K+ contents were in plants sown on 30 April. Content of total N was not changed, total P increased, and those of K+ and Na+1 decreased as internodes were higher on the stalk. Contents of total N, total P 'and K+ were significantly different for genotypes. Mineral contents were not significantly correlated with senescence ratings in internodes.