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 conduct ed to determine if internode senescence is an indicator of mineral con tent 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, Ok la., in a Bernow fine-loamy (siliceous, thermic Glossic Paleudalf) soi l. At fresh market harvest senescence rating and amounts of Kjeldahl n itrogen (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 deter mined. Senescence ratings were higher with later planting dates and in ternodes were higher on the stalk. Senescence ratings were different f or genotypes. About 0.3% of N was NO2- and NO3-, and about 30% of P wa s HPO4-2. Nitrogen and Na+1 content decreased with delayed planting da te. Lowest total P and highest K+ contents were in plants sown on 30 A pril. 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. Cont ents of total N, total P and K+ were significantly different for genot ypes. Mineral contents were not significantly correlated with senescen ce ratings in internodes.