The effects of Biozyme on the germination and emergence of bean (Phaseolus vulgaris L.) and sweet corn (Zea mays L.) seeds under suboptimal temperatures, pesticide overdose, and salinity stress

Abstract

The effect of Biozyme-, a commercial germination stimulant, on the germination and emergence of bean and sweet corn seeds, treated with four levels of Carbofuran and Chlorothalonil, and grown under suboptimal temperatures, was evaluated. Field experiments consisted of two plantings that provided suboptimal temperatures during emergence. Pesticide overdoses caused significant detrimental effects to all emerging seedlings. These effects were magnified under the low temperatures of the first planting. BiozymeTm improved the performance of sweet corn in both plantings. In beans, however, BiozymeTm had negative effects in the first planting, while proving beneficial in the second planting. Growth chamber experiments included, additionally, four levels of salinity. Increasing salinity levels caused decreases in most of the parameters evaluated. Low temperature decreased most growth parameters and in combination with salinity acted synergistically to cause a greater detrimental effect. Pesticide treatment decreased most growth parameters, with the exception of root growth. Sweet corn had a greater tolerance to low temperatures and salinity than beans; however, it proved to be more sensitive to pesticide overdoses. These factors in combination had greater detrimental effects on sweet corn percent germination than each factor alone. Suboptimal temperatures reduced percent germination and germination rate, and increased the time to 50% germination. Mgh salinity levels combined with low temperatures acted synergystically on rate and percent germination. Biozyme increased percent germination, but did not hasten germination rate or days to 50% germination. Biozyme treatment of bean seeds helped them overcome pesticide overdose stress. Aerobic respiration was measured 48 h after imbibition. Respiration rate of bean and sweet corn seeds was reduced by pesticide overdose and decreasing temperatures. Respiratory quotient decreased as temperature decreased and increased as pesticide levels increased. Biozyme-decreased bean respiratory quotient and increased sweet corn respiratory quotient. The increase in the respiratory quotient of bean and sweet corn seeds with increasing levels of pesticide suggests an increase in C02 evolution through a pathway that does not increase O2 uptake.