The physiological effects of the seed treatment Stamina on maize seedling length, ADP:O ratios, and respiration rates
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Zea mays L. is an important crop in the Midwest, and each year there is a push to plant earlier in the spring. Early planting can leave seeds and seedlings vulnerable to low temperature stress. Low temperature stress causes damage to maize seedlings. It has been postulated that Strobilurin fungicides have positive physiological related effects on growth and yield. The goal of this study was to determine if the strobilurin Stamina protects maize seedlings against mitochondrial damage due to low temperature stress. In this study, three seed treatments and two seed lots/hybrids were used. Treatments included: Stamina (binders plus active ingredients), binders only, and control (untreated) seedlings. To determine the effects of Stamina on maize respiration, seedling lengths, ADP:O ratios, respiration rates, and alternative oxidase (appendix) were measured under optimal temperature and low temperature conditions in the presence and absence of the alternative oxidase inhibitor salicylhydroxamic acid (SHAM). Seedlings were grown in dark growth chambers at a constant 25°C for 5 days or for 10 days at 10°C and 4 days at 25°C. In the optimal temperature study, seedlings from Stamina and only binders treated seeds had mesocotyl lengths that were 0.48 cm and 0.41 cm longer than control seeds, respectively. Seedlings from Stamina treated seeds had total lengths that were 0.38 cm and 0.87 cm longer than seeds treated with binders only and control seedlings, respectively. Stamina had no effect on ADP:O ratios, AOX ratios, respiration rates, or respiration rate ratios. In the low temperature stress study, there was a hybrid by treatment interaction. Stamina did not affect seedling length of seed lot/hybrid A, but it did of seed lot/hybrid B. Seedlings from Stamina treated seeds of seed lot/hybrid B had mesocotyl lengths that were 0.9 cm longer than both seedlings treated with only binders and control seedlings. Seedlings from Stamina treated seeds of the same seed lot/hybrid had total lengths that were 1.16 cm and 1.21 cm longer than seedlings treated with only binders and control seedlings, respectively. Seedlings from Stamina treated seeds and control seedlings had AOX ratios that were slightly larger than AOX ratios for seedlings treated with only binder when 20 mM SHAM was used. Seedlings from Stamina treated seeds and control seedling of seed lot/hybrid A had slightly larger respiration rate ratios than seedlings from seeds treated with only binders when 10 mM SHAM was used. Seedlings from Stamina treated seeds had slightly larger respiration rate ratios than control seedlings of seed lot/hybrid B when 10 mM SHAM was used.