Effect of two forms of maleic hydrazide on the cell structure at the midsection,stem and bud ends of the cortical and perimedullary regions of Russet Burbank tubers

The cortical and perimedullary cells of the potato tuber increased in size when treated with the diethanolamine and the potassium salt of maleic hydrazide. The best time for maleic hydrazide application appeared to be from mid to late July. There was a greater increase in cell size in the cortex than the perimedullary region and treatment with the amine salt was more effective than the potassium salt. The cells were smallest at the bud end; however, with maleic hydrazide treatment, increase in cell size was greater in this region compared to the midsection and stem end. From late August to late September the cell size of untreated tubers remained relatively unchanged, whereas, tubers treated with the amine salt showed a 16 to 46% increase with a lesser increase with the potassium salt. The rounder form of the treated tubers can be explained by the shape and increase in cell size in the cortical and perimedullary region. Increase in cell size also may help prevent the formation of misshapen tubers.