Endogenous jasmonic acid and radial cell expansion in buds of potato tubers

The finding of the expansion-inducing activity of jasmonic acid and methyl jasmonic acid in medullary tissue of potato tuber, in addition to the occurrence of jasmonic acid in tuber buds and periderms, led us to investigate the possibility of a similar activity during the tuber buds growth. The aim of the present work was to measure the endogenous level of jasmonic acid in buds excised from tubers during two development stages (unsprouted buds and sprouts of 1 cm length) and to study the effect of exogenous jasmonic acid on fundamental meristem cell expansion of tuber excised buds (Solanum tuberosum L. cv. Spunta). Jasmonic acid endogenous level in tubers with unsprouted buds was 325 ng g(-1) dry weight, diminishing during sprouting to 164 ng. In excised buds exposed to different concentrations of jasmonic acid the corpus cells responded to all treatments increasing radial cell expansion; the highest mean value (178.03 mu m) was obtained with jasmonic acid 3 x 10(-8) mel L-1. The high levels of jasmonic acid found in potato tuber buds in correlation with the capacity of this compound to induce radial expansion of the meristematic cells in the buds indicate the participation of jasmonic acid in the growth of these organs during the process of bud transformation into sprouts.