Jasmonates promote cabbage (Brassica oleracea L. var Capitata L.) root and shoot development

Jasmonates are a new group of plant hormones; their roles on plant development are still little known. The aim of this work is to determine the action of jasmonates on cabbage, Brassica oleracea L. var Capitata, development both in in vitro cultured explants and in whole plants. Jasmonic acid (JA) enhanced nodal explant development when applied at 2–50 nM and inhibited it when supplied at 1250 and 6000 nM JA. Overall plant development was enhanced most under the 10 nM JA treatment; which significantly increased the explant shoot, leaf, and root dry weight. The root system of the explants cultured under the lower JA concentrations appeared more vigorous. Jasmonic acid also promoted the development of isolated in vitro cultured roots when applied at 2 and 10 nM. Root length and weight significantly increased, while concentrations 250 nM JA and over were detrimental. Isolated roots were progressively thicker as the JA concentration increased. Methyl jasmonate promoted both the below- and above-ground cabbage plant development when applied in a confined atmosphere at a concentration of only 1.225 nl.l^–1 MJ: plants were higher and heavier, and showed an improved root system development. On the other hand, the 2.43 nl.l^–1 MJ treatment decreased plant growth. The present work reveals a role for jasmonates as enhancers of in vitro and in vivo cabbage plant development. To our knowledge, no corresponding studies on the effects of jasmonates on whole plants have been previously published.