JASMONIC ACID DISTRIBUTION AND ACTION IN PLANTS - REGULATION DURING DEVELOPMENT AND RESPONSE TO BIOTIC AND ABIOTIC STRESS

Jasmonic acid (JA) is a naturally occurring growth regulator found in higher plants, Several physiological roles have been described for thi s compound (or a related compound, methyl jasmonate) during plant deve lopment and in response to biotic and abiotic stress, To accurately de termine JA levels in plant tissue, we have synthesized JA containing C -13 for use as an internal standard with an isotopic composition of [2 25]:[224] 0.98:0.02 compared with [225]:[224] 0.15:0.85 for natural ma terial, GC analysis (flame ionization detection and MS) indicate that the internal standard is composed of 92% 2-(+/-)-[C-13]JA and 8% 2-(+/ -)-7-iso-[C-13]JA. In soybean plants, JA levels were highest in young leaves, flowers, and fruit (highest in the pericarp). In soybean seeds and seedlings, JA levels were highest in the youngest organs includin g the hypocotyl hook, plumule, and 12-h axis, In soybean leaves that h ad been dehydrated to cause a 15% decrease in fresh weight, JA levels increased approximate to 5-fold within 2 h and declined to approximate ly control levels by 4 h, In contrast, a lag time of 1-2 h occurred be fore abscisic acid accumulation reached a maximum, These results will be discussed in the context of multiple pathways for JA biosynthesis a nd the role of JA in plant development and responses to environmental signals.