Growth and Development of Horticultural Crops (1+1)

2. Jasmonic acid

• Jasmonic acid (JA), is a cyclopentanone derivatives synthesized from linolenic acid via the octadecanoic pathway. It acts as a growth inhibitor and seems to participate in leaf senescence and in the defense mechanism against fungi.
• Jasmonate derivatives induce the accumulation of so-called jasmonate-induced-proteins that were found in all plant species tested. Their accumulation can also be caused by desiccation or ABA effects.
• Jasmonate-induced-proteins are lacking in roots, in bleached leaves, and in leaves of chlorophyll-deficient Hordeum vulgare mutants.
• They exist in etiolated leaves, though Jasmonates do not only regulate the transcription of these proteins, they do also influence the rate of translation of different groups of mRNA.
• They do, for example, decrease the production rate of several essential housekeeping proteins. Just like ABA, jasmonates also inhibit premature germination of the oil-containing seeds of Brassica and Linum. After germination, they do induce the synthesis of the seed storage proteins Napin and Cruciferin as well as that of several more elaiosome-associated proteins.
Influence in fruit culture

• n-Propyl dihydrojasmonate (PDJ) treatment at 91 days after full bloom (DAFB) decreased endogenous ABA and its metabolite but increased ethylene concentration and hence increased fruit ripening of mangoes (Kondog et al., 2004)
• Methyl jasmonate treatments increased ethylene production at the climacteric stage and was more pronounced at a higher concentration (10^-3M) of applied methyl jasmonate. Skin colour of ripe fruit was significantly improved with exogenous application of methyl jasmonate (10^-3M). Methyl jasmonate treatments also increased the concentration of fatty acids as well as total aroma volatiles, monoterpenes, sesquiterpenes, aromatics, norisoprenoid, alcohols and esters in the pulp of fruit. However, exogenous application of methyl jasmonate tended to reduce production of n-tetradecane, especially on day 5 and 7 of ripening. In general, exogenous application of methyl jasmonate (10^-3M) significantly promoted biosynthesis of ethylene, fatty acids and ripening and aroma volatile compounds during fruit ripening. Our experimental results suggest that methyl jasmonte is involved in early steps in the modulation of mango fruit ripening (Lalel et al., 2003).
• Raspberries treated with MJ had higher soluble solids content, total sugars, fructose, glucose, sucrose and lower titratable acids (TAs), malic acid and citric acid than untreated fruit. MJ also significantly enhanced the content of flavonoids and the antioxidant capacities in the fruit (Wang et al., 2005).