This document discusses the role of jasmonic acid (JA) and its derivatives as plant growth regulators in horticulture, particularly focusing on their biosynthesis, functions in plant defense, and communication. It highlights the biochemical conversion of linolenic acid to JA and its impact on seed germination and microbial defense mechanisms. Additionally, the document notes the potential applications of JA in agriculture to inhibit pre-harvest seed sprouting.

1. JAVED IQBAL
1st Semester
PhD Horticulture
Plant Growth Regulators
MNS-University of Agriculture, Multan

2. Discovery of JA
 JA’s are derivatives of lipid-based hormone signals that
regulates
 Growth & development, Photosynthesis
 Differentiation i.e. reproductive development
 Plant defense against biotic & abiotic stresses
 Some JA releases as volatile organic compounds (VOCs) for
communication between plants in anticipation of mutual
dangers
 Isolated methyl jasmonate from jasmine oil derived
from Jasminum grandiflorum led to the discovery of the
molecular structure of jasmonates and their name

3. Biosynthesis of Jasmonates
 Jasmonates (JA) are an oxylipin, i.e. a derivative of oxygenated fatty
acid
 Linolenic acid in chloroplast membranes
 Conversion 12-oxo-phytodienoic acid (OPDA)
 Reduction and three rounds of oxidation to form (+)-7-iso-JA, jasmonic
acid
 Only the conversion of linolenic acid to OPDA occurs in
the chloroplast; all subsequent reactions occur in the peroxisome
 JA itself can be further metabolized into active or inactive derivatives.
Methyl JA (MeJA) is a volatile compound that is potentially responsible
for interplant communication
 JA conjugated with amino acid isoleucine (Ile) results in JA-Ile, which
is currently the only known JA derivative needed for JA signaling.
 JA undergoes decarboxylation to give cis-jasmone

4. JA biosynthesis
 Jasmonic acid (JA) is an organic compound found in
several plants
 Molecule is a member of the jasmonate class of plant
hormones
 Biosynthesized from linolenic acid by
the octadecanoid pathway in chloroplasts.

5. Function
 Defense against wounding
 Insects
 Microbial pathogens
 JA acts synergistically with the stress hormone
ethylene

6. α-Linolenic Acid
 (ALA) is an n−3 fatty acid. It is one of two essential
fatty acids (the other being linoleic acid), so called
because they are necessary for health and can,t be
produced within the human body. They must be
acquired through diet.
 ALA is an omega-3 fatty acid found in seeds
(chia, flaxseed, hemp, see also table below), nuts
(notably walnuts), and many common vegetable oils

7. Derivatives
 Jasmonic acid is also converted to a variety of
derivatives including the ester methyl jasmonate
 It is also be conjugated to amino acids in some
biological contexts
 Decarboxylation affords the related fragrance jasmone.

8. Function as germination…?
 There was a reciprocal relationship between MeJA
concentrations applied and seed germination and
radicle growth (Norastehnia, 2003)
 Alphas amylase activity is decreased in the presence of
MeJM
 Reduction in Ethylene production, which is necessary
for seed germination

10. RESEARCHABLE ISSUES
 Vivipary…….
 Pre-harvest seed sprouting
 Wheat
 Rice
 Barley
 Oat
 maize
 China, Japan, Florida efforts to inhibit the pre-harvest
seed sprouting in cereals by exogenous application of
MeJM