Cytokinins are defined as compounds that have biological activities similar to those of trans-zeatin. These activities include the ability to do the following:

Induce cell division in callus cells in the presence of an auxin

Promote bud or root formation from callus cultures when in the appropriate molar ratios to auxin

Delay senescence of leaves

Promote expansion of dicot cotyledons

TLS Online TPP Program

#Id: 7147

#Unit 6. System Physiology – Plant

There are three pathways for the synthesis of JAs, including the octadecane pathway starting from α-linolenic acid (18:3) and the hexadecane pathway starting from hexadecatrienoic acid (16:3). 

All three pathways require three reaction sites: the chloroplast, peroxisome, and cytoplasm. 

TLS Online TPP Program

#Id: 7148

#Unit 6. System Physiology – Plant

In plants, mechanical damage or insect feeding can cause rapid and transient accumulation of JA and JA-Ile at the site of injury, thereby activating the expression of defense genes surrounding the wound and producing a local defense response

TLS Online TPP Program

#Id: 7149

#Unit 6. System Physiology – Plant

In the local defense response, there are two ways of short-distance transmission of the JA signal. First, the systemin produced by the wounding acts as a signaling molecule, which is transmitted to the adjacent site through the apoplast and phloem to activate the JA cascade reaction pathway. Second, JA and JA-Ile induced by systemin act as signals and are transported to adjacent sites for defensive responses

TLS Online TPP Program

#Id: 7150

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7151

#Unit 6. System Physiology – Plant

The defense response triggered by a traumatic signal can result in a local defense response near the wound and/or a systemic acquired resistance (SAR) at the uninjured site, and/or even induced defense responses from adjacent plants. 

TLS Online TPP Program

#Id: 7152

#Unit 6. System Physiology – Plant