1. Volatile Signals:
When plants are attacked by herbivore, they releases a blend of volatile chemicals that act as distress signal. These volatile include terpens, green leaf volatile and jasmonic acids derivatives. The herbivore-induced volatiles(HVs) diffuse into the air and can be detected by neighboring plants of the same or different species.
HVs can elicit defenses in neighboring plants by activating specific pathways and gene expression involved in defence response. For example, in response to HVs emitted by attacked sagebrush( Artemisia tridentata), nearby sagebrush plants produced elevated levels of defensive chemicals, making them less desirable to herbivores.
2. Elicitors and Hormones:
In addition to volatile, herbivore feeding can trigger the release of damage- associate molecular patterns(DAMPS) and elicitors, such as oligosaccharide and proteins fragments. These elicitors interact with specific receptor on the plant cells membranes, triggering a cascade of defence responses.
One important hormone signal involved in perceiving herbivore attack is jasmonic acid (JA). JA is produced upon herbivore feeding and plays crucial role in mediating defence response. It regulates the production of defensive compounds, such a protease inhibitors and secondary metabolite that deter or poison herbivores.
3. Mechanical Damage and Touch Response:
Plants can also respond to the mechanical damage caused by herbivores chewing on their tissues. Specialized mechanoreceptors on plant cell membranes and tissues sense this mechanical stimuli and initiate defensive response.
For instance, the Venus flytrap( Dionaea muscipula) rapidly snaps its leaves shut upon sensing the touch of potential preys, trapping the insect inside. This touch-sensitive mechanism allows the plant to capture and digest insects, supplementing its nutrient acquisition.
4. Inducible Resistance:
Plants ability to perceive and respond to herbivore attack can be enhanced through processes known as inducible resistance. When a plant experiences herbivore damage or exposure to elicitors, it can develop a memory of the attack and become more resistance to subsequent attacks.
This inducible resistance involves changes in gene expression and metabolism that strengthen plant defense and result in faster and stronger response when challenged again by herbivore.
Conclusion:
Plants have developed intricate mechanisms to sense herbivore attack, which involve perceiving volatile signals, elicitors, and mechanical damage. These cues initiate a range of defense response like producing deterrent chemicals, activating hormone signalling pathways, and enhancing resistance to future attack. By understanding how plants perceive predators, scientist can gain insights into developing strategies for sustainable pest management and improving crop protection.
