Plants defences against pathogens

What is a passive mechanism?

Present all the time

What are the physical barriers of a Plant

– Waxy cuticle overleaf epidermis

– Bark

– Cellulose cell walls

– Casparian strip in Endodermis of root

– Tomato close to stop entry of pathogens

What are the chemical defences of a plant?

– Secretion of compounds to support growth of microorganisms that compete with pathogens

– Secretion of compounds Toxic to pathogens

– Secretion of inhibitors of enzymes, e.g. cellulose used by pathogens to breakdown cell walls to gain entry to cells

– Receptor molecules on cell surface membranes that detect pathogens and activate plant defences

– Sticky resin in bark that prevents spread of pathogens

What is Callose?

A polysaccharide that has 1,3 like acidic bonds and some 1,6 Glycolic bonds

Why is callose made?

It is made by plant cells in defence against attack by pests and pathogens to blocks pores and phloem tubes, reduce width of plasmodesmata and thickening the cell walls. Reduces spread of viruses from cell cell

Where is callose Deposited

Between cell surface membrane and cell wall

What is phytoalexins?

They are defence chemicals that act in a variety of different ways. They:

– Disrupt cell surface membrane of bacteria

– Stimulates secretion of chitinases that breakdown cell walls of hyphae of fungal pathogen

– Disrupt metabolism of pathogens

– Delay reproduction of pathogens