Monocot leaf (Isobilateral leaf) 

Epidermis ;

Consists of upper and lower epidermis.

Both the layers are cutinized.

In some grasses they are large with thin, flexible walled cells called as Motor or Bulliform cells

Mesophyll ;

Not differentiated into palisade and spongy.

Made of parenchyma cells which have Chloroplasts.

Vasular bundle

Arranged in parallel manner.

Conjoint, Collateral and Closed and enclosed by a bundle sheath Xylem (adaxial) and Phloem (abaxial)

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Four major pathogens infects plants most frequently

1. Viruses

2. Bacteria

3. Fungi

4. Insects

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Late blight disease (A), caused by the oomycete pathogen Phytophthora infestans

Black stem rust, which results from infection by the basidiomycete Puccinia graminis

Global banana (Musa spp.) production is under threat from black Sigatoka disease Mycosphaerella fijiensis.

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An effector molecule is

made by a pathogen to enhance the pathogen’s colonizing

abilities.

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Plant pathogens are divided into three groups

Biotrophs derive energy from living cells, they are found on or in living plants, can have very complex nutrient requirements and do not kill host plants rapidly;

Necrotrophs derive energy from killed cells; they invade and kill plant tissue rapidly and then live saprotrophically on the dead remains;

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Hemibiotrophs have an initial period of biotrophy followed by necrotrophy.

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Biotrophs are Specialised (‘obligate’) pathogens

Possess appressoria or haustoria

Narrow host range

Controlled by salicylate-dependent host-defence pathways