MCQ IN MEDICINE

Detailed explanation-1: -Constitutive (continuous) defenses include many preformed barriers such as cell walls, waxy epidermal cuticles, and bark. These substances not only protect the plant from invasion, they also give the plant strength and rigidity.

Detailed explanation-2: -Sclerophylly refers to the hardened leaves, and plays an active role in plant defense against herbivores by reducing the palatability and digestibility of the tissues, thereby, reducing the herbivore damage. Spinescence includes plant structures such as spines, thorns and prickles.

Detailed explanation-3: -Physical defences Each plant cell has a cellulose cell wall which acts as another barrier against infection.

Detailed explanation-4: -Defence mechanisms comprise properties of the host that decrease this damage. The mechanisms are passive when they are independent of the pathogen. They are active when they follow changes in the host caused by the pathogen.

Detailed explanation-5: -defence response by secreting metabolic toxins. Even after the establishment of infection in plant cells, the host defence system tries to create barriers for further colonization of tissues. This may be at various levels. In several plants the infected cells are surrounded by suberized cells.