For a “sun plant” or “shade-avoiding plant” there is a clear adaptive value in allocating its resources toward more rapid extension growth when it is shaded by another plant.

TLS Online TPP Program

#Id: 9721

#Unit 6. System Physiology – Plant

Plant immunity involves

Anatomical/Mechanical Barriers & Constitutive Immunity

Inducible Défense

TLS Online TPP Program

#Id: 9722

#Unit 6. System Physiology – Plant

Thorns are modified branches, as in citrus and acacia; spines

are modified leaves

Prickles are derived mainly from the epidermis and thus can be easily snapped off the stem, protect plants from larger herbivores

Trichomes, or hairs, provide a much more effective defense against insect pests

TLS Online TPP Program

#Id: 9723

#Unit 6. System Physiology – Plant

Trichomes of nettles (Urtica dioica) have “cocktail” of secondary metabolites that can cause severe irritation of the skin of animals.

TLS Online TPP Program

#Id: 9724

#Unit 6. System Physiology – Plant

Calcium oxalate crystals are present in the vacuoles of many species, and may be distributed evenly throughout the leaf or restricted to specialized cells called idioblasts

TLS Online TPP Program

#Id: 9725

#Unit 6. System Physiology – Plant

Constitutive chemical defenses are effective against many different herbivores, including insects and mammals. 

TLS Online TPP Program

#Id: 9726

#Unit 6. System Physiology – Plant

Hemlock (Cicuta sp.) produces cicutoxin, a polyacetylene that prolongs the repolarization of neuronal action potentials.