Three main classes of mutations affecting plant height have

been selected:

1. Gibberellin-insensitive dwarfs

2. Gibberellin-deficient mutants in which the gibberellin deficiency has been overcome by a second “suppressor” mutation, so the plants look closer to normal

3. Mutants with a constitutive gibberellin response (“slender” mutants)

TLS Online TPP Program

#Id: 9871

#Unit 6. System Physiology – Plant

The UVR8- COP1-SPA complex then activates the transcription of the major transcription factor HY5, which controls the expression of many of the genes induced by UV-B.

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

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#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.