The Forces of Evolution: 

TLS Online TPP Program

#Id: 4970

#Unit 6. System Physiology – Plant

High fluence (HF) or High Irradiance Response (HIR) 

Prolonged or continuous light (10 mmol m -2 ),

fluence rate is important and not fully photoreversible.

TLS Online TPP Program

#Id: 4972

#Unit 6. System Physiology – Plant

Examples of phenomena involved in this High Irradiance Response (HIR) include: 

• anthocyanin synthesis in seedlings and apple skins

• inhibition of hypocotyl elongation in mustard, lettuce and petunia

• plume hook opening in lettuce

• cotyledon enlargement in lettuce

• ethylene production in sorghum

TLS Online TPP Program

#Id: 4974

#Unit 6. System Physiology – Plant

LFR action spectra for the photoreversible stimulation and inhibition of seed germination in Arabidopsis.

TLS Online TPP Program

#Id: 4976

#Unit 6. System Physiology – Plant

Plant photomorphogenic responses induced by high irradiances,

TLS Online TPP Program

#Id: 4978

#Unit 6. System Physiology – Plant

Comparison between the very-low-fluence (VLFR), low-fluence (LFR), and high-irradiance responses (HIR)

TLS Online TPP Program

#Id: 4982

#Unit 6. System Physiology – Plant

HIR action spectrum for the inhibition of hypocotyl elongation of dark-grown lettuce seedlings. The peaks of activity for the inhibition of hypocotyl elongation occur in the UV-A, blue, and far-red regions of the spectrum.