Hyperactivation mediated by the opening of the sperm specific calcium channels, the CatSper proteins, in the sperm tail.

TLS Online TPP Program

#Id: 4968

#Unit 6. System Physiology – Plant

Very Low Fluence (VLF) Responses

It sensitive to low levels of light (0.1 nmol m -2 . Less than 0.02% is Pfr). These are not photo-reversible and saturate at 50 nmol m -2 . Some examples include;

a) mesocotyl elongation in cereals; and 

b) Arabidopsis seed germination

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)