Large quantities of positive potassium ions diffuse out of the SA node.

TLS Online TPP Program

#Id: 9824

#Unit 6. System Physiology – Plant

Plants that increase stem extension in response to shading are said to exhibit a shade avoidance response.

As shading increases, the R:FR ratio decreases. Shade means far red light

TLS Online TPP Program

#Id: 9825

#Unit 6. System Physiology – Plant

phyB–phyE, appear mostly light-stable in the plant and function primarily in the regulation of LFRs and of shade avoidance involving changes in the R:FR ratio.

TLS Online TPP Program

#Id: 9826

#Unit 6. System Physiology – Plant

phyA is rapidly degraded as Pfr and controls plant responses to VLFRs and the far-red HIRs.

TLS Online TPP Program

#Id: 9827

#Unit 6. System Physiology – Plant

Mutants lacking phyA also failed to germinate in response to millisecond pulses of light, but showed a normal response to red light in the low-fluence range. Means pfr primarily receives VLFR

TLS Online TPP Program

#Id: 9828

#Unit 6. System Physiology – Plant

phyC, phyD, and phyE appear to play roles that are for the most part redundant with those of phyA and phyB. Whereas phyB appears to be involved in regulating all stages of development

TLS Online TPP Program

#Id: 9829

#Unit 6. System Physiology – Plant

The phyB mutants are deficient in chlorophyll

phyB also appears to regulate LFRs, such as photoreversible seed germination

Mutants that lack phyA respond normally to red light, whereas mutants deficient in phyB are unable to respond to low-fluence red light