Sperm rheotaxis 

migrate against the direction of the flow—using

CatSper calcium channels (like sea urchin sperm) to sense calcium influx and monitor the direction of the

current

TLS Online TPP Program

#Id: 10127

#Unit 6. System Physiology – Plant

Polar auxin transport is described in terms of the direction of its movement in relation to the base of the plant (the root–shoot junction). 

TLS Online TPP Program

#Id: 10128

#Unit 6. System Physiology – Plant

Auxin moving downward from the shoot moves basipetally (toward the base) until it reaches the root–shoot junction.

TLS Online TPP Program

#Id: 10129

#Unit 6. System Physiology – Plant

From that point, downward movement is described as acropetal (toward the apex). Movement of auxin from the apex of the root toward the root–shoot junction is also described as basipetal (toward the base).

TLS Online TPP Program

#Id: 10130

#Unit 6. System Physiology – Plant

PIN and ABCB transport proteins direct the auxin efflux component of polar auxin transport throughout the plant

TLS Online TPP Program

#Id: 10131

#Unit 6. System Physiology – Plant

PIN1 mediates vertical transport of IAA from the shoot to the root along the embryonic apical–basal axis and creates an auxin sink that drives basipetal auxin transport upward from the root apex via PIN2 efflux carriers.

TLS Online TPP Program

#Id: 10132

#Unit 6. System Physiology – Plant

PIN7 and PIN3 are thought to redirect auxin back into vascular parenchymal tissue, where polar transport takes place.