The amino acids for which the Class I synthetases are specific tend to be larger and more hydrophobic than those for Class II synthetases.

TLS Online TPP Program

#Id: 10125

#Unit 6. System Physiology – Plant

H+–IAA– symporter cotransports two protons along with

the auxin anion which changes pH 7 equilibrium of cytosol so H+ ATPase actively transports H+ in apoplast

TLS Online TPP Program

#Id: 10126

#Unit 6. System Physiology – Plant

Auxin always exits cells as IAA- anions via auxin anion efflux carriers that are concentrated at the basal ends of each cell in the longitudinal pathway.

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