Auxin influx 

Auxin can enter plant cells from any direction by either of two mechanisms:

Passive diffusion of the protonated (IAAH) form across the phospholipid bilayer

Secondary active transport of the dissociated (IAA–) form via a 2H+–IAA– symporter

The dual pathway of auxin uptake arises because the passive permeability of the membrane to auxin depends strongly on the apoplastic pH.

TLS Online TPP Program

#Id: 8832

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 8833

#Unit 6. System Physiology – Plant

In plants, various nonphotochemical quenching (NPQ) processes act as safety valves for photosynthesis that dissipate excess absorbed light energy harmlessly as heat

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#Id: 8834

#Unit 6. System Physiology – Plant

Buildup of a acidic thylakoid ΔpH in the presence of excess light resulting the thylakoid lumen activates an enzyme (violaxanthin de‐epoxidase) that converts violaxanthin into zeaxanthin

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#Unit 6. System Physiology – Plant

Protonation of a membrane protein (PSBS) that promotes a dissipative state of LHC proteins in the PSII antenna is also a major form of NPQ

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#Id: 8836

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 8837

#Unit 6. System Physiology – Plant

The ascorbate-glutathione pathway (Halliwell-Asada cycle) is an indispensible component of the ROS homeostasis mechanism of plants.