In addition to the fluence, some phytochrome responses are sensitive to the irradiance, 2 or fluence rate, of light. The units of irradiance in terms of photons are moles of quanta per square meter per second (mol m–2 s–1).

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#Unit 6. System Physiology – Plant

Root hair cellular responses to bacterial Nod factor

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#Unit 6. System Physiology – Plant

Plant genes expressed early, or in the absence of bacterial infection, are termed “early nodulins” or ENOD

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#Unit 6. System Physiology – Plant

Three factors are important in maintaining low O2 concentrations in nodules. 

First, entry of O2 into the nodule is controlled by a variable‐permeability barrier in the nodule parenchyma

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#Unit 6. System Physiology – Plant

O2‐binding plant protein Lb plays an active role in regulating and delivering O2 in the infected cells

Bacterial respiration is the major O2 sink

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#Unit 6. System Physiology – Plant

O2‐sensitive hemoprotein kinase FixL controls a regulatory cascade that activates transcription of nitrogen fixation genes

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#Unit 6. System Physiology – Plant

Plant glutamine synthetase (GS) and NADH‐dependent glutamate synthase (NADH‐GOGAT) are responsible for the initial massimilation of ammonia into organic compounds