All-or-none action potentials

the minimal intensity of stimulating current (threshold intensity) that, acting for a given duration, will just produce an action potential. The thresholdintensity varies with the duration; with weak stimuli it is long, and with strong stimuli it is short

TLS Online TPP Program

#Id: 9851

#Unit 6. System Physiology – Plant

Both phytochromes and cryptochromes entrain the circadian clock in Arabidopsis.

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#Id: 9852

#Unit 6. System Physiology – Plant

Blue light depolarizes membrane of hypocotyl cells and inhibits of growth rate.

This membrane depolarization is caused by the activation of anion channels, which facilitates the efflux of anions such as chloride.

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#Id: 9853

#Unit 6. System Physiology – Plant

an anion channel blocker, NPPB (5-nitro-2-[4-phenylbutylamino]- benzoate), prevents the blue light–dependent membrane depolarization and decreases the inhibitory effect of blue light on hypocotyl elongation.

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#Id: 9854

#Unit 6. System Physiology – Plant

Phototropins (phots) are involved in directing organ, chloroplast, and nuclear movements, solar tracking, and stomatal opening

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#Id: 9855

#Unit 6. System Physiology – Plant

In Mougeotia, the photoreceptors regulating chloroplast movement consist of a fusion between phytochrome and a phototropin known as neochrome, and show typical bilin binding as well as red/far-red reversibility.

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#Id: 9856

#Unit 6. System Physiology – Plant

Mougeotia appears to have evolved the ability to exploit red light as a signal to induce a response (chloroplast movement) that is typically mediated by blue light.