Effect of Elevated Temperatures on the Activity of Alternative Pathways of Photosynthetic Electron Transport in Intact Barley and Maize Leaves

Effect of Elevated Temperatures on the Activity of Alternative Pathways of Photosynthetic... The light-induced rise in chlorophyll fluorescence and the subsequent decay of fluorescence in darkness were measured in barley and maize leaves exposed to heat treatment. The redox conversions of the photosystem I primary donor P700, induced by far-red light, were also monitored from the absorbance changes at 830 nm. After heating of leaves at temperatures above 40°C, the ratio of variable and maximum fluorescence decreased for leaves of both plant species, indicating the inhibition of photosystem II (PSII) activity. A twofold reduction of this ratio in barley and maize leaves was observed after heating at 45.3 and 48.1°C, respectively, which suggests the higher functional resistance of PSII in maize. The amplitude of the slow phase in the dark relaxation of variable fluorescence did not change after the treatment of barley and maize leaves at temperatures up to 48°C. In leaves treated at 42 and 46°C, the slow phase of dark relaxation deviated from an exponential curve. The relaxation kinetics included a temporary increase in fluorescence to a peak about 1 s after turning off the actinic light. Unlike the slow component, the fast and intermediate phases in the dark relaxation of variable fluorescence disappeared fully or partly after the treatment of leaves at 46°C. The photooxidation of P700 in heat-treated leaves was saturated at much higher irradiances of far-red light than in untreated leaves. At the same time, the dark reduction of P700+ was substantially accelerated after heat treatment. The data provide evidence that the heating of leaves stimulated the alternative pathways of electron transport, i.e., cyclic transport around photosystem I and/or the donation of electrons to the plastoquinone pool from the reduced compounds located in the chloroplast stroma. The rate of alternative electron transport after the heat treatment was higher in maize leaves than in barley leaves. It is supposed that the stimulation of alternative electron transport, associated with proton pumping into the thylakoid, represents a protective mechanism that prevents the photoinhibition of PSII in leaves upon a strong suppression of linear electron transport in chloroplasts exposed to heat treatment. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Plant Physiology Springer Journals

Effect of Elevated Temperatures on the Activity of Alternative Pathways of Photosynthetic Electron Transport in Intact Barley and Maize Leaves

Loading next page...
 
/lp/springer_journal/effect-of-elevated-temperatures-on-the-activity-of-alternative-L3hFuwNHnr
Publisher
Kluwer Academic Publishers-Plenum Publishers
Copyright
Copyright © 2002 by MAIK “Nauka/Interperiodica”
Subject
Life Sciences; Plant Sciences
ISSN
1021-4437
eISSN
1608-3407
D.O.I.
10.1023/A:1020268313852
Publisher site
See Article on Publisher Site

Abstract

The light-induced rise in chlorophyll fluorescence and the subsequent decay of fluorescence in darkness were measured in barley and maize leaves exposed to heat treatment. The redox conversions of the photosystem I primary donor P700, induced by far-red light, were also monitored from the absorbance changes at 830 nm. After heating of leaves at temperatures above 40°C, the ratio of variable and maximum fluorescence decreased for leaves of both plant species, indicating the inhibition of photosystem II (PSII) activity. A twofold reduction of this ratio in barley and maize leaves was observed after heating at 45.3 and 48.1°C, respectively, which suggests the higher functional resistance of PSII in maize. The amplitude of the slow phase in the dark relaxation of variable fluorescence did not change after the treatment of barley and maize leaves at temperatures up to 48°C. In leaves treated at 42 and 46°C, the slow phase of dark relaxation deviated from an exponential curve. The relaxation kinetics included a temporary increase in fluorescence to a peak about 1 s after turning off the actinic light. Unlike the slow component, the fast and intermediate phases in the dark relaxation of variable fluorescence disappeared fully or partly after the treatment of leaves at 46°C. The photooxidation of P700 in heat-treated leaves was saturated at much higher irradiances of far-red light than in untreated leaves. At the same time, the dark reduction of P700+ was substantially accelerated after heat treatment. The data provide evidence that the heating of leaves stimulated the alternative pathways of electron transport, i.e., cyclic transport around photosystem I and/or the donation of electrons to the plastoquinone pool from the reduced compounds located in the chloroplast stroma. The rate of alternative electron transport after the heat treatment was higher in maize leaves than in barley leaves. It is supposed that the stimulation of alternative electron transport, associated with proton pumping into the thylakoid, represents a protective mechanism that prevents the photoinhibition of PSII in leaves upon a strong suppression of linear electron transport in chloroplasts exposed to heat treatment.

Journal

Russian Journal of Plant PhysiologySpringer Journals

Published: Oct 13, 2004

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve Freelancer

DeepDyve Pro

Price
FREE
$49/month

$360/year
Save searches from Google Scholar, PubMed
Create lists to organize your research
Export lists, citations
Access to DeepDyve database
Abstract access only
Unlimited access to over
18 million full-text articles
Print
20 pages/month
PDF Discount
20% off