Nitric oxide stimulates seed germination and de-etiolation, and inhibits hypocotyl elongation, three light-inducible responses in plants |
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Authors: | María Verónica Beligni Lorenzo Lamattina |
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Institution: | (1) Instituto de Investigaciones Biológicas (IIB), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, 7600 Mar del Plata, Argentina, AR |
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Abstract: | Seed germination, greening of etiolated plants and inhibition of hypocotyl elongation are stimulated by light, which is sensed
by various types of photoreceptor. Nitric oxide (NO) has proven to be a bioactive molecule, especially in mammalian cells
and, most recently, in plants. Like some phytochrome-dependent processes, many NO-mediated ones are accomplished through increases
in cGMP levels. Given these similarities, we proposed that NO could take part in light-mediated events in plants. Here we
show that NO promotes seed germination and de-etiolation, and inhibits hypocotyl and internode elongation, processes mediated
by light. Two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine induced germination of lettuce (Lactuca sativa L. cv. Grand Rapids) seeds in conditions in which this process is dependent on light (e.g. 26 °C). This was a dose-dependent
response and was arrested by addition of an NO scavenger, carboxy-PTIO. In addition, nitrite and nitrate, two NO-decomposition
products were ineffective in stimulating germination. Wheat seedlings sprayed with SNP and grown in darkness contained 30–40%
more chlorophyll than control seedlings. Nitric-oxide-mediated partial greening was increased by light pulses, wounding and
biotic stress. Arabidopsis thaliana (L.) Heynh. (ecotype Columbia) and lettuce seedlings grown in the dark had 20%-shorter hypocotyls in NO treatments than in
control ones. On the other hand, internode lengths of potato plants growing under low light intensity and sprayed with 100 μM
SNP were also 20% shorter than control ones. These results implicate NO as a stimulator molecule in plant photomorphogenesis,
either dependent on or independent of plant photoreceptors.
Received: 27 April 1999 / Accepted: 16 June 1999 |
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Keywords: | : De-etiolation – Hypocotyl elongation – Light response – Nitric oxide – Photoreceptor – Seed germination |
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