Journal Article

Thermal energy dissipation and its components in two developmental stages of a shade-tolerant species, <i>Nothofagus nitida</i>, and a shade-intolerant species, <i>Nothofagus dombeyi</i>

Marjorie Reyes-Díaz, Alexander G. Ivanov, Norman P.A. Huner, Miren Alberdi, Luis J. Corcuera and León A. Bravo

in Tree Physiology

Volume 29, issue 5, pages 651-662
Published in print May 2009 | ISSN: 0829-318X
Published online May 2009 | e-ISSN: 1758-4469 | DOI:
Thermal energy dissipation and its components in two developmental stages of a shade-tolerant species, Nothofagus nitida, and a shade-intolerant species, Nothofagus dombeyi

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Nothofagus dombeyi (Mirb.) Blume and Nothofagus nitida (Phil.) Krasser, two evergreens in the South Chilean forest, regenerate in open habitats and under the canopy, respectively. Both overtop the forest canopy when they are in the adult stage, suggesting that their photoprotective mechanisms differ in ontogenetic dynamics. We postulated that N. nitida, a shade-tolerant species increases its capacity to tolerate photoinhibitory conditions (low temperature and high irradiance) by thermal energy dissipation of excess energy during its transition from the seedling to the adult stage, whereas N. dombeyi, a shade-intolerant species, maintains a high capacity for photoprotection by thermal energy dissipation from the seedling to the adult stage. To test this hypothesis, the main photoprotective mechanisms in plants – the fast- and slow-relaxing components of thermal energy dissipation (NPQ, non-photochemical quenching) NPQF and NPQS, respectively, and state transitions – were studied in seedlings and adults of both species grown in their natural habitats and in a common garden. In adults, NPQF and NPQS did not differ between species and seasons. The greatest differences in these parameters were observed in seedlings. The xanthophyll cycle was more active in N. dombeyi seedlings than in N. nitida seedlings at low temperature and high irradiance, consistent with a higher NPQF in N. dombeyi. Under all study conditions, N. nitida seedlings had higher NPQS than N. dombeyi seedlings. The state transition capability was higher in N. nitida seedlings than in N. dombeyi seedlings. Therefore, although (shade-intolerant) N. dombeyi was able to thermally dissipate the excess absorbed energy, under natural conditions its photochemical energy quenching was efficient in both developmental stages, decreasing its need for thermal dissipation. In contrast, the seedlings of N. nitida were more sensitive to photoinhibition than the adult trees, suggesting a change from shade-grown to sun-exposed phenotype from the seedling to the adult stage. These results help to explain the differences in the regeneration patterns of N. nitida and N. dombeyi and the presence of N. nitida adult stage in the upper canopy.

Keywords: non-photochemical quenching; ontogeny; photosystem II; state transitions; xanthophyll cycle

Journal Article.  7276 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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