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Photochemistry, energy dissipation and cold-hardening in Eucalyptus nitens and E. pauciflora

journal contribution
posted on 2023-05-16, 11:24 authored by Mark HovendenMark Hovenden, Warren, CR
The allocation of absorbed photon energy to thermal energy dissipation and photosynthetic electron transport was investigated as a function of photosynthetic photon flux density (PPFD) and temperature in two species of subalpine eucalypt, Eucalyptus nitens (Deane et Maiden) Maiden and E. pauciflora Sieb. ex Spreng. The proportion of absorbed light utilised in photosynthetic electron transport decreased with increasing PPFD, and the decrease was more pronounced the lower the temperature. The proportion diverted into dissipation processes increased with increasing PPFD to a maximum where it reached a plateau. This maximum increased with decreasing temperature. Exposure to a succession of cold (4°C) nights increased the photochemical quantum yield of photosystem II and decreased the allocation of excitation energy to thermal dissipation processes in conditions of excess light, particularly at low temperatures. Consequently, the photosynthetic electron transport rate (ETR) was higher and heat dissipation rate (HDR) was lower in hardened plants than in non-hardened plants at low temperatures. At 20°C, ETR was generally higher than HDR in all plants, but as the temperature decreased, HDR became the dominant process. The PPFD at which HDR exceeded ETR decreased with decreasing temperature, and at low temperatures was always lower in non-hardened plants than hardened plants, although quite similar between species.

History

Publication title

Australian Journal of Plant Physiology

Volume

25

Issue

5

Pagination

581-589

ISSN

0310-7841

Department/School

School of Natural Sciences

Publisher

CSIRO

Place of publication

Melbourne

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the environmental sciences

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    University Of Tasmania

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