Tree tissue formation under low temperature stress

• Forschungsstelle: COST
• Projektnummer: C12.0085
• Projekttitel Englisch: Tree tissue formation under low temperature stress

Schlüsselwörter (Englisch)

cold stress; root growth; cell anatomy; cell-wall composition; trees; meristem; low temperatures

Forschungsprogramme (Englisch)

COST-Action FP1106 - STReESS - Studying Tree Responses to extreme Events: a SynthesiS

Kurzbeschreibung (Englisch)

Low temperature stress constrains tree growth, but the underlying mechanisms are unresolved. Since it became obvious that cold stress does not invoke carbon limitation, but exerts direct impacts on meristems, stress research refocused toward understanding the physiological impact of low temperature on tissue formation. Similar cold-limits for growth were previously shown across temperate tree species, but the cold temperature impact on cellular processes are largely unknown. We aim to decipher these processes by experimental studies and surveys across natural climatic transects. All meristematic and cambial activity should be controlled by similar basic mechanisms, but for practical reasons we will focus on root growth as a proxy, and use anatomical and biochemical methods to identify the main driver behind the low temperature growth cessation. We will address this topic within three separate work packages: 1) an assessment of morphology, cell anatomy and cell-wall composition of roots from different tree species experimentally produced at their cold-temperature limit, 2) a sequential root-cooling and -warming experiment to identify key-processes of low temperature stress, 3) a survey of morphology and cell-wall composition of tree roots across sharp, natural soil temperature gradients. This project will offer a mechanistic explanation of low temperature stress on tree tissue growth and largely contribute to the general understanding of tree growth under cold stress.

Partner und Internationale Organisationen (Englisch)

AT; BE; BA; BG; HR; CZ; DK; EE; FI; FR; DE; EL; HU; IS; IE; IL; IT; LU; NL; NO; PL; PT; RO; RS; SK; SI; ES; SE; TR; UK

Abstract (Englisch)

The work proceeded on schedule an was conducted by two part-time postdocs. The work was completed by 30 April 2016. Low temperature stress constrains tree growth, but the underlying mechanisms are unresolved. Since it became obvious that cold stress does not invoke carbon limitation, but exerts direct impacts on meristems, stress research refocused toward understanding the physiological impact of low temperature on tissue formation. Similar cold-limits for growth were previously shown across temperate tree species, but the cold temperature impact on cellular processes are largely unknown. All meristematic and cambial activity should be controlled by similar basic mechanisms, but for practical reasons we focussed on root growth as a proxy. We used anatomical, biochemical and phenotyping methods to identify the main drivers behind the low temperature limit of tissue formation. We hypothesised that lignin formation will be limited by low temperatures, since algae and non-lignified plants can still produce tissue at cold temperature. We addressed this topic within two separate work packages: 1) an assessment of morphology, cell anatomy and cell-wall composition of roots from different tree species experimentally produced at their cold-temperature limit, 2) a sequential root-cooling and -warming experiment to identify key-processes of low temperature stress. Chemical and microscopic observation of tissues formed at cold temperatures revealed – contrary to our expectations – that lignification is not limited by low temperature. It rather appears that cell wall formation per se is limited. Tissues formed under low temperature stress had a smaller proportion of cell wall per dry matter. Further, the balance between cellulose and hemicellulose changed at low temperature, with less cellulose and more hemicellulose under cold temperature stress. These results are independent of tissue type, and were found in roots as well as stem tissue of two independent experiments. The sequential root-cooling and –warming experiment revealed a close coupling of growth rates to temperature and a fast response of root growth rates to changes in temperature. Our data indicates, that not only the degree of temperature stress but also it’s duration affects plant growth. Even short term spells of high temperature could possibly be used to increase the tissue quality of plants growing under low temperature stress These results suggest a direct impact of low temperature on the formation of cell walls. We can only speculate about the exact mechanisms behind this limitation. However, these results have a fundamental impact on our understanding of plant performance under low temperature stress. With the knowledge gained in this project, we can support the hypothesis of low temperature limitation of tissue formation as the main driver of global treeline positions.

Datenbankreferenzen (Englisch)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C12.0085