Long-term water stress leads to acclimation of drought sensitivity of photosynthetic capacity in xeric but not riparian Eucalyptus species

Shuang Xi Zhou*, Belinda E. Medlyn, Iain Colin Prentice

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    47 Citations (Scopus)

    Abstract

    Background and Aims Experimental drought is well documented to induce a decline in photosynthetic capacity. However, if given time to acclimate to low water availability, the photosynthetic responses of plants to low soil moisture content may differ from those found in short-term experiments. This study aims to test whether plants acclimate to long-term water stress by modifying the functional relationships between photosynthetic traits and water stress, and whether species of contrasting habitat differ in their degree of acclimation.

    Methods Three Eucalyptus taxa from xeric and riparian habitats were compared with regard to their gas exchange responses under short- and long-term drought. Photosynthetic parameters were measured after 2 and 4 months of watering treatments, namely field capacity or partial drought. At 4 months, all plants were watered to field capacity, then watering was stopped. Further measurements were made during the subsequent 'drying-down', continuing until stomata were closed.

    Key Results Two months of partial drought consistently reduced assimilation rate, stomatal sensitivity parameters (g1), apparent maximum Rubisco activity (Vcmax′) and maximum electron transport rate (Jmax′). Eucalyptus occidentalis from the xeric habitat showed the smallest decline in Vcmax′ and Jmax′; however, after 4 months, Vcmax′ and Jmax′ had recovered. Species differed in their degree of Vcmax′ acclimation. Eucalyptus occidentalis showed significant acclimation of the pre-dawn leaf water potential at which the Vcmax′ and 'true' Vcmax (accounting for mesophyll conductance) declined most steeply during drying-down.

    Conclusions The findings indicate carbon loss under prolonged drought could be over-estimated without accounting for acclimation. In particular, (1) species from contrasting habitats differed in the magnitude of V′cmax reduction in short-term drought; (2) long-term drought allowed the possibility of acclimation, such that V′cmax reduction was mitigated; (3) xeric species showed a greater degree of V′cmax acclimation; and (4) photosynthetic acclimation involves hydraulic adjustments to reduce water loss while maintaining photosynthesis.

    Original languageEnglish
    Pages (from-to)133-144
    Number of pages12
    JournalAnnals of Botany
    Volume117
    Issue number1
    DOIs
    Publication statusPublished - 1 Jan 2016

    Keywords

    • drought acclimation
    • photosynthesis
    • water stress
    • Vcmax
    • Jmax
    • water use efficiency
    • stomatal conductance
    • mesophyll conductance
    • Huber value
    • hydraulic adjustment
    • riparian Eucalyptus camaldulensis
    • xeric Eucalyptus occidentalis

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