University of Tasmania
Browse
Oecol__conifer__light.pdf (419.44 kB)

Light response characteristics of a morphologically diverse group of southern hemisphere conifers as measured by chlorophyll fluorescence

Download (419.44 kB)
journal contribution
posted on 2023-05-16, 10:29 authored by Timothy BrodribbTimothy Brodribb, Robert HillRobert Hill
Unlike northern hemisphere conifer families, the southern family. Podocarpaceae, produces a great variety of foliage forms ranging from functionally broad-, to needle-leaved. The production of broad photosynthetic surfaces in podocarps has been linked qualitatively to low-light-environments, and we undertook to assess the validity of this assumption by measuring the light response of a morphologically diverse group of podocarps. The light response, as apparent photochemical electron transport rate (ETR), was measured by modulated fluorescence in ten species of this family and six associated species (including five Cupressaceae and one functionally needle-leaved angiosperm) all grown under identical glasshouse conditions. In all species, ETR was found to increase as light intensity increased, reaching a peak value (ETR(max)) at saturating quantum flux (PPFD(sat)), and decreasing thereafter. ETR(max) ranged from 217 μmol electrons m-2 · s-1 at a PPFD(sat) of 1725 μmol photons m-2 · s-1 in Actinostrobus acuminatus to an FTR of 60 μmol electrons · m-2 · s-1 at a PPFD(sat) of 745 μmol electrons · m-2 · s-1 in Podocarpus dispermis. Good correlations were observed between ETR(max) and both PPFD(sat) and maximum assimilation rate measured by gas-exchange analysis. The effective quantum yield at light saturation remained constant in all species with an average value of 0.278 ± 0.0035 determined for all 16 species. Differences in the shapes of light response curves were related to differences in the response of non-photochemical quenching (q(n)), with q(n) saturating faster in species with low PPFD(sat). Among the species of Podocarpaceae, the log of average shoot width was well correlate with PPFD(sat), wider leaves saturating at lower light intensities. This suggests that broadly flattened shoots in the Podocarpaceae are an adaptation to low light intensity.

History

Publication title

Oecologia

Volume

110

Pagination

10-17

ISSN

0029-8549

Department/School

School of Natural Sciences

Publisher

Springer-Verlag

Place of publication

Netherlands

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the environmental sciences

Usage metrics

    University Of Tasmania

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC