Journal Article

Root signals and stomatal closure in relation to photosynthesis, chlorophyll <i>a</i> fluorescence and adventitious rooting of flooded tomato plants

Mark A. Else, Franciszek Janowiak, Christopher J. Atkinson and Michael B. Jackson

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 103, issue 2, pages 313-323
Published in print January 2009 | ISSN: 0305-7364
Published online November 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn208
Root signals and stomatal closure in relation to photosynthesis, chlorophyll a fluorescence and adventitious rooting of flooded tomato plants

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

An investigation was carried out to determine whether stomatal closure in flooded tomato plants (Solanum lycopersicum) results from decreased leaf water potentials (ψL), decreased photosynthetic capacity and attendant increases in internal CO2 (Ci) or from losses of root function such as cytokinin and gibberellin export.

Methods

Pot-grown plants were flooded when 1 month old. Leaf conductance was measured by diffusion porometry, the efficiency of photosystem II (PSII) was estimated by fluorimetry, and infrared gas analysis was used to determine Ci and related parameters.

Key Results

Flooding starting in the morning closed the stomata and increased ψL after a short-lived depression of ψL. The pattern of closure remained unchanged when ψ`L depression was avoided by starting flooding at the end rather than at the start of the photoperiod. Raising external CO2 concentrations by 100 µmol mol−1 also closed stomata rapidly. Five chlorophyll fluorescence parameters [Fq′/Fm′, Fq′/Fv′, Fv′/Fm′, non-photochemical quenching (NPQ) and Fv/Fm] were affected by flooding within 12–36 h and changes were linked to decreased Ci. Closing stomata by applying abscisic acid or increasing external CO2 substantially reproduced the effects of flooding on chlorophyll fluorescence. The presence of well-aerated adventitious roots partially inhibited stomatal closure of flooded plants. Allowing adventitious roots to form on plants flooded for >3 d promoted some stomatal re-opening. This effect of adventitious roots was not reproduced by foliar applications of benzyl adenine and gibberellic acid.

Conclusions

Stomata of flooded plants did not close in response to short-lived decreases in ψL or to increased Ci resulting from impaired PSII photochemistry. Instead, stomatal closure depressed Ci and this in turn largely explained subsequent changes in chlorophyll fluorescence parameters. Stomatal opening was promoted by the presence of well-aerated adventitious roots, implying that loss of function of root signalling contributes to closing of stomata during flooding. The possibility that this involves inhibition of cytokinin or gibberellin export was not well supported.

Keywords: Root to shoot communication; flooding stress; stomatal closure; photosynthesis; chlorophyll fluorescence; gas exchange; adventitious roots; plant hormones; abscisic acid; cytokinins; gibberellic acid

Journal Article.  7770 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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