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1 January 2009 Characterization of internal airflow within tissues of mangrove species from Australia: leaf pressurization processes
Lance S. Evans, Zachary M. Testo, Jonathan A. Cerutti
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Mangroves are a diverse group of plants that inhabit tidal zones in the tropics and sub-tropics. Some mangrove species occupy the lower tidal zone in which the substrate is anoxic for long time periods while some mangroves inhabit the upper tidal zone in which the substrate should be less anoxic. The purpose of this study was to determine if twenty-four species of mangroves have a mechanism of internal airflow to provide air to roots within anoxic substrates. Results show that 11 species pressurize air in leaves and move this air internally in aerenchyma tissues in stems and eventually to roots while 13 mangrove species do not move air internally from leaves to roots. Quantitative data showed that the internal airflow from leaves to roots for these 11 mangrove species was correlated with 1) number of cork warts on leaves, 2) volume of aerenchyma tissues within leaves, and 3) the volume of aerenchyma tissues in stems relative to the number of leaves on stems. Higher values of these three parameters were negatively related (y  =  64.8 x−0.36 with an r2 of 0.93) with the minimum air pressure required to release air pressure from foliage when air pressure was applied to cut stems of whole plants. Each of the three characteristics above is required for air conductance from leaves to roots. Indeed, relative internal airflow from roots to stems in these 11 mangrove species can be accounted for by these three factors alone. Some mangrove species only have aerenchyma in their roots and can move air internally from pneumatophores to other roots within the anoxic substrate. Some mangrove species that occupy the upper tidal zone do not have aerenchyma tissues to move air internally. To our knowledge, this is the first report that 1) provides extensive air pressure testing of tissues for many mangrove species, 2) extensively quantifies morphological and anatomical data to account for internal air movement from leaves to roots, and 3) quantifies internal air movement and provides anatomical data to help explain the predominant location that many mangrove species occupy in the tidal and estuary zones of Australia.

Lance S. Evans, Zachary M. Testo, and Jonathan A. Cerutti "Characterization of internal airflow within tissues of mangrove species from Australia: leaf pressurization processes," The Journal of the Torrey Botanical Society 136(1), 70-83, (1 January 2009).
Received: 11 July 2008; Published: 1 January 2009

cork warts
internal airflow
quantitative anatomy of tissues involved with internal airflow from leaves to roots
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