High phenotypic plasticity of Suaeda maritima observed under hypoxic conditions in relation to its physiological basis.
OBJECTIVE
Phenotypic plasticity, the potential of specific traits of a genotype to respond to different environmental conditions, is an important adaptive mechanism for minimizing potentially adverse effects of environmental fluctuations in space and time. Suaeda maritima shows morphologically different forms on high and low areas of the same salt marsh. Our aims were to examine whether these phenotypic differences occurred as a result of plastic responses to the environment. Soil redox state, indicative of oxygen supply, was examined as a factor causing the observed morphological and physiological differences.


METHODS
Reciprocal transplantation of seedlings was carried out between high and low marsh sites on a salt marsh and in simulated tidal-flow tanks in a glasshouse. Plants from the same seed source were grown in aerated or hypoxic solution, and roots were assayed for lactate dehydrogenase (LDH) and alcohol dehydrogenase, and changes in their proteome.


RESULTS
Transplanted (away) seedlings and those that remained in their home position developed the morphology characteristic of the home or away site. Shoot Na(+), Cl(-) and K(+) concentrations were significantly different in plants in the high and low marsh sites, but with no significant difference between home and away plants at each site. High LDH activity in roots of plants grown in aeration and in hypoxia indicated pre-adaptation to fluctuating root aeration and could be a factor in the phenotypic plasticity and growth of S. maritima over the full tidal range of the salt marsh environment. Twenty-six proteins were upregulated under hypoxic conditions.


CONCLUSIONS
Plasticity of morphological traits for growth form at extremes of the soil oxygenation spectrum of the tidal salt marsh did not correlate with the lack of physiological plasticity in the constitutively high LDH found in the roots.
Department of Biology and Environmental Science, School of Life Sciences, University of Sussex, Falmer, Brighton, UK. aandrwetson@btinternet.com
Anne M
AM
Wetson
Christian
C
Zörb
Elizabeth A
EA
John
Timothy J
TJ
Flowers
D000222:Adaptation, Physiological / Q000502:physiology*; D018533:Biomass; D015687:Cell Hypoxia / Q000502:physiology; D019663:Chenopodiaceae / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D004777:Environment; D005838:Genotype; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology; D018520:Plant Shoots / Q000254:growth & development / Q000502:physiology; D040901:Proteomics; D055051:Salt-Tolerant Plants; D036226:Seedlings / Q000254:growth & development / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology*; D012987:Soil; D053833:Wetlands
D010940:Plant Proteins; D012987:Soil; D012965:Sodium Chloride; D007770:L-Lactate Dehydrogenase; D010100:Oxygen