[show abstract][hide abstract] ABSTRACT: 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.
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.
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.
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.
Annals of Botany 02/2012; 109(5):1027-36. · 3.45 Impact Factor
[show abstract][hide abstract] ABSTRACT: Habitats occupied by many halophytes are not only saline, but are also prone to flooding and yet surprisingly few studies have evaluated submergence tolerance in halophytes. Sediment, floodwater, and intra-plant O2 dynamics were evaluated during tidal submergence for the leaf-succulent halophyte Suaeda maritima (L) Dum. For S. maritima growing in soil just above the mud flat in a UK salt marsh, the soil was only moderately hypoxic just prior to tidal inundation, presumably owing to drainage and O2 entry facilitated by frequent, large cracks. O2 declined to very low levels following high tide. By contrast, mud flat sediment remained waterlogged, lacked cracks, and was anoxic. Plant O2 dynamics were investigated using field-collected plants in sediment blocks transported to a controlled-submergence system in a glasshouse. Submergence during night-time resulted in anoxia within leaves, whereas during day-time O2 was produced by underwater photosynthesis. The thin lateral roots of S. maritima presumably access some O2 from hypoxic sediments, but could also experience transient episodes of severe hypoxia/anoxia, especially as any internal O2 movement from shoots would be small owing to the low gas-filled porosity in roots. Fermentative metabolism to lactate, producing some ATP in the absence of O2, might contribute to tolerance of transient O2 deficits. Lactate was high in root tissues, whereas ethanol production (tissue and incubation medium contents) was low, both in comparison with values reported for other species. Our findings demonstrate the importance of tolerance to transient waterlogging and submergence for the halophyte S. maritima growing in a tidal salt marsh.
Environmental and Experimental Botany 01/2012; · 2.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: Salinity is an increasing problem for agricultural production worldwide. The result of low-affinity Na(+) uptake is toxic to the cytoplasm of most crop plants. Nevertheless, the pathways for this low-affinity Na(+) uptake are still uncertain. In this work we used ²²Na(+) isotope tracing technology to investigate factors associated with determination of root ²²Na(+) influx in the salt accumulation halophyte Suaeda maritima. We found that a 2 min of exposure to the ²²Na(+) labeled uptake solution was optimal for determining ²²Na(+) influx into excised roots of S. maritima and that 7 min of blotting is suitable in ²²Na(+) influx experiments. ²²Na(+) influx did not increase linearly with the increasing external Na(+) concentration, in the range tested, of 2 to 300 mM NaCl. But root ²²Na(+) influx and root Na(+) concentration were well correlated. ²²Na(+) influx into excised roots of S. maritima was not, however, well correlated with the plant size. All the above results indicated further that this ²²Na(+) isotope influx procedure is a good method for quantify Na(+) uptake rate by the roots of the salt accumulation halophyte.
Biological trace element research 03/2010; 139(1):108-17. · 1.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: Seeds of annual halophytes such as Suaeda maritima experience fluctuating salinity, hydration, hypoxia and temperature during dormancy. Germination then occurs in one flush of 2-3 weeks after about 5 months of winter dormancy during which time the seeds can remain in saline, often waterlogged soil. The aim of this study was to investigate the effect of simulated natural conditions during dormancy on germination and to compare this with germination following the usual conditions of storing seeds dry. The effects of hydration, salinity, hypoxia and temperature regimes imposed during dormancy on germination were investigated. Also looked at were the effects of seed size on germination and the interaction between salinity during dormancy and salinity at the time of germination.
Various pre-treatments were imposed on samples of seeds that had been stored dry or wet for different periods of time during the 5 months of natural dormancy. Subsequent germination tests were carried out in conditions that simulated those found in the spring when germination occurs naturally. Various salinities were imposed at germination for a test of interaction between storage salinity and salinity at germination.
A temperature of about 15 degrees C was needed for germination and large seeds germinated earlier and better than small seeds. Cold seawater pre-treatment was necessary for good germination; the longer the saline pre-treatment during the natural dormancy period the better the germination. There appeared to be no effect of any specific ion of the seawater pre-treatment on germination and severe hypoxia did not prevent good germination. A short period of freezing stimulated early germination in dry-stored seed. Storage in cold saline or equivalent osmotic medium appeared to inhibit germination during the natural dormancy period and predispose the seed to germinate when the temperature rose and the salinity fell. Seeds that were stored in cold wet conditions germinated better in saline conditions than those stored dry.
The conditions under which seeds of S. maritima are stored affect their subsequent germination. Under natural conditions seeds remain dormant in highly saline, anoxic mud and then germinate when the temperature rises above about 15 degrees C and the salinity is reduced.
Annals of Botany 07/2008; 101(9):1319-27. · 3.45 Impact Factor