Ecological Adaptations of Salt Marsh Grass, Distichlis spicata (Gramineae), and Environmental Factors Affecting Its Growth and Distribution

Abstract

Salt grass is an important pioneer plant in early stages of succession. The sharp‐pointed rhizomes with numerous epidermal silica cells, and the aerenchymatous network of the rhizome, leaf sheath, and roots facilitate development of the plant in heavy clays, shales, and inundated soils. In salt marshes of southern Utah, salt grass contributes to a hummock‐building process that favors localized removal of salts by capillary action and evaporation. This process provides a narrow strip of soil that is favorable for the rooting of extended rhizomes. In laboratory experiments, maximum growth for Distichlis spicata, a perennial salt marsh grass, was obtained at 15,000 ppm soluble salts in nutrient solution cultures. Comparable concentrations of salts occurred in soils of the habitat from which plants were taken. Nearly equal concentrations of sodium and potassium were found in the plant tissue where the growth of the plants was optimal; such a ratio was maintained in the plants during most of the growing season. In the field the greatest amount of growth of salt grass takes place when temperatures are cool and soil moisture is quite high during the early spring. During mid‐summer as air temperatures rise, crude protein in the plant decreases. During periods of high salt and water stress, morphological and anatomical adaptations of the stomata, salt glands, and trichomes of salt grass are important for survival. Stomata on exposed ridges of vascular bundles, where desiccation is greatest, usually are covered by four epidermal cells. In contrast, stomata found in the grooves between vascular bundles tend to be uncovered. The salt gland is composed of a large basal cell and a cap cell and actively excretes (in a diurnal rhythm) excess sodium, potassium, and chloride ions. A mechanism for salt excretion from this gland is postulated. The silica‐containing trichomes on the leaves may play a role in cooling the leaf under conditions of high solar radiation and also serve to protect the plant against attack by herbivores.

Nipa (Distichlis palmeri): A perennial grain crop for saltwater irrigation

“…Adaxial leaf surfaces of D. palmeri have alternating long and short epidermal cells arranged in a ridge and furrow system, exposed-type stomata in the furrow portion of the leaf with knob-like protrusions from each guard cell, and bicellular microhairs (salt glands) in the furrows and on the sides of ridges, also typical of D. spicata. We did not observe silica saddle cells or trichomes in D. palmeri, but these can be absent from greenhouse-grown D. spicata plants as well (Hansen et al, 1976). Root tips from four separate plants grown from seeds collected for this study had somatic chromosome counts of 40 during mitosis, the same as the initial report by Gould (1966) and for D. spicata.…”

“…Rhizome sections of D. palmeri (Fig. 5) have scattered vascular bundles, a suberized endodermis, and a layer of aerenchyma tissue between the epidermis and stele, typical of D. spicata (Hansen et al, 1976). Adaxial leaf surfaces of D. palmeri have alternating long and short epidermal cells arranged in a ridge and furrow system, exposed-type stomata in the furrow portion of the leaf with knob-like protrusions from each guard cell, and bicellular microhairs (salt glands) in the furrows and on the sides of ridges, also typical of D. spicata.…”

“…High RGR values were maintained over two harvests, indicating that D. palmeri could be subjected to multiple cuttings if grown as a forage crop, since it readily produced new shoots from rhizomes even when cut back to the soil line. Like D. spicata (Hansen et al, 1976), D. palmeri developed aerenchyma tissues under flooded conditions, allowing it to keep the roots aerated even in highly anaerobic soils. Salinity had a negative effect on shoot (stem) densities in the greenhouse study, which ranged from 900e4000 shoots per m 2 over the salinity range of 0e30 g L À1 , with low-end values typical of field values in the Río Colorado delta.…”

Salinity Effects on Germination and Plant Growth of Prairie Cordgrass and Switchgrass

“…Compared with Cave-in-Rock, Red River handled high salt stress by excretion of salt through salt glands onto leaf surfaces [18,50], which prevented the accumulation of Na + in shoot biomass. Bradley and Morris [9] reported similarly that S. alterniflora excreted more than 90% of theoretical maximum Na + that entered into the shoots through salt glands avoiding toxic buildup of Na + in the apoplastic tissue of the leaves and keeping the leaves alive during extended salt exposures [16]. Although the selectivity of K + over Na + in root and shoot biomass of both species was high at high salinity levels, uptake of essential cations such as Mg 2+ and Ca 2+ by roots decreased due to ion interaction, precipitation, and increases in ionic strength that reduce the activity of Ca 2+ and Mg 2+ [3].…”

Southern California Salt Marsh Dominance Relates to Plant Traits and Plasticity

“…In wetter habitats, it becomes decumbent, and in intermittently tidal marshes, it becomes woody and grows up to a meter tall (Zedler et al 1980). Factors that increase canopy height include relief from drought (Chaves et al 2003), soil nutrient additions (Boyer and Zedler 1998), CO 2 additions (Pritchard et al 1999), relief from waterlogging (this study), and growth at optimal salinity (Hansen et al 1976;Ke-fu et al 1986;Parida et al 2004).…”