Clonal integration in Spartina patens across a nitrogen and salinity gradient

Abstract

We investigated physiological integration among ramets of Spartina patens when clones spanned a salinity gradient. Clones of S. patens were grown in paired pots with the ramets of the parent pot connected to the ramets of the daughter pot via a common rhizome. Half of these clones had the rhizome connection between parent and daughter pots severed immediately prior to treatment application. The parent pots were kept at low salinity (34.2 mM NaCl) and given two levels of labeled 15NH4Cl (0.036 or 0.714 mM NH4Cl). Daughter ramet pots were kept at the low N level (unlabeled 0.036 mM NH4Cl) and exposed to an increase in salinity to 513 mM NaCl. After 7 days, all daughter ramets had significantly elevated leaf Na levels. Daughter ramets connected to parents were able to maintain significantly greater leaf elongation rates than severed daughter ramets. Labeled 15N was translocated from parents to connected daughter ramets and high-N parents translocated more N to the belowground tissue of daughter ramets than low-N parents. Leaf proline, a nitrogen-containing osmoticum that accumulates only after a threshold of salinity stress is exceeded, was significantly increased only in severed daughter ramets, indicating that salinity stress was reduced in connected daughter ramets, possibly via parental water translocation. Key words: clone, physiological integration, proline, ramet, salt marsh, salt stress.

Growth form and population density ofSpartina maritima (Curtis) Fernald in northwest Spain

“…This hypothesis is consistent with the fact that species of the genus Spartina reproduce largely by clonal expansion, with seed set typically being extremely low (Castellanos 1992, Daehler and Strong 1994, Shumway 1995. Furthermore, ramets typically remain connected to the mother plant by rhizomes (Dai and Weigert 1996), so that members of a clone are able to 'help' other members that are suffering localized environmental stress (i.e., 'physiological integration'; Hester et al 1994, Shumway 1995. In view of these factors (genetic homogeneity and physiological integration), and given that our edaphic data do not explain the observed differences in height, S. maritima can be expected to occur in phenotypically homogeneous stands.…”

Assessment of carbon allocation and biomass production in a natural stand of the salt marsh plant Spartina anglica using 13C

“…Translocation of nitrogen-containing compounds was recently reported in Spartina patens (Hester et al 1994). Obviously, source-sink relations exist between connected ramets of Spartina spp., as has been found in other clonal plant species (see e .…”

Cordgrass Biomass in Salt Marshes

“…S. argentinensis, S. densiflora, S. bakeri, S. patens and S. versicolor forms dense tussocks that show a high occupation of available space inside tussocks by live shoots in expanding populations and by live and dead shoots in mature populations (Figueroa & Castellanos, 1988;Nieva et al, 2001b). These dense tussocks seem to show a high degree of physiological integration between ramets (Hester et al, 1994 for S. patens) reflected in very low mortality rates of young shoots (Pitelka & Ashmun, 1985;Maillette, 1992). Thus, interior areas of "phalanx" tussocks are not easily colonized by other species unless they develop central die-back areas (known as "monk's tonsure").…”