Photosynthate Distribution in Natural Stands of Salt Water Cordgrass1

Abstract Spartina alterniflora Loisel. is a major grass species of Atlantic coast tidal marshes which contributes heavily to the primary productivity of estuarine ecosystems. As human activity increases in marsh areas, the capability of marsh vegetation to withstand disturbance must be understood and constitute the basis for formulating sound management programs. Toward this end, the seasonal distribution of photoassimilated carbon was studied in S. alterniflora growing under natural conditions. Single culms were exposed to 14 CO 2 at various times during the 1970 and 1971 growing seasons. Plants were harvested 1, 3, and 7 days following exposure to 14 CO 2 . subdivided into leaves, culm, rhizomes, and roots; and each portion assayed for 14 C. Assimilate translocation reached a more or less stable distribution pattern within 24 hours. Throughout much of the growing season, most photosynthate was retained in leaf and culm tissue with less than 10% translocated to roots and rhizomes. Only during early autumn was substantial photosynthate translocated into rhizomes. This and seasonal carbohydrate levels within perennial organs indicate that the stability of S. alterniflora stands may be adversely affected by summer disturbance especially defoliation.