The effect of long-term submergence on functional properties of Eleocharis cellulosa Torr.

Eleocharis cellulosa Torr., a macrophyte dominating marshes of northern Belize, often experiences great water level fluctuations varying from dry conditions to prolonged submergence. We investigated morphological and ecophysiological responses (shoot length, biomass, CO2 exchange, chlorophyll content and regeneration) to partial and complete submergence followed by emergence in two field experiments. Submergence greatly enhanced shoot elongation, but it also resulted in a low number of viable shoots, lower biomass and consequently in lower plant fitness. The decline in live shoot length started after 3 months of submergence. The shoots produced by submerged plants were thin and would break easily if the water level decreased fast. Photosynthetic activity, as well as respiration rate, was highly reduced in shoots just emerged from complete submergence. The ability of E. cellulosa to retain some level of photosynthesis after emergence is undoubtedly a useful trait in coping with seasonal floods. Submerged plants produced chlorophyll, especially Ch a, for at least a period of 3 months. Shoot regeneration was significantly slower in the case of plants submerged for a longer time, probably due to depleted energy reserves, but there were no significant differences in the total shoot length among treatments after 2 months following the emergence. E. cellulosa demonstrated high tolerance to long-term (more than 4 months) complete submergence and resulting anoxic conditions and showed rather fast recovery after emergence. This can be viewed as an advantageous trait in habitats of rapid and prolonged increases of water level and also after water recedes, when vegetation starts to colonize newly opened space.