Seeds of Triglochin striata, a small perennial salt marsh plant, were grown under controlled laboratory conditions under a range of salinity treatments. After an initial growth period and acclimation to the treatment media, plants were harvested at two weekly intervals for ten weeks. At each harvest the shoots and roots were separated and wet and dry weights and ion concentrations determined. Serial segments of shoot and root were also taken from each harvest and oxygen consumption measured with a Clarke electrode. Relative growth rates of Triglochin striata as a function of time and treatment were calculated. Growth and maintenance respiration of roots and shoots were also derived as a function of salinity treatment. The results show an apparent depression of growth of the plants below and above 25% sea-water treatment media. This result is explained in terms of the other parameters that were determined.