Bulletin of the National Institute of Ecology 15: 153-160, 2005 Gupta et al. (Editors): Ecology and Environmental Management: Issues and Research Needs © NATIONAL INSTITUTE OF ECOLOGY, NEW DELHI & JAIPUR Growth and Biomass Allocation in Scirpus littoralis Schrad. Under Different Water Depths RITA CHAUHAN School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067 Email: rita_env@yahoo.com ABSTRACT The young plants of S. littoralis of uniform size (culm length 30 cm) were subjected to four different water depths of 0 cm (control), 5 cm, 15 cm and 30 cm. Growth parameters such as culm length, culm diameter, number of new tillers, size of inflorescence and biomass accumulation were recorded every two weeks for twelve weeks. At last (sixth harvest), the total number of tillers produced in 0 cm water depth was 5, which increased to 8 at 15 cm and then declined to 4 at 30 cm water depth. The secondary tillers were longer than primary culm. The aboveground biomass at fifth harvest increased from 2.33 g at 0cm and 2.8g at 5cm to 5.8g at 15 cm and then declined to 4.0g at 30cm water depth. Similarly the belowground biomass increased from 0.38g at 0cm water depth to 0.68g at 5cm to 1.14g at 15cm and the decreased to 0 .83g at 30cm water depth. The aboveground to belowground biomass initially decreased but after eight weeks growth, the plant accumulated more biomass in belowground organs, which is typical character of perennial species. The number and size of spikelets and the inflorescence biomass also increased with water level from 0 to 15 cm and declined at 30cm. The statistical analysis (ANOVA with n=4, F crit =0.05) showed that water depth treatment had affected the growth and reproduction of S. littoralis significantly. Key Words: Water Depth, Emergent Macrophyte, Growth, Biomass Allocation, Scirpus littoralis INTRODUCTION Water regime, which is defined as the integration of continuously changing depth over time, is a major determinant of plant community development and patterns of plant zonation in wetlands (Rea and Ganf 1994). Water depth is the prime physical factor that varies along elevational gradient in wetland habitat. The depth range a species occupies is determined by its tolerance to gradient of factors that vary with depth (such as soil moisture, particle size, duration and depth of submergence, wave action) and competition with other species with overlapping tolerances (Keddy and Constabel 1986, Sorrell et al. 2002). Increased water level depletes soil oxygen, which affect plant metabolism and growth through mechanisms such as reduced photosynthesis, altered nutrient uptake and hormonal imbalance (Kozlowski 1984). The emergent plants develop phenotypic plastic response such as changes in the number and height of stems and rhizome size (Vretare et al. 2001).