Infodoc : Sciences, Techniques et Culture

Echinochloa polystachya is a perennial C4 grass, archored in the substrate, which forms large monospecific stands in lakes and on fertile river shores of the Amazon region. Individual plants were monitored weekly and date such as lengths and numbers of internodes ans leaves, and presence of inflorescence were recorded. The life cycle of E. polystachya is strongly influenced by the annual fluctuations in water level and can be divided into terrestrial and aquatic phases. The terrestrial phase starts when the water level drops, exposing the sediments (October/November). As this point, new shoots form from the decaying old stems and root in the sediment, growing vigorously. When the young plants are 1-2m tall the water rises and growth rates increase. In cach plant only on leaf is formed[...]

Echinochloa polystachya is a perennial C4 grass, archored in the substrate, which forms large monospecific stands in lakes and on fertile river shores of the Amazon region. Individual plants were monitored weekly and date such as lengths and numbers of internodes ans leaves, and presence of inflorescence were recorded. The life cycle of E. polystachya is strongly influenced by the annual fluctuations in water level and can be divided into terrestrial and aquatic phases. The terrestrial phase starts when the water level drops, exposing the sediments (October/November). As this point, new shoots form from the decaying old stems and root in the sediment, growing vigorously. When the young plants are 1-2m tall the water rises and growth rates increase. In cach plant only on leaf is formed per node and the total number os leaves is 7-9. After submersion the leaves rot quickly and adventitious roots form at the nodes. During the aquatic phase, when the plants are 6-
7 months old, the flowering period starts (March to September). After September growth rates are reduced, when the water level falls and the roots along the stem become dry. Simultaneously the base of the plant rots due to anoxic conditions in the water. In a complete life cycle (from establishment to decline), one individual plant may grow 15m. Dues to its vigorous growing pattern, high density and productivity, E. polystachya is a key species in the varzea floodplain. Besides contributing to the local ecosystem for the nutrient cycle and being consumed by manatees, cattle, etc, the plant plays an important role in other aquatic environments when it is moved by water currents or wind and through the river system.