Mechanisms of growth inhibition of sugarcane (saccharum spp) straw on Bidens subalternans L.

SAMPIETRO, D.A.; SGARIGLIA, M.A.; SOBERÓN, J.R.; QUIROGA, E.N.; VATTUONE, M.A.

California - Estados Unidos

Congreso; Botany 2006; 2006

Botanical Society of America - American Bryological and Lichenological Society - American Society of Plant Taxonomists - American Fern Society

PREVIOUS studies indicated that sugarcane straw left on the field after harvest suppress the growth of weeds from the genus Bidens (Asteraceae). Several authors suggested that leachates from sugarcane straw suppress weed growth through the release of allelochemicals. However, the possible role of organic molecules from sugarcane straw in weed suppression is widely unknown. The aim of this work was: 1) to establish which is the role of organic and inorganic constituents of sugarcane straw on growth inhibition of Bidens subalternans L., 2) to determine the influence of soil microorganisms on the biological activity of straw leachates and 3) to determine if modifications of soil properties can be associated with the observed weed growth inhibition. Assays were conducted in pots, in controlled conditions. Straw leachates were incorporated in sterile soil and in unsterile soil with and without addition of activated charcoal. Leachates from straw ashes were also assayed in unsterile soil. Pregerminated seeds of B. subalternans were used. Root and hypocotyl length were determined in 7-day-seedlings. Leachate concentrations higher than 7 g/l significantly inhibited root elongation of B. subalternans . Addition of activated charcoal eliminated the inhibitory effect at low concentrations and ameliorated it at the highest concentrations assayed suggesting that organic molecules were involved. Root length was shorter in biotic than in abiotic soil suggesting that microbial activity increased growth inhibition. Leachates of straw ashes did not significantly inhibit seedling growth. Soil mineral analysis suggests that straw phytotoxicity is related with organic molecules rather than to variations in inorganic nutrients. Our results suggest that the inhibitory activity of sugarcane straw leachates on root growth of B. subalternans is related with their organic constituents. Further studies are needed to identify and characterize the action of the responsible compounds on root growth of B. subalternans .