Nature of the Interference Mechanism of Sugarcane
(Saccharum officinarum L.) Straw |
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Authors: | Diego A Sampietro Marta A Vattuone |
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Institution: | 1. Cátedra de Fitoquímica, Instituto de Estudios Vegetales, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Espa?a 2903, 4000, San Miguel de Tucumán, Argentina
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Abstract: | Sugarcane (Saccharum officinarum L.) straw left in the field after harvest interferes with the growth of winter and summer weeds. In the last years, there
was a progressive move away from burning sugarcane straw to retaining it on the soil surface after harvest to prevent soil
degradation and environmental pollution. Water-soluble phenolics leachated from straw into soil may suppress weed growth.
A study was carried out to investigate (1) the effect of biotic (unautoclaved) soil treated with burned and unburned sugarcane
straw leachates on seedling growth and foliar proline content of beggarticks (Bidens subalternans L.) and wild mustard (Brassica campestris L.), (2) the modification of sugarcane straw phytotoxicity in abiotic (autoclaved) soil and biotic (unautoclaved) soil plus
activated charcoal, and (3) changes of inorganic ions and phenolic contents in biotic soil after treatment with burned and
unburned sugarcane straw leachate. Unburned straw leachate significantly inhibited root elongation of 7-d-old beggarticks
and wild mustard seedlings. Burned straw leachate did not affect seedling growth of the assayed weeds suggesting that organic
straw phytotoxins were involved. Experiments with activated charcoal, however, did not provide clear evidence supporting the
involve of organic molecules in straw phytotoxicity. Unburned straw leachate incorporated in biotic soil was more inhibitory
than in abiotic soil on root growth suggesting that microbial activity is involved in sugarcane straw interference. There
was no evidence of nutrient microbial immobilization. Unburned sugarcane straw leachate increased total phenolic content in
biotic soil more than in abiotic soil or biotic soil plus charcoal. Burned sugarcane straw leachate did not increase phenolic
compounds levels in biotic soil. Linear regression analysis indicated a strong correlation between levels of soil phenolic
contents and root growth inhibition. Soil characteristics evaluated in soil treated with burned and unburned sugarcane straw
leachate suggest that straw phytotoxicity is related with organic molecules, such as phenolic compounds, rather than to variations
in inorganic nutrients. Unburned straw leachate induced proline accumulation in seedling leaves of both beggarticks and wild
mustard. Proline foliar content was higher in seedlings grown in biotic soil than in seedlings grown in biotic soil plus charcoal
suggesting that straw organic constituents induced proline accumulation. Proline foliar content of seedlings grown in biotic
soil treated with burned straw leachate was not significantly different from water control. The present study showed that
sugarcane straw leachate interferes with seedling growth of beggarticks and wild mustard and that water-soluble phenolics
can play a role in the seedling growth inhibition of the assayed weeds. |
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Keywords: | beggarticks phenolic compounds straw phytotoxicity sugarcane wild mustard |
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