Agriculture Reference
In-Depth Information
Figure 4. Degradation of exogenously applied arbutin (Arb) in nonsterile soil from beneath
Polygonella myriophylla . Dashed lines show the disappearance of arbutin, while solid lines show the
appearance and disappearance of hydroquinone (HQ), which was formed by microbial degradation of
its glycoside arbutin. In sterile soil, arbutin was stable over the time period of the experiment. Bars
indicate standard error. If not shown, standard errors are too small to depict visually. (Original figure
appeared in Weidenhamer and Romeo [11]; used with permission of Plenum Publishing Corp.)
active compound(s) in allelopathic interactions may not be in the same chem-
ical form found in the plant [11].
Role of environmental factors
The scrub environment is harsh. Soils are almost 100% sand, and available
nutrients are low. Soil surface temperatures can reach 50 °C on sunny days,
and there can be periodic drought during breaks between summer rains [9, 15].
The low organic matter and clay content of scrub soils likely increases the
activity of any allelochemicals present in the soil, even though some water-sol-
uble compounds would be expected to leach away during the frequent summer
rains. Environmental stress factors such as high temperatures and nutrient lim-
itation are known to increase the toxicity of allelochemicals, and nutrient lim-
itation also increases allelochemical concentrations in some species [16-17].
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