5.2
Exploring Hormesis to Suppress Weeds
Hormesis of allelochemicals can play an important role for sustainable weed management. The dose-response effect of allelochemicals (inhibition at higher concentrations and growth enhancement at low concentrations) can be used in crop
production to enhance crop growth with inhibition in weeds [90]. For example,
application of hormetic dose to crop plants can produce herbicidal effect to weeds at
their growth sensitive stage (early seedling stage). Optimization of dose, source, and
application time of allelochemicals to produce hormesis in crop plants and inhibition
in weeds might be an effective way to control weeds on a sustainable basis. Abbas
et al. [90] reviewed that the various types of allelochemicals released from different
crop and weed species produced hormesis (growth enhancement) in range of crop
species at low doses, the same hormetic doses produced herbicidal effect when
applied to weeds at their early seedling stage. Thus hormesis of allelochemicals
will increase weed suppressive ability of crop by enhancing crop growth and by
inhibiting weed growth due to their herbicidal effect. Therefore, future research in
this regard will open new horizons for sustainable weed management.
5.3
Allelopathy of Unexplored Fields
The allelopathy of unexplored field can help to provide novel allelochemicals with
more herbicidal potential. For example, allelopathic effect of aquatic weeds was
more suppressive against various types of terrestrial weed species (Abbas et al.
2017). The susceptibility of crop weeds against allelochemicals from different
ecosystem (aquatic in this case) was due to low adaptability of terrestrial weeds.
Thus, more studies about determination and identification of allelochemicals of
aquatic weeds can help to evaluate strong natural herbicide candidates. Furthermore,
secondary metabolites released from lichen showed phytotoxicity to lichen photosynthetic process both when used alone and in the form of naturally occurring
mixtures [87]. Similarity, allelochemicals released from fungi showed herbicidal
effect against some weed species, e.g., P. hysterophorus L. [88]. Further studies in
these ignored fields might identify novel strong herbicidal candidates.
5.4
Understanding About Mode of Action of Allelochemicals
Studies about how allelochemicals work have prime importance in allelopathic
studies and require understanding at the molecular level, e.g., the structure of
binding sites of protein or DNA. The knowledge about mode of action of natural
phytotoxins can help to fasten the further industrial level consideration to produce
natural herbicides. Recently few research attempts have been made to understand the
mode of action of allelochemicals, e.g., Ren et al. [89] revealed that β-cembrenediol
an important allelochemical inhibits the receptor plants through oxidative damage
due to increased production of reactive oxygen species.
514
N. Farooq et al.
Exploring Hormesis to Suppress Weeds
Hormesis of allelochemicals can play an important role for sustainable weed management. The dose-response effect of allelochemicals (inhibition at higher concentrations and growth enhancement at low concentrations) can be used in crop
production to enhance crop growth with inhibition in weeds [90]. For example,
application of hormetic dose to crop plants can produce herbicidal effect to weeds at
their growth sensitive stage (early seedling stage). Optimization of dose, source, and
application time of allelochemicals to produce hormesis in crop plants and inhibition
in weeds might be an effective way to control weeds on a sustainable basis. Abbas
et al. [90] reviewed that the various types of allelochemicals released from different
crop and weed species produced hormesis (growth enhancement) in range of crop
species at low doses, the same hormetic doses produced herbicidal effect when
applied to weeds at their early seedling stage. Thus hormesis of allelochemicals
will increase weed suppressive ability of crop by enhancing crop growth and by
inhibiting weed growth due to their herbicidal effect. Therefore, future research in
this regard will open new horizons for sustainable weed management.
5.3
Allelopathy of Unexplored Fields
The allelopathy of unexplored field can help to provide novel allelochemicals with
more herbicidal potential. For example, allelopathic effect of aquatic weeds was
more suppressive against various types of terrestrial weed species (Abbas et al.
2017). The susceptibility of crop weeds against allelochemicals from different
ecosystem (aquatic in this case) was due to low adaptability of terrestrial weeds.
Thus, more studies about determination and identification of allelochemicals of
aquatic weeds can help to evaluate strong natural herbicide candidates. Furthermore,
secondary metabolites released from lichen showed phytotoxicity to lichen photosynthetic process both when used alone and in the form of naturally occurring
mixtures [87]. Similarity, allelochemicals released from fungi showed herbicidal
effect against some weed species, e.g., P. hysterophorus L. [88]. Further studies in
these ignored fields might identify novel strong herbicidal candidates.
5.4
Understanding About Mode of Action of Allelochemicals
Studies about how allelochemicals work have prime importance in allelopathic
studies and require understanding at the molecular level, e.g., the structure of
binding sites of protein or DNA. The knowledge about mode of action of natural
phytotoxins can help to fasten the further industrial level consideration to produce
natural herbicides. Recently few research attempts have been made to understand the
mode of action of allelochemicals, e.g., Ren et al. [89] revealed that β-cembrenediol
an important allelochemical inhibits the receptor plants through oxidative damage
due to increased production of reactive oxygen species.
514
N. Farooq et al.