3. Decomposition of residues – It is challenging to determine if these toxic entities
are encompassed in residues and released upon decomposition or microorganisms
transform the simple residues into these toxic elements as an outcome of the
existence of microbial enzymes (Mushtaq and Siddiqui 2018; Kohli et al. 2001).
4. Root exudation – Root perspiration of allelochemicals from plant roots bequeaths
one of the major direct allelochemicals into the rhizosphere zone in the soil,
regardless of whether these compounds are effectively exuded, leaked, or arise
from dead cells (Bertin et al. 2003).
5. Allelochemicals released from pollen – Pollen allelopathy occurs when pollen
grains are transmitted either inter- or intraspecific transfer. The pollen allelopathy
occured either pollen transmitted either inter oe intraspecific transfer due to pre
and post zygotic barriers (Murphy 2001).
There are wide variations in the natural and agroecosystems as the mode of
release pattern of allelochemical discharge into the atmosphere is contingent on
the physicochemical traits and the plant organ involved in allelopathic interaction.
2.3 Factors Affecting the Production and Release
of Allelochemicals
The biosynthesis and release of allelochemicals are controlled by various factors,
such as genetic, environmental, ecological, and physiological factors. Nevertheless,
allelochemical type and concentration released into the environment determined the
communal effects of the plant itself and environmental factors.
2.3.1 Genetic Factors
The plant features include the species, variety, plant and its development stages,
the organs and tissues, which are interrelated to allelochemical production and
release (Iannucci et al. 2013). The production of allelochemicals through secondary
metabolism in plants is dependent on the genetic element responsible. Numerous
studies have been conducted to know the molecular and genetic basis for abiotic
stress or herbivores and pathogen infection signaling in plants, but less effort has
been devoted to allelopathy responses. Research has validated that genetic variation
of the allelopathic traits is in a wide range in within crop species (Dilday et al. 1991;
Olofsdotter et al. 1999; Jensen et al. 2001). Allelopathic properties differ between
varieties or genotypes (Li and Shen 2006): as an example, a rice (Oryza sativa L.)
breeding program that undertaken the evolution of cultivars with increased level
allelochemical synthesis has advanced from the elucidation of the enzymes and
genes involved in momilactone B synthesis (Toyomasu et al. 2008). Momilactone
B is a diterpene compound that suppresses weed at a maximum degree. By using the
reverse genetics technique, it became possible to identify the genes encoding
5 Allelochemicals as Natural Herbicides for Sustainable Agriculture to Promote. . .
101
are encompassed in residues and released upon decomposition or microorganisms
transform the simple residues into these toxic elements as an outcome of the
existence of microbial enzymes (Mushtaq and Siddiqui 2018; Kohli et al. 2001).
4. Root exudation – Root perspiration of allelochemicals from plant roots bequeaths
one of the major direct allelochemicals into the rhizosphere zone in the soil,
regardless of whether these compounds are effectively exuded, leaked, or arise
from dead cells (Bertin et al. 2003).
5. Allelochemicals released from pollen – Pollen allelopathy occurs when pollen
grains are transmitted either inter- or intraspecific transfer. The pollen allelopathy
occured either pollen transmitted either inter oe intraspecific transfer due to pre
and post zygotic barriers (Murphy 2001).
There are wide variations in the natural and agroecosystems as the mode of
release pattern of allelochemical discharge into the atmosphere is contingent on
the physicochemical traits and the plant organ involved in allelopathic interaction.
2.3 Factors Affecting the Production and Release
of Allelochemicals
The biosynthesis and release of allelochemicals are controlled by various factors,
such as genetic, environmental, ecological, and physiological factors. Nevertheless,
allelochemical type and concentration released into the environment determined the
communal effects of the plant itself and environmental factors.
2.3.1 Genetic Factors
The plant features include the species, variety, plant and its development stages,
the organs and tissues, which are interrelated to allelochemical production and
release (Iannucci et al. 2013). The production of allelochemicals through secondary
metabolism in plants is dependent on the genetic element responsible. Numerous
studies have been conducted to know the molecular and genetic basis for abiotic
stress or herbivores and pathogen infection signaling in plants, but less effort has
been devoted to allelopathy responses. Research has validated that genetic variation
of the allelopathic traits is in a wide range in within crop species (Dilday et al. 1991;
Olofsdotter et al. 1999; Jensen et al. 2001). Allelopathic properties differ between
varieties or genotypes (Li and Shen 2006): as an example, a rice (Oryza sativa L.)
breeding program that undertaken the evolution of cultivars with increased level
allelochemical synthesis has advanced from the elucidation of the enzymes and
genes involved in momilactone B synthesis (Toyomasu et al. 2008). Momilactone
B is a diterpene compound that suppresses weed at a maximum degree. By using the
reverse genetics technique, it became possible to identify the genes encoding
5 Allelochemicals as Natural Herbicides for Sustainable Agriculture to Promote. . .
101