The allelopathic effects of plants

Topics: Weed, Allelopathy, Botany Pages: 17 (542 words) Published: June 26, 2014
THE ALLELOPHATIC EFFECT
OF PLANTS
Raluca Elena Hedes

STRUCTURE:
PART 1: Clarifying THEORETICAL CONCEPTS
and TERMINOLOGY
¨  PART 2: Aspects of PRACTICAL APLICABILITY
¨  PART 3: SOURCES
¨  PART 4: Q&A
¨ 

The term allelopathy…
¨ 

¨ 
• 
• 

1937 – introduced by Prof. Hans Molisch

Derived from the Greek words:
Allelon = of each other
Pathos = to suffer

Definition
¨ 

1996 - The International Allelopathy Society:

“Any process involving secondary metabolites
produced by plants, micro-organisms, viruses, and
fungi that influence the growth and development of
agricultural and biological systems (excluding
animals), including positive and negative
effects” (Torres et al. 1996 in Kruse et al. 2000)

Definition (simplified J )

¨ 

Biochemical inhibition of one plant by
another through the release of
allelochemicals

Source: Muller, 1969

Allelochemicals
Chemicals released from plants and imposing
allelopathic influences
¨  Allelochemicals can be found in several parts of the plant:
•  roots
•  rhizomes
•  leaves
•  stems
•  pollen
•  seeds
•  flowers
¨ 

Source: Kruse, M., et al., (2000). Ecological Effects of Allelopathic Plants – a Review

Allelopathy and Competition
Competition – the process in which the reaction of a
plant reduces the level of some necessary factor to
the detriment of another plant sharing the same
habitat
¨  E.g. radiant energy, oxygen, CO2, mineral nutrients, water
¨  Allelopathy does NOT involve the depletion of a
necessary factor and depends upon the addition of
a deleterious factor (a chemical compound)
¨ 

Source: Muller, 1969

Dependence
The phenomenon of favorable response to any
reaction upon the habitat by another organism
¨  When allelopathy favors the existence of some
species – dependence based upon chemical
reactions
¨  When competition favors the existence of some
species – dependence based upon physical
reactions
¨ 

Source: Muller, 1969

Dominance
¨ 

¨ 

Dominant species are the most abundant and
exert the most influence or control on the
habitat and other species
Distinction: Allelopathic dominance vs.
Competitive dominance

Source: Muller, 1969

Succession
¨ 
¨ 
¨ 

¨ 

¨ 
¨ 

“Auto-intoxication”
Disappearance of the pioneer species
New plant species take hold of the “disturbed habitat”
and modify it
These changes allow better suited plants to succeed the
old species into the modified habitat…
…And so on…
Climax community – a stable environment dominated by
a small number of prominent species
Source: Muller, 1969

ALLELOPATHY ROCKS!

HOW COME?

Prospects for application of
allelopathy to farming
Alternative strategies for weed management
=> The reliance on traditional herbicides in crop
production can be reduced
¨  Today, the allelopathic activity of some cropsis
to some extent used in weed management
¨ 

Source: Kruse, M., et al., (2000). Ecological Effects of Allelopathic Plants – a Review

Allelopathic crops
Allolopathic crops used in weed suppression:
¨  Rye (Secale cereale)
¨  Wheat (Triticum aestivum)
¨  Barley (Hordeum vulgare)
¨  Oats (Avena spp)
¨  Rice (Oryza sativa)

Source: Kruse, M., et al., (2000). Ecological Effects of Allelopathic Plants – a Review

Prospects for application of
allelopathy to farming
¨ 

Natural herbicides - search and development
of new herbicides through the isolation,
identification and synthesis of active
compounds from allelopathic plants

Source: Kruse, M., et al., (2000). Ecological Effects of Allelopathic Plants – a Review

Reduced pollution?
¨ 

Due to their origin from natural sources, some
authors suggest that the allelopathic compounds will
be biodegradable and less polluting than
traditional herbicides

Source: Kruse, M., et al., (2000). Ecological Effects of Allelopathic Plants – a Review

Sources
¨ 

¨ 

¨ 

Muller, C....
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