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weed seed dispersal mechanisms

entomochoric: seed dispersed by the agency of insects

hydrochoric
: seed dispersed by the agency of water

myrmecochorous
: seed dispersed by the agency of ants

Animal storage of seed: distance, concentration, location

Ants play important role, especially in storage concentrations

anemochorous seed: dispersed by the agency of wind

the expanding range and increasing population size of of an invading weed species into a new area

Wind-blown seed, or seeds on the soil surface moved by water:
-accumulate near obstacles (fences, furrows, etc.), or fall in soil crevices, dried soil cracks
-Composite family weeds with pappus (or other similar attached seed structure) on the seed are held at a constant distance in the crack (soil) by the pappus and do not enter the crack.

Ants play important role, especially in storage concentrations


Gravity dispersal: most of our common, unspecialized weed seeds don’t move very far from mother plant without animals, humans
-preventative weed control is very important
-invasion from the outside overemphasized

Specialized seed structures affect whether, and how, animals spread seed:
-burrs: cocklebur, sandbur seed
-appendages: beggarticks seed

Selection for time of seed release: adaptation for quick or slow release from parent plant?
-quick release: oversaturate predator demands of feeding and leave enough after that for new colonizers
-slow release: maximize chance some seeds land on ground during favorable time for quick germination or escape from predators

Differences in time:
-seed ripens on parent plant
-seed retained on parent before its dispersed (seed shattering)
-example: weeds with long flowering period and corresponding long period of ripening and release: seed shatters immediately after ripening on parent
-example: weeds flowering and seed production in narrower time period, often require harvesting activity to release seed: evolved with crop, maximize chance of dispersal with crop

This paper reviews the current knowledge on weed seed movement in an agricultural environment. Seed movement is analyzed both from an agronomic and ecological perspective, focusing predominantly on horizontal seed movement. Abiotic (anemochory and hydrochory), as well as biotic (autochory, myrmecochory, epizoochory, and endozoochory) weed seed dispersal typologies are examined, highlighting the mechanisms involved, the specializations displayed by weed species that have evolved by exploiting a particular dispersal mechanism, and their adaptive interaction with the surrounding ecosystem. Emphasis is also placed on the crucial role of human activity (anthropochory), which can affect natural (biotic and abiotic) weed seed dispersal at several stages, partly via the worldwide commercial seed trade but, above all, by crop management operations, thereby potentially facilitating the entry and spread of alien weed species. This phenomenon, together with the invasive expansion of existing weeds that more successfully coevolve and adapt to the new environment, might exert an adverse effect on biodiversity. In-depth knowledge of weed seed dispersal, survival, and germination mechanisms is therefore essential for effective and eco-compatible management of the weed phytocoenoses present in the agroecosystem in order to promote a rational trade-off between agricultural productivity and environmental protection.