Q6. Enlist the different ways of dispersal of seeds. Give examles of
each.
Answers
Wind dispersal (anemochory) is one of the more primitive means of dispersal. Wind dispersal can take on one of two primary forms: seeds can float on the breeze or alternatively, they can flutter to the ground.[20] The classic examples of these dispersal mechanisms, in the temperate northern hemisphere, include dandelions, which have a feathery pappus attached to their seeds and can be dispersed long distances, and maples, which have winged seeds (samaras) and flutter to the ground. An important constraint on wind dispersal is the need for abundant seed production to maximize the likelihood of a seed landing in a site suitable for germination. Some wind-dispersed seeds, such as those of the dandelion, can adjust their morphology in order to increase or decrease the rate of germination.[21] There are also strong evolutionary constraints on this dispersal mechanism.
Water
Many aquatic (water dwelling) and some terrestrial (land dwelling) species use hydrochory, or seed dispersal through water. Seeds can travel for extremely long distances, depending on the specific mode of water dispersal; this especially applies to fruits which are waterproof and float on water.
Answer:
Seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their propagules, including both abiotic vectors such as the wind and living (biotic) vectors like birds. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time. The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions. There are five main modes of seed dispersal: gravity, wind, ballistic, water, and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus. Dispersal involves the letting go or detachment of a diaspore from the main parent plant.[1]
Explanation:
Long distance
Autochory
Gravity
Ballistic dispersal
Allochory
Wind
Wind dispersal of dandelion seeds
Entada phaseoloides – Hydrochory
A special review for oceanic waters hydrochory can be seen at oceanic dispersal.
Animals
The small hooks of the surface of a bur enable attachment to animal fur for dispersion.
Humans
Dispersal by humans (anthropochory) used to be seen as a form of dispersal by animals. Its most widespread and intense cases account for the planting of much of the land area on the planet, through agriculture. In this case, human societies form a long term relationship with plant species, and create conditions for their growth.
Recent research points out that human dispersers differ from animal dispersers by having a much higher mobility, based on the technical means of human transport.[38] On the one hand, dispersal by humans also acts on smaller, regional scales and drives the dynamics of existing biological populations. On the other hand, dispersal by humans may act on large geographical scales and lead to the spread of invasive species.[39]
Humans may disperse seeds by many various means and some surprisingly high distances have been repeatedly measured.[40] Examples are: dispersal on human clothes (up to 250 m),[41] on shoes (up to 5 km),[38] or by cars (regularly ~ 250 m, singles cases > 100 km).[42] Seed dispersal by cars can be a form of unintentional transport of seeds by humans, which can reach far distances, greater than other conventional methods of dispersal.[43] Cars that carry soil are able to contain viable seeds, a study by Dunmail J. Hodkinson and Ken Thompson found that the most common seeds that were carried by vehicle were, Plantago major, Poa annua, Poa trivialis, Urtica dioica and Matricaria discoidea.[43]
Deliberate seed dispersal also occurs as seed bombing. This has risks, as unsuitable provenance may introduce genetically unsuitable plants to new environments.
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