DISSEMINATION / DISPERSAL OF WEEDS

DISSEMINATION / DISPERSAL OF WEEDS

  • A plant seed is a unique genetic entity, a biological individual. However, a seed is in a diapause state, an essentially dormant condition, awaiting the ecological conditions that will allow it to grow into an plant, and produce its own seeds.
  • Seeds must therefore germinate in a safe place, and then establish themselves as a young seedling, develop into a juvenile plant, and finally become a sexually mature adult that can pass its genetic material on to the next generation.
  • The chances of a seed developing are generally enhanced if there is a mechanism for dispersing to an appropriate habitat at some distance away from the parent plant.
  • The reason for dispersal is that closely related organisms have similar ecological requirements. Obviously, competition with the parent plant will be greatly reduced if its seeds have a mechanism to disperse some distance away. Their ability to spread and remain viable in the soil for years makes eradication nearly impossible.
  • Seeds have no way to move on their own, but they are excellent travellers. Plants have evolved various mechanisms that disperse their seeds effectively.
  • Many species of plants have seeds with anatomical structures that make them very buoyant, so they can be dispersed over great distances by the winds.
  • In the absence of proper means of their dispersal, weeds could not have moved from one country to another.
  • An effective dispersal of weed seeds and fruits requires two essentials a successful dispersing agent and an effective adaptation to the new environment.

There are two ways of looking at weed seed dispersal:
  • The expanding range and increasing population size of an invading weed species into a new area
  • The part of the process by which an established and stabilized weed species in an area maintains itself within that area Dissemination includes two separate processes. They are dispersal (leaving mother plant) and post-dispersal events (subsequent movement). Dispersal of seed occurs in 4 dimensions viz.
1. Length
2. Width: Land/habitat/soil surface area phenomena
3. Height : soil depth, in the air
4. Time: shatters immediately after ripening (or) need harvesting activity to release seed

Last modified: Wednesday, 7 March 2012, 5:40 AM