A weed is defined as a plant of its proper place or where it is not required. A weed has more potential than the crop, compete with the crop, seed formation and distribution is before the seed and fruit production from the crop.
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| Cotton field infested with Cynodon dactylon and other weeds |
Here are the few characteristics which must be present in any plant to call them infestation and problematic for the crop (because there are some cropping systems such as relay cropping and intercropping where 2,3 crops are in the same field.)
IDEAL CHARACTERISTICS OF WEED
1. They have ability to grow well under many environmental conditions.
2.Rapid growth rate both in vegetative and flowering stage.
3.Cross-pollination is very common which enable new genetic recombination better suited to the environment.
4. The seed production continues till the condition remains favorable.
5. Self-compatibility but not complete autogamy or apomixy.
6. Greater longevity of the seeds.
7. Discontinuous germination.
8.Bulk of seeds are produced under the favorable environmental conditions.
9.The plants have modification for short and long distance seed dispersal.
10. Vegetative reproduction is vigorous in case of perennial weeds. They can even grow from fragments uprooted or cut weeds.
11. The perennial weeds cannot be easily uprooted from the field.
12. They also produce specific plant chemicals (allochemicals and phytochemicals) in the ground for competing the crop plants.
Apomixy is defined as total limitation of sexual reproduction which greatly reduces the chances of new genetic combinations.
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