Weeds are classified according to their similarities and differences which are effective in formulating an effective control program. These are according to their: a) Life Cycle, b) Gross Morphological Features, c) Body Texture, d) Habit-Manner of Growth, and e) Habitat.
According to their Life Cycle, weeds are classified as annual, or perennial. Annual weeds complete their life cycle in one season and reproduce mainly by seeds while perennial weeds live for more that one season and reproduce vegetatively and by seeds. They can either be simple perennials that reproduce only by seeds or creeping perennials that reproduce by seeds and by vegetative propagules.
Weeds are classified according to their Morphological Features can be grass, sedge, or broadleaf. Grasses have stems called culms that are cylindrical and has has a well defined nodes and internodes. Their leaves arise alternately in two rows. Ligules can be observed in grasses. Sedges on the other hand have triangular culms and does not have ligules. Their nodes and internodes are indistinct which are located at the basal part of the culm. Broadleaved weeds are characterized as having expanded leaves. They can either be monocots or dicots.
We classify weeds as herbaceous, woody, or vine according to the general appearance of their stems. Their habit of growth can be erect-those that have an upwight growth, prostrate-lying flat on the ground, or twining-those that are climbing or clinging for support.
Weeds can be aquatic-those living in water, terrestrial-grows on land, or aerial-or epiphytes growing in air or attached to trees or other support, according to their habitat.
February 1, 2008
January 28, 2008
Insect Characteristics
There are 725,000 insect species recorded in 1954. This is three times more that all other animals combined. The recent number of insect species known today is close to a million. Insects have lived on earth for about 350 million years compared to a less that 2 million years for man. They evolved and developed unusual morphological features, habit or behavior and unique characteristics to survive in any type of habitat.
Here are some insect characteristics that made them a successful group of arthropods:
1. Insects have hard and impervious body cover which is called the exoskeleton.
2. Insects possess wings that help them avoid predatory enemies, unfavorable conditions, and in finding food and mate.
3. Insects have high rate of reproduction. They have short developmental period and have high fecundity, meaning, several eggs are being laid by the mother.
4. Insects have a small size. This made them capable to complete development and reproduction with small amount of food.
5. Insects have varied developmental stages and habits.
6. Insects have a great capability of adaptation which allowed them to survive for a very long period of time.
7. Insects have highly varied habits and behavior.
These characteristics have made the insects of today survive millions of years ago.
Here are some insect characteristics that made them a successful group of arthropods:
1. Insects have hard and impervious body cover which is called the exoskeleton.
2. Insects possess wings that help them avoid predatory enemies, unfavorable conditions, and in finding food and mate.
3. Insects have high rate of reproduction. They have short developmental period and have high fecundity, meaning, several eggs are being laid by the mother.
4. Insects have a small size. This made them capable to complete development and reproduction with small amount of food.
5. Insects have varied developmental stages and habits.
6. Insects have a great capability of adaptation which allowed them to survive for a very long period of time.
7. Insects have highly varied habits and behavior.
These characteristics have made the insects of today survive millions of years ago.
January 25, 2008
Weeds
Weeds are important component of the agroecosystem. They always grow with crops and its economic impact is greatest in agriculture. It is an important factor to consider in the management of land and water resources and dictate many of the crop production practices and management decision in growing crops.
We can defined a weed as a plant unwanted at a particular time and place and can do more harm than good under such time and place. The concept of a weed is man-made. One man's crop may be another man's weed. Of the 300,000 species of angiosperms, 10% 30,000 species behave as weed 99% of the time.
Weeds can be characterized to have a rapid vegetative growth, reproduce rapidly and mature early, be very prolific and produce plenty of seeds, have the ability to survive and adapt to adverse conditions, be adapted to crop competition, and whose propagules possess dormancy or can be induced to become dormant under favorable conditions.
The last characteristic of the weed is the reason why most of the empty lots we see today are populated with weeds. One year of planting would equal to seven years of weeding.
We can defined a weed as a plant unwanted at a particular time and place and can do more harm than good under such time and place. The concept of a weed is man-made. One man's crop may be another man's weed. Of the 300,000 species of angiosperms, 10% 30,000 species behave as weed 99% of the time.
Weeds can be characterized to have a rapid vegetative growth, reproduce rapidly and mature early, be very prolific and produce plenty of seeds, have the ability to survive and adapt to adverse conditions, be adapted to crop competition, and whose propagules possess dormancy or can be induced to become dormant under favorable conditions.
The last characteristic of the weed is the reason why most of the empty lots we see today are populated with weeds. One year of planting would equal to seven years of weeding.
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