Angiosperms or flowering plants are the most dominant group of the
vascular plant world. The term angiosperm was devised to describe one of
the most definitive elements of flowering plants, namely the enclosure
of the potential seeds within a hollow ovary. The angiosperms are
considered to be advanced as compared with the gymnosperms and other
tracheophytes (plants and trees). Flowering plants occur in a wide range
of habitats including both salt and fresh water. The basic food supply
of the world is derived from the seeds and fruits of angiosperms (rice,
wheat, corn) and fibers, wood, drugs, and other products of great
economic value.
The studies by John Ray in the 1700's on the structure of seeds led
him to discover the difference between monocotyledon (monocots) and
dicotyledon (dicots) plants. There are estimated to be about 165,000
different types of dicots and 55,000 types of monocots.
Monocots have only one cotyledon, dicots have two cotyledons. A
cotyledon contains stored food and serves as a food reservoir. Aside
from the difference between the seeds of monocots and dicots there are
other different structures that separate monocots and dicots. Monocots
have long, narrow leaves with parallel veins (such as grasses.) The
parts of monocot flowers are arranged in threes or in multiples of
three. Dicots have broad leaves with branched veins. The parts of dicot
flowers are arranged in fours and fives or multiples of fours and fives.
Although the distinction between monocots and dicots is not always as
sharp and clear as once thought, it is a useful taxonomic grouping.
PROCEDURE:
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In this lab students will differentiate between monocot and dicot
seeds. Make sure you soak the seeds in water one day prior to the
laboratory session. The directions are written on the lab sheet.
Students should be instructed to examine the seeds carefully and to draw
exactly what they see.
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An endosperm is the nutritive tissue in the developing seeds of
angiosperms. A cotyledon is the seed or first leaf of angiosperms and
gymnosperms. A bean and a peanut are dicots; corn is a monocot.
