Wednesday, March 16, 2011

Monocots and Dicots

There are two major groups of flowering plants that are easily recognized by their cotyledons. Cotyledons are seed leaves that emerge when germination occurs.

 A cotyledon is a significant part of the embryo within a plant seed. Upon germination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify angiosperms (flowering plants).

Species with one cotyledon are called monocotyledons or monocots and species with two embryonic leaves are termed dicotyledons or dicots.

There are approximately 59,300 species within the monocot group. The largest family in this group, and in the flowering plants as a whole, are the orchids (family Orchidaceae) with more than 20,000 species.

Many plants cultivated for their blooms are also from the monocot group, notably lilies, daffodils, irises, amaryllis, orchids, cannas, hemerocallis, bluebells and tulips.

In agriculture the majority of the biomass produced comes from monocots. The true grasses are the most economically import family in this group. These include all true grains (rice, wheat, maize, etc.), the pasture grasses, sugar cane and the bamboos.

Other important monocot families are the palm family (Arecaceae), banana family (Musaceae), ginger family (Zingiberaceae) and the onion family (Alliaceae).
Many monocots are herbaceous and do not have the ability to increase the width of a stem.

One of the most noticeable traits is that a monocot's flower is trimerous, with the flower parts in threes or in multiples of three. That is to say, a monocotyledon's flower typically has three, six, or nine petals. Many monocots also have leaves with parallel veins.

Monocots evolved from a single ancestor, and are younger than dicots, from which they probably branched off, as recent genetic research has shown. They evolved 100-120 million years ago, shortly after the flowering plant explosion.

There are approximately 199,350 species within the dicotyledon group. Most of the fruits, vegetables, spices, roots and tubers which constitutes a very important part of our daily diet, are classified as dicots.

In addition, all legumes, beverages such as coffee and cocoa, and a great variety of flowers, oil seeds, fibers, and woody plants belong to the dicot group.

Dicot plants range from tiny plants to tremendous trees; fleshy succulents to delicate herbs that dry out almost as soon as they're picked; large and complex flower heads to tiny flowers that barely deserve the name; annuals and perennials; deciduous and evergreen. Each plant can be described with 100 features including size, shape, color, and features of the entire plant, leaves, flowers, and fruit.

Around 300 families of flowering plants are currently identified as Dicots. The most prominent herb and shrub families are sun-flower family consisting of daisies, asters, thistles and dandelions. All have compound flower heads. While it appears to be a single flower, closer examination reveals that the head is composed of many separate flowers; tiny five-petal disk flowers‘ in the center and/or single petalled ray flowers‘ around the outside. Dandelions have only ray flowers, thistles and coyote brush have only disk flowers, sunflowers and daisies have both.

Also included in the dicots are the pea family, geranium family and the heath family. Buttercup, snapdragons, mustard, poppy, evening primrose, mint, mallow, borage, and phlox are also in this group.

**Article reprinted from The BC Council of Garden Clubs, The Bulletin, March/April 2011**

An example of a Dicot
Venus fly trap
An example of a Monocot
Coconut Tree

1 comment:

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