The flowering plants or Angiosperms are divided into two classes: the Monocotyledons or monocots and the Dicotyledons or dicots. The fundamental difference occurs during development: monocots have one seed leaf or cotyledon while dicots have two. This seemingly small difference separates the two major types of flowering plants, although there are some fuzzy ‘in-between’ species that indicate that both groups arose from a common angiosperm ancestor. The purpose of the seed leaf is to absorb nutrients from the seed to feed the seedling until the plant can produce true leaves that can photosynthesise.
Monocots have a number of common characteristics although there are exceptions to each characteristic. In general monocots have simple leaves with parallel veins. Think of grass leaves. In contrast, dicots have leaves with reticulated veins. Below the ground, monocots have no tap root but instead the roots run out equally in all directions, while many dicots have a dominant tap root. In dicots the roots develop from a single point, the radical, but in monocots, new roots grow from many nodes in the lower part of the stem.
The flowers of monocots are also simple and usually have three petals or multiples of three. Think of Irises or Lilies. Within the male flowers of monocots, the pollen grains have single furrows or pores. In the dicots, the flowers have petals in multiples of four or five and there are usually three furrows on each of the pollen grains. The single furrowed pollen grain is considered to be the more primitive characteristic and lends evidence to the theory that monocots are the older and more primitive of the two groups. Another common monocot characteristics is that the vascular bundles in the stems are scattered around the stem of the plant instead of being grouped in rings. Again the scattered arrangement of the monocots is considered to be the more primitive condition.
Monocots do not develop woody tissues or bark, so for the most part they are small and grass-like, rather than forming trees. Palms, bananas and agaves, which are large monocots, have wood-like structures but not true woody tissue.
So, most monocots are small, herbaceous flowering plants that can be either annuals or perennials. All the grasses are monocots as well as a number of flower families including orchids, lilies, daffodils, irises and bromeliads. Palm trees and banana trees are the biggest and most tree-like of the monocots. Many swamp and water plants are monocots, including pondweeds such as Elodea. The first paper plant, papyrus, belongs to the large bullrush family of monocots. Other families of monocot water plants include the cattails, water hyacinths and duckweeds.
The most important family of monocots is undoubtedly the Poaceae, which includes many of our most important agricultural crops. Wheat and barley, corn and oats, rice, rye and sorghum are all members of this family. It could be said that the change from hunting and gathering to agriculture was dependent on this monocot family. Where would we as a species be without wheat and rice? Probably not living in cities with modern lifestyles and depending on large scale production of these crops for the bulck of our food.
Monocots are generally small but they are not insignificant. Some of our most important food crops and our most beautiful flowers belong to this great class of flowering plants.
References: http://www.ucmp.berkeley.edu/glossary/gloss8/monocotdicot.html http://www.bridgewater.edu/~lhill/Monocot%20families.htm
