Agriculture
Within the angiosperms (flowering plants), two classes have been traditionally recognized by botanists: monocots and dicots. The terms connote differences between these groups? seed embryos. The recently introduced class, eudicots, literally meaning ?true dicots,? is increasingly used in place of the term ?dicots.?
Of the large number of plant species which currently inhabit the earth, most (about one-quarter million) are angiosperms, plants that reproduce by means of flowers. The famous naturalist Charles Darwin called angiosperms ?an abominable mystery.?
Even today, much remains to be learned about the ancestry of angiosperms and when and where angiosperms first appeared. It is now believed that the first extant angiosperm is a single species of the genus Amborella. This plant, found on an island in the South Pacific, is a shrub with cream-colored flowers.
All angiosperms are assigned to the phylum Anthophyta. Within this phylum, considerable diversity occurs. However, two large lineages have traditionally been recognized: class Monocotyledones (monocots) and class Dicotyledones (dicots).
Themonocots include grasses, cattails, irises, lilies, orchids, and palmtrees. The dicots include the vast majority of seed plants: herbs, vines, shrubs, and most trees (cone-bearing trees are not angiosperms).
The terms ?monocot? and ?dicot? reflect the number of cotyledons, one or two, respectively, possessed by seeds of the plants. Acotyledon is the central portion of a seed embryo to which the epicotyl (immature shoot) and radicle (immature root) are attached.
However, one need not examine the seed of a particular flowering plant in order to assign it to the correct class. Fortunately, each angiosperm possesses a ?syndrome? of features, any one of which may be used for the purpose of classification.
Vegetative Parts
Monocots have leaves with parallel veins: The large, easily visible veins are parallel and extend the length of the (usually) linear leaves. In contrast, leaves of dicots are net-veined: The veins branch repeatedly as they extend into the various portions of the leaf.
Vascular bundles (clusters of conducting cells) within stems of monocots are scattered, in contrast to those of dicots, which are arranged into a cylinder. These are best seen in a cross-section of the root. Furthermore, stems of monocots rarely produce wood, whereas those of many dicots (trees and shrubs) increase their diameter yearly, as wood accumulates within them.
Reproductive Parts
Flowers of monocots typically have their parts arranged in threes and are said to be ?3-merous.? An example would be a lily flower, which has these parts (designated fromthe outside toward the center of the flower): three sepals, three petals, six stamens, and one pistil.
Flowers of dicots have parts arranged in fours or fives. Also, pollen grains produced by flowers of monocots each have one pore in the outer covering, as compared to three pores in the case of dicot pollen grains.
Thus, it is apparent that nearly any part of a flowering plant can be used to place it into the correct subgroup of angiosperms. However, it is the flowers and leaves that are most easily considered (not requiring microscopic examination).
New Interpretations
Like all areas of science, botany is subject to modification and reinterpretations as a result of the accumulation of new information. One group of plants traditionally considered to be dicots, the magnoliids, have long been problematic. They have some features of dicots, but their floral parts are free (unattached to one another) and arranged spirally.
Also, they produce pollen grains, each of which has only a single pore. These features are characteristics of monocots. These traits have thus caused thosewho study angiosperms to place them into a new, third category, the classmagnoliids.
This most primitive group of angiosperms is thought to be ancestral to both of the other classes. The southern magnolia, Magnolia grandiflora, with its huge, white flowers, is a good example of this class. The name eudicots is applied to the still-large group that includes the remainder of the dicots.
- Angiosperm Evolution
AngiospermAngiosperms (flowering plants) appeared about 130 million years ago and today dominate the plant world, with approximately 235,000 species. In early Devonian-age rocks, approximately 363- 409 million years old, fossils of simple vascular and...
- Angiosperm Plant Formation
Angiosperm Plant FormationAngiosperms are flowering plants. Their formation entails development from embryo to seed, through germination to seedling, and finally to mature plant. The life cycle of angiosperms (flowering plants) involves an alternation...
- Angiosperms
AngiospermsThe name "angiosperms" has long been used by botanists to refer to the flowering plants, a group of approximately 235,000 species. All angiosperms are members of the phylum Anthophyta. The name "angiosperm" is actually derived from two Greekwords,...
- Flower Types
Yellow hibiscus flower The flower is the most distinctive feature of the phylum Anthophyta, commonly referred to as angiosperms or flowering plants, and is responsible in making them the most dominant, diverse, and widespread of all groups of plants....
- Monocotyledones
MonocotyledonesThe Monocotyledones, or monocots, are a large and very distinctive class of angiosperms or flowering plants, phylum Anthophyta, consisting of some 133 families, 3,000 genera, and 65,000 species. Monocotyledones form one of the two major...
Agriculture
Monocots vs Dicots
Of the large number of plant species which currently inhabit the earth, most (about one-quarter million) are angiosperms, plants that reproduce by means of flowers. The famous naturalist Charles Darwin called angiosperms ?an abominable mystery.?
Even today, much remains to be learned about the ancestry of angiosperms and when and where angiosperms first appeared. It is now believed that the first extant angiosperm is a single species of the genus Amborella. This plant, found on an island in the South Pacific, is a shrub with cream-colored flowers.
All angiosperms are assigned to the phylum Anthophyta. Within this phylum, considerable diversity occurs. However, two large lineages have traditionally been recognized: class Monocotyledones (monocots) and class Dicotyledones (dicots).
Themonocots include grasses, cattails, irises, lilies, orchids, and palmtrees. The dicots include the vast majority of seed plants: herbs, vines, shrubs, and most trees (cone-bearing trees are not angiosperms).
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The terms ?monocot? and ?dicot? reflect the number of cotyledons, one or two, respectively, possessed by seeds of the plants. Acotyledon is the central portion of a seed embryo to which the epicotyl (immature shoot) and radicle (immature root) are attached.
However, one need not examine the seed of a particular flowering plant in order to assign it to the correct class. Fortunately, each angiosperm possesses a ?syndrome? of features, any one of which may be used for the purpose of classification.
Vegetative Parts
Monocots have leaves with parallel veins: The large, easily visible veins are parallel and extend the length of the (usually) linear leaves. In contrast, leaves of dicots are net-veined: The veins branch repeatedly as they extend into the various portions of the leaf.
Vascular bundles (clusters of conducting cells) within stems of monocots are scattered, in contrast to those of dicots, which are arranged into a cylinder. These are best seen in a cross-section of the root. Furthermore, stems of monocots rarely produce wood, whereas those of many dicots (trees and shrubs) increase their diameter yearly, as wood accumulates within them.
Reproductive Parts
Flowers of monocots typically have their parts arranged in threes and are said to be ?3-merous.? An example would be a lily flower, which has these parts (designated fromthe outside toward the center of the flower): three sepals, three petals, six stamens, and one pistil.
Flowers of dicots have parts arranged in fours or fives. Also, pollen grains produced by flowers of monocots each have one pore in the outer covering, as compared to three pores in the case of dicot pollen grains.
Thus, it is apparent that nearly any part of a flowering plant can be used to place it into the correct subgroup of angiosperms. However, it is the flowers and leaves that are most easily considered (not requiring microscopic examination).
New Interpretations
Like all areas of science, botany is subject to modification and reinterpretations as a result of the accumulation of new information. One group of plants traditionally considered to be dicots, the magnoliids, have long been problematic. They have some features of dicots, but their floral parts are free (unattached to one another) and arranged spirally.
Also, they produce pollen grains, each of which has only a single pore. These features are characteristics of monocots. These traits have thus caused thosewho study angiosperms to place them into a new, third category, the classmagnoliids.
This most primitive group of angiosperms is thought to be ancestral to both of the other classes. The southern magnolia, Magnolia grandiflora, with its huge, white flowers, is a good example of this class. The name eudicots is applied to the still-large group that includes the remainder of the dicots.
- Angiosperm Evolution
AngiospermAngiosperms (flowering plants) appeared about 130 million years ago and today dominate the plant world, with approximately 235,000 species. In early Devonian-age rocks, approximately 363- 409 million years old, fossils of simple vascular and...
- Angiosperm Plant Formation
Angiosperm Plant FormationAngiosperms are flowering plants. Their formation entails development from embryo to seed, through germination to seedling, and finally to mature plant. The life cycle of angiosperms (flowering plants) involves an alternation...
- Angiosperms
AngiospermsThe name "angiosperms" has long been used by botanists to refer to the flowering plants, a group of approximately 235,000 species. All angiosperms are members of the phylum Anthophyta. The name "angiosperm" is actually derived from two Greekwords,...
- Flower Types
Yellow hibiscus flower The flower is the most distinctive feature of the phylum Anthophyta, commonly referred to as angiosperms or flowering plants, and is responsible in making them the most dominant, diverse, and widespread of all groups of plants....
- Monocotyledones
MonocotyledonesThe Monocotyledones, or monocots, are a large and very distinctive class of angiosperms or flowering plants, phylum Anthophyta, consisting of some 133 families, 3,000 genera, and 65,000 species. Monocotyledones form one of the two major...