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Magnoliopsida: A Class of Flowering Plants


Magnoliopsida: A Class of Flowering Plants

Magnoliopsida is a botanical name for a class of flowering plants that have two cotyledons (embryonic leaves) in the seed, which usually appear at germination. The name is derived from the genus Magnolia, the Latinized name of Pierre Magnol, a French physician and botanist (1638-1715). The suffix is derived from the Greek for that which resembles (opsis -οψισ). Together, they mean that which resembles a Magnolia.

Magnoliopsida is also known as dicotyledons or dicots, and it includes about 300,000 species of plants that are diverse in morphology, ecology and life history. Some examples of dicots are roses, sunflowers, beans, peas, oaks, maples and magnolias. Dicots have several characteristics that distinguish them from monocots, another class of flowering plants that have one cotyledon in the seed. Some of these characteristics are:

  • Dicots have net-like leaf veins, while monocots have parallel leaf veins.
  • Dicots have flower parts in multiples of four or five, while monocots have flower parts in multiples of three.
  • Dicots have vascular bundles arranged in a ring in the stem, while monocots have vascular bundles scattered throughout the stem.
  • Dicots have a tap root system with lateral secondary roots branching out from the primary root, while monocots have a fibrous root system with many thin roots.
  • Dicots have a vascular cambium that produces secondary xylem and phloem in woody plants, while monocots usually do not have a vascular cambium and thus do not undergo secondary growth .

Magnoliopsida is a large and diverse class of plants that has many economic and ecological importance. They provide food, fiber, medicine, ornamental and timber products for humans and animals. They also play a vital role in maintaining the biodiversity and ecosystem functions of the planet.

One of the subclasses of Magnoliopsida is Magnoliidae, which contains the most primitive and ancestral dicots. This subclass includes the order Magnoliales, which contains the family Magnoliaceae, the type family of the class. Magnoliaceae is one of the oldest flowering plant families, dating back to about 100 million years ago. It has about 220 species of trees and shrubs that are mostly tropical and subtropical. They have large and fragrant flowers with many tepals (undifferentiated petals and sepals) and stamens. They also have aggregate fruits that consist of many carpels (ovule-bearing units) that split open at maturity. Some examples of magnoliaceae are magnolias, tulip trees and bay laurels.

Another subclass of Magnoliopsida is Rosidae, which contains the largest and most diverse group of dicots. This subclass includes about 70,000 species of plants that are distributed in almost all habitats and climates. They have a wide range of morphological and physiological adaptations that enable them to survive in various environmental conditions. Some of the common characteristics of rosids are:

  • They have flowers with four or five petals, sepals, stamens and carpels.
  • They have fruits that are either dry (such as nuts, pods and capsules) or fleshy (such as berries, drupes and pomes).
  • They have leaves that are usually simple, alternate and stipulate (with small leaf-like structures at the base of the petiole).
  • They have secondary metabolites that are often aromatic, bitter or toxic, such as tannins, flavonoids and alkaloids.

Some of the major orders of rosids are Fabales (legumes), Rosales (roses), Malpighiales (euphorbias), Brassicales (mustards), Malvales (mallows), Sapindales (citrus) and Myrtales (myrtles).

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