Monocots, Dicots and Vascular Bundles

The two classes of angiosperms

All flowering plants are divided into two classes called monocotyledons (monocots) and dicotyledons (dicots).

This is based on the number of leaves that grow when the seed first sprouts. These are not true leaves but parts of the embryo that can use the starch stored in the seed while the plant grows large enough to have real photosynthetic leaves.

Common Monocots and Dicots

Orchids, grasses, wheat, and rice are herbaceous or soft stemmed monocots. Bamboo, palms and sugar cane are woody or tough stemmed monocots.

Herbaceous dicots include potatoes, squash, salad greens and legumes. The woody dicots include common trees and shrubs like maples, oaks and roses.

Comparing monocots and dicots

Angiosperms all have the same plant parts but they are differently organized. The roots, stems and leaves are different because of the vascular bundle patterns are different.

Vascular Bundles

All ferns, gymnosperms and angiosperms have vascular bundles. There are two types of vessels in a vascular bundle, xylem and phloem.

Water and dissolved minerals are carried by xylem from the roots up the stems to leaves and flowers.

Phloem carries sugars between plant cells.

Xylem transports water

Xylem is formed from long tracheids that are dead cells. Water moves into xylem in the roots from the soil by osmosis. Water evaporates from the leaves by a process called transpiration, and this pulls more water up the xylem.

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Phloem and sugars

Phloem is formed from sieve tube elements that are living cells. Sugar dissolved in water is moved both up and down the plant by a process called translocation.

Roots

Monocot roots are fibrous and networked.

Dicots have tap roots like the long thick central root seen on dandelions.

Stems

Monocots have scattered vascular tissue and dicots have vascular tissue in an outer ring. Identify the monocot and dicot stems.

Leaf Veins

In stems, monocots have parallel veins in their leaves.

Dicots have a network of veins in their leaves.

Which is the monocot? Dicot?

Flower parts

Monocots usually have the flower parts in multiples of 3, while dicot petals are in multiples of 4 or 5. Figure out which are the monocot flowers.