DIVISIONS AND CLASSES OF KINGDOM PLANTAE

Learning Objectives

After studying or reading this, you should be able to:

1. List the major phyla of kingdoms protoctista and fungi and describe their major characteristics.

2. Outline the major divisions and classes of kingdom plantae.

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The kingdom Plantae has the following phyla. These are Bryophyta; Lycopodophyta; Filicinophyta Coniferophyta; Cycadophyta, Angiospermophyta.



PHYLUM: Bryonhyta (bryophytes)
They are found mainly in damp places. Reproduction are formed in capsule. They have no true roots; no true leaves, true stems and vascular tissues. The aerial parts of their vegetative body consists of stem-like and leaflike structures. They have rhizoids for anchorage. They show alternation of generation with the gametophyll generation being dominant. They are divided into two classes: Hepaticae and Musci.


CLASS: Hepaticae (liverworts)
They have dorsoventrally flattenedgametophyte called thallus (trail on the ground and made up of a sheet of undifferentiated cells). They are usually dichotomously branched. Their rhizoids are unicellular. Spore capsules split into four valves when they burst during dispersal.

Examples are Marchantia; Pellia and Riccia. They are found mainly on damp and shady habitats, on damp rocks and in wet vegetation.
Matchstick: a liverwort



CLASS: Musci (Masses)
The gametophyte is stem-like and erect unlike liverworts. The mosses have multicellular rhizoids. The capsule is covered with operculum (lid). The leaf-like structures are arranged spirally in three rows of similar size. Dispersal of spores involves tooth-like structures called peristome and spares in the spore capsule. Example is Bryum; Brachymenium
Bryum


DIVISION: Lycopodophyta (Clubmosses) They possess true roots, horizontal stems and leaves which are arranged spirally. Leaves are densely arranged on branching stem with sporangia in between. The sporangia are often clustered into upright cones or strobili at the tips of branches. They show alternation of generations with dominant sporophyt generation. Examples include: Lycopodium and Selaginella.
Silaginella


DIVISION: Filicinophyta (ferns)
These plants have true roots; stems and leaves (usually underground with vascular tissue). They are found mainly in damp places. Reproductive spores are formed on the undersides of the fronds. The Sporangia containing spores are grouped into a brown coloured structure called sori on the lower surface of leaves/fronds. The leaves are large and compounded with intricate shape, ”hence, the name fronds. The stems are covered with numerous scales. The leaves /fronds are highly rolled up and uncoiled as they mature. There is alternation of generation with dominant sporophyte generation and gametophyte reduced to small prothallus. Examples: Nephrolopis ; Drycopteris Pteridium.
Nephrolopis



DIVISION: Coniferophyta (conifers)
They are cone bearing plants. Their leaves are needle-like in shape. They have no flowers and fruits; They have true stems, roots and leaves. They possess complex vascular tissue. There is no vessel in xylem but only tracticids.Ovules are not enclosed in ovary (i.e. naked seeds are present). They are good at surviving in dry or cold climates. Most of them keep their leaves throughout the year. Example: Pine
Pine tree



DIVISION: Cycadophyta (cycads) Their leaves resemble palm superficially. They have long compound leaves clustered at the apex of a thick usually short and unbranched stem. There is presence of cones which are borne at the apex of the trunk among the leaves. They lack flowers and fruits. They possess seeds which are exposed and only covered by seed testa (not enclosed in fruits). Example: cycads.
Cycads


DIVISION: Angiospermophyta (Flowering Plants) This division ranges from small herbs to massive trees. They produce flowers in which sporangia, spores and seeds develop. Their seeds borne are enclosed in an ovary. After fertilization, the ovary develops into a fruit containing the seeds. They have true roots, stem and leaves. The xylem of the vascular bundle contains vessels. The female gametophyte is represented only by a reduced embryo sac with eight nuclei. The division is further divided into two classes: (a) Dicotyledoneae (b) Monocotyledoneae


CLASS: Dicotyledoneae Their leaves are broad and have net-like pattern of veins that is reticulate venation. The leaf has petiole and the dorsal and ventral surface are different. The radicle of the embryo develops into a tap root system. Lateral roots also develop from the tap or primary root as secondary root. The embryo has two Seed leaves or cotyledons. Floral parts are in fours or lives or multiples of that. Petals and Sepals are often differentiated, hence, many are insect pollmated. Vascular bundles are arranged in a form of a ring in the stem, with the presence of vascular cambium giving rise to secondary growth. Examples: mango tree; Tridax; Flamboyant tree; beans plant etc.
A dicot plant



CLASS: Monocotyledonae
Their leaves are long and thin and have parallel venation. The leaves have leaf-sheath. The surface of dorsal and ventral sides of the leaf are identical. The adventitious roots from the base of the stem take over from the primary root giving rise to a fibrous root system. The embryo has one seed leaf or cotyledon. Floral parts are usually in three's or multiples of that. The petals and sepals are usually not differentiated and combine to form perianth. The flowers are often man pollinated since they are dull coloured. In the stem, vascular bundles are usually scattered, and vascular cambium is normally absent and hence, there is no secondary growth. The root also lacks vascular cambium.
Examples include: grasses; maize; onion; plantain; bamboo, etc.
Onion plant






We Hope You Have Understood What You Have Just Read.

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To Make Sure You Have Understood, Answer The Questions Below;

DIVISIONS AND CLASSES 0F KINGDOM PLANTAE

1. What are the distinguishing features of each of the following? i. Green alga.
ii. Bryophyte. iii. Pteridophyte.

2. a. Give or state the phylum of a fern. b. State any two observablefeatures to support your conclusion.

3. Outline four characteristics common to all bryophytes.

4. a. State the two classes of angiosperms. b. How are monocotyledonous plants different from dicotyledonous plants?

5. Give reasons why a moss and cassava plant are classified under one kingdom.

6. How are bryophytes different from pteridophytes?

7. Write down two characteristics each of the following groups and give one example of each.
i. Bryophytes. ii. Ferns. iii. Monocotyledons.
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