4

4.1 INTRODUCTION

All multicellular eukaryotes which are photosynthetic autotrophs are grouped under Kingdom Plantae. Plants have cellulose in their cell wall, and store their carbohydrates as starch. We shall be studying about the major plant Phyla and characteristics of their plant representative.

4.2 OBJECTIVES

After completing the lesson, you will be able to:

list the major divisions of the Kingdom Plantae;

list the important characteristics of division Bryophyta;

differentiate between mosses and ferns;

Classify Trachaeophyta;

list the important characteristics of phylum pteridophyta with common examples;

state the characteristics of Divisions Spennatophyta and Gymnusperms' with their common examples;

list important characteristics ofangiosperms;

Differentiate between angiosperms and gymnosperms, dicot and monocot plants;

list some common monocot and dicot families with their charac-teristics ||Sand given common examples of family Brassicaceae, Poaceae and Papilionaceae.

4.3 MAIN DIVISIONS OF KINGDOM PLANTAE (PLANTS)

4.4 BRYOPHYTA (BRYOPHYTES)

Bryophytes are amphibians of plants as they complete their life cycle in |

water and on land.

There are two main types of bryophytes:-

In both type of bryophytes, the main plant body is a gametophyte, which bears the sex organs. The male sex organs are antheridia and female sex organs are archegonia. The gametes are produced in the sex organs. Therefore the plant body of liverwort and moss plant is a gametophyte. Male and female gametes fuse to give rise to a body which develops into a sporophyte. Sporophyte remains attached to gametophyte. The sporophyte bears spores. The spores germinate to give rise to a gametophyte again.

itotrophs

Gametophyte	Gamete producing plants
Sporophyte	Spore producing plants

The two phases gametophyte and sporophyte, alternate in bryophytes. The phenomenon is called Alternation of generations.

Bryophytes are amphibians of plant kingdom. In Bryophytes saprophyte remains attached to game tophyte.

4.5 COMPARISON OF GAMETOPHYTIC AND SPOROPHYTIC PHASE

Gametophytic	Sporophytic
1. Haploid phase	Diploid phase
2. Has sex organs	Has spore producing body
3. Produces gametes	Produces spores
4. Gametes are produced by mitosis	Spores are produced by meiosis
5. Dominant phase occupies most of the life period	Short lived phase

The bryophytes are pioneers of vegetation, i.e. they are first ones to grow on various habitats like rock, lava, sand, water etc.

They are the sources of food for fish and birds etc.

Bryophytes grow well in cool and humid places.

4.6 PTERIDOPHYTA (PTERBDOPHYTES)

Look at Fig. 4.2. A fern plant is a pteridophyte. It's body is divided into i 3 root, stem and leaves, but does not bear any flower or seed.

The plant body contains vascular tissue-xylem and phloem. They are therefore | -grouped under trachaeo-phyta. Pteridophytes are found in gardens, on the hills etc.

On the under surface of the leaves, develop spores producing bodies called Sporangia. As the plant body of pteridophytes produces spores, they are Sporophytes.

The spores germinate mto an independent thallus like body the gametophyte called prothallus. The prothallus bears antheridia and archegonia which produce male gametes and female gametes. The gametes-fuse and zygote develops into a sporophyte. The two phases alternate as in bryophytes.

Gametophyte grows independent of sporophyte.

Pteridophytes have dominant sporophytic phase and short lived gametophytic phase.

4.7 GYMNOSPERMAE (Gk-gymnps-naked, sperma-seed)

Together with flowering plants angiosperms, the gymnosperms form |the group Spermatophyta (sperma-seed; phyte-plant) i.e. Seed producing 1-plants.

Pinus, deodar are common gymnosperms (gymnos-naked sperma-seed.) | The gymnosperms bear seeds, which are exposed on special leaves.

An ovuliferous scale of a cone

(or 3^rd year cone)

Fig 4.3 Pine Tree with Male and Female Cone

Characteristics of Gymnosperms

The adult plant (sporophyte) is tall, woody, perennial tree or shrub. The stem is usually branched, but rarely so in Cycas.

Vascular bundles in stem are arranged in a ring.

Leaves may be dimorphic or of one kind only. Foliage leaves are large and few as in Cycas or small and numerous as in Pinus. Leaves of pine are called needles.

Plants are ever-green, leaves may be simple (as in Pinus) (Fig. 4.3) or compound (as in Cycas).

Gymnosperms bear cones which are always unisexual (either male or female).

Pollen grains are produced by male cones and each has two mail gametes.

Ovules are not enclosed in ovary as in Angiosperms, but are bomf naked on leafy megasporophylls of female cone, so the term gymno' sperms or 'naked seeds' for this group. Male gamete fuses with femal< gamete in the ovule. The ovule then develops into a seed.

Some common Gymnospenns are :

Pine (Pinus), Red Wood (Sequoia), Jumper (Juniperus), Cedar (Cedrus). Many gymnosperms yield timber, resins, turpentine, and many othel products.

4.8 ANGIOSPERMAE

Our most familiar plants like pea, mango, coconut, wheat and rice come under the group called Angiosperms. Their seeds are always enclosed in the fruit (a fruit is a mature ovary).

Look at an angiosperm plant Fig. 4.4

The angiosperms are divided into two groups :

1. Dicotyledons.

2. Monocotyledons.

Look at Fig. 4.5 to study the differences between the two groups.

DIFFERENCES BETWEEN ANGIOSPERMS AND GYMNOSPERMS

Gymnosperms	Angiosperms
Seeds naked as not enclosed in ovary. Bears cones where spores (gametes) develop. 3. Xylem vessels absent.	Seeds enclosed in fruit (a mature ovary). Bears flowers^ where spores (gametes) develop Xylem has both vessels as well as tracheids.

4.10 SOME FAMILIES OF ANGIOSPERMS

Today Angiosperms plants, belong to the most diverse and wide spread members of the Kingdom Plantae.

As in case of all living organisms, Angiosperms too are classified. Flowers offer a large number of characters and so they are used for grouping of plants into different families.

Within each family are included plants which show similarities in

organization of various parts of flower.

We shall study only three families:

1. Brassicaceae/Crucifer.'e - Mustard family

2. Papilionaceae - Pea family

3. Poaceae/Graminae - Grass family

Family Brassicaceae : A dicotyledonous family.

The plants are herbs, with flowers having cruciform petals i.e. petals arranged like a cross. (Fig. 4.6)

There are 6 stamens (male parts) - 2 outer short and 4 inner long (Tetradynamous).

WHAT YOU HAVE LEARNT

Kingdom Plantae is classified into two divisions i.e. Bryophyta and Trachaeophyta.

Broyophytes are amphibians of plants.

Main plant body ofBryophytes is a gametophyte; sporophyte remains attached to gametophyte.

Main plant body of Pteridophytes is a sporophyte.

Bryophytes and Pteridophytes show alternation of generations

Gymnosperms and Angiosperms are seed producing plants.

In Gymnosperms seeds are naked, whereas in Angiosperms seeds are enclosed in ovary.

Main difference between dicotyledonous and monocotyledonous plants is number of cotyledons.

Angiosperms are classified into families.

Brassicaceae and Papilionaceae are dicot families, whereas Poaceae is a monocot family.

TERMINAL QUESTIONS

1. List the main groups of kingdom Plantae.

2. Give me two main types ofBryophytes.

3. Differentiate between gametophyte and sporophyte.

4. Define alternation of generations.

5. Why are Pteridophytes grouped under Trachaeopyta?

6. Differentiate between Angiosperms and Gymnosperms.

7. Give three main differences between dicot and monocot plants.

8. Name three families of Angiosperms giving one character of each family.

CHECK YOUR ANSWERS

4.1 1. They complete their life cycle in water and land.

2. Alternation of gametophytic phase with sporophytic.

3. Antheridia and Archegonia

Cool and humid place.

4.2 1. (i) Sporophytic

(ii) Spores

2. They have vascular tissues

Antheridia and Archegonia

4.3 1. Naked seeds

2. Cycas and Pinus

Timber, resins

4.4 1. Brassicaceae/Papilionaceae. Poaceae.

2. 10, 6

3. (i) Oryza sativa

(ii) Raphanus sativus

(iii) Brassica campestris

4. Ovary