diversity of pteridophytes

BIO102: Plant Diversity

OLABISI ONABANJO UNIVERSITY Bup Oyesiku PhD

www.bupoyesiku.net ~ 1 ~ Department of Plant Science

DIVERSITY OF PTERIDOPHYTES

Fertilization

A

D B C

G

A A

E

F

http://www.bupoyesiku.net/




Contents Topic: Diversity of Pteridophytes ....................................................................................................... 3

Objectives ......................................................................................................................................... 3

Reading Assignment .......................................................................................................................... 3

Lecture .............................................................................................................................................. 3

Introduction ...................................................................................................................................... 4

Main Content .................................................................................................................................... 4

Background of Pteridophytes ......................................................................................................... 4

Reproduction in Pteridophytes ...................................................................................................... 4

Vegetative reproduction ............................................................................................................ 4

Asexual reproduction ................................................................................................................. 5

Sexual reproduction ................................................................................................................... 5

Classification of Pteridophytes ....................................................................................................... 6

Characteristics of Pteridophytes .................................................................................................... 7

Diversity of Forms in Pteridophytes ............................................................................................... 7

Habitats of Pteridophytes .............................................................................................................. 9

Ecology of Pteridophytes ................................................................................................................... 9

Economic uses of Pteridophytes ........................................................................................................ 9

Conclusion ....................................................................................................................................... 10

Summary ......................................................................................................................................... 10

References/Further readings/Links .................................................................................................. 10

Test Yourself Questions (TYQ).......................................................................................................... 11





Topic: Diversity of Pteridophytes

Objectives

In this lecture we will learn the followings:

Clear idea of the features that separate Pteridophytes from other plants

Skills in identifying them in our environment

Importance of the Pteridophytes

Contributions to our lives

Reading Assignment

In addition to the discussion in this lecture you should read current textbooks in the

library and visit: ilearn.bupoyesiku.net for the online lecture.

Lecture

In previous lecture we discussed about non-vascular green plant bryophytes. In our

earlier lectures, you have learnt about the characteristics of the members of algae,

lichen, fungi and monera. In our today’s lecture, we are going to be discussing the

most advanced member of the spore plants, the Pteridophytes. You will be taken to

the next level of understanding biodiversity with particular reference to vascular spore

plants. Pteridophyte is the first land vascular photosynthetic plants. They differ from

angiosperm because their leaves have apical meristem that continues to grow in

length for some time. And from other spore producing plant by bearing spores on the

lower surface. They are important not only for academic teaching, but also for their

unique ferns and allies for aesthetic beautification of our environment. Furthermore,

your knowledge of the field (Pteridology) will makes you more conscious of their

abundance and important roles to humans. Especially for those of you that are going

to become famous Pteridologists, as well as those that require the knowledge in their

field of study.





Introduction

Pteridology is the study of Pteridophytes. Like bryophytes and other non-vascular

plants they primarily trap solar energy directly from the atmosphere and convert it to

food. They form an advance producer in terrestrial food web of a typical ecosystem.

Main Content

Background of Pteridophytes

Pteridophytes are the first vascular plant with xylem and phloem. They reproduce by

spores. Thus they are called vascular cryptogams. It is important to know that the seed

plants are probably descendants of certain extinct members of pteridophytes,

Progymnosperms. It is therefore obvious that some members are polyphyletic, from

more than one ancestor. In addition, pteridophytes, probably evolved from the

advanced green algae at about the same time as the first vascular seed plants

because they both share multicellular sex organs, but the green algae lack vascular

tissue.

Reproduction in Pteridophytes

Vegetative reproduction

There are two describable types of vegetative reproduction in pteridophytes. Death of

older portion of rhizome with separation of growing apices. Formation of buds on

leaves, although very rare.





Asexual reproduction

Asexual reproduction occurs in the sporangia of the sporophytes. Spores are gathered

together into a group called sori, borne under the leaves surface. The sporangium form

spore mother cells that meiotically form spores. When mature spores are dispersed

and germinate under favorable conditions they produce a fertile and sterile fronds.

Sexual reproduction

The undersurface of the green heart-shaped gametophyte bears the rhizoids,

antheridia and archegonia (Fig 1.2). Fertilization depends upon a water film. The

resulting embryo sporophytes compose of rhizines (roots), fronds (leaves).

Figure1.1 Fertile Fern frond. Rachis (A), Pinnule (B), Sporangia (C)





Classification of Pteridophytes

Under the current trend in classification, living members of pteridophytes consist of

four major divisions,

Psilotophyta (whisk ferns)

Lycopodiophyta

Sphenophyta and

Pterophyta.

It will interest you to know that Lycopodium spp. (Club moss) share resemblance with

mosses and was in the past mistakenly classified under the Bryophyta.

Figure 1.2 Simplified sexual life cycle in Pteridophyte. Heart-shaped gametophyte (A),

Female gametangium (B), Male gametangium (C), Rhizoid (D), Young sporophyte (E),

Rhizine (F), Spores (G).

Fertilization

A

D B C

G

A A

E

F





Characteristics of Pteridophytes

Most fronds (leaves) are compound, although some are simple

Fertile leaves with spore on the undersurface and sterile leaves

Sporophyte is the dominant plant (independent of gametophyte)

Gametophyte (prothallus) is free living small green heart-shaped plant

Leaves, large and pinnate (fronds)

Circinate vernation or fiddlehead (coiling leaves of young fern)

Stem or rhizome in horizontal underground near soil surface

Spores are house in sacs called sporangium under the leaves

Spore germinate to give filamentous and later green heart-shaped prothallus

Two types of spores (microspores and megaspores)

Diversity of Forms in Pteridophytes

Pteridophytes have two alternating plant bodies the gametophyte and sporophyte.

Gametophyte for the first time in spore producing plants is dependent on the

sporophytes for nutrient supply. The form of the gametophyte is heart-shaped and that

of sporophyte is pinnate compound leaves (fronds). At this point it is important you to

acquire the necessary skill to distinguish between the gametophyte of a thallus

liverwort and that of a pteridophyte.

Club mosses (Lycopodium cernuum): Go online to view the images of club mosses

Spike mosses (Selaginella serpens): Go online to view the images of spike mosses





Quillwort (marsh plant with rosette of tubular leaves, spores at the base): Go online

to view the images of Quillwort

Marattioid fern: Go online to view the images of Marattioid fern

Horsetails (Equisetum spp.): Go online to view the images of horsetail.

Whisk ferns (Psilotophyta): Go online to view the images of Whisk ferns.

Adder’s tongue and Grape ferns (Ophioglossophyta): Go online to view the

images of adder’s tongue and grape ferns.

Leptosporangiate fern (the largest member of ferns): Go online to view the images

of ferns

Figure 1.3 Portion of the shoot of Selaginella serpens collected from the OOU

BIOME, Ago-Iwoye, Nigeria. Lower large leaf (A), Upper small leaf (B), Rhizine (C)

A

B

C





Habitats of Pteridophytes

As you have learnt in previous lectures, Pteridophytes are also native citizen of the

entire world. They grow in great diverse habitats except in the marine Ocean. They

are found in water as well as on land in marshy ground in shady situation. Major groups

of substrate on which Pteridophytes grow are as outline here.

Trees (branch, neck and trunk)

Rock (cracks and crevices)

Decaying woods and plant debris on forest floor

Bare ground

Artificial structures (culvert and old fences)

Ecology of Pteridophytes

Pteridophytes are also important plants in the ecosystem. Pteridophyte members have

functional stomata on the sporophytes. There has never been a record of pteridophyte

fixing nitrogen gas into nitrate for other plant use. Other ecological importance of

Pteridophytes is enumerated here.

Capture and recycling of nutrients wash with rainwater from the atmosphere.

Binding soil surface to prevent erosion

Providing seed beds for higher plants

Highly sensitive to habitat disturbances

Poor indicators of atmospheric pollution

Economic uses of Pteridophytes

Besides the ecological role, pteridophytes have great economic and aesthetic values.

Current trend in the use of ferns have stimulated interests in the field of pteridophytes.

Leaves of ferns are traditionally used in floral arrangements. Some of the economic

values are stated here.

Leaf buds (fiddle heads) of some ferns are commercially harvested and canned or

frozen for food





Spores (Club moss) in making gunpowder and to create dramatic lighting effects

because they can easily and quickly ignite.

Spore powder is use to coat inside of rubber gloves to enhance smooth insertion

of fingers and to reduce sweat irritation

The spore powder (club moss) is used in the pharmaceutical industry to coat

tablets to protect them from moisture

The herb is usually referred to as vegetable sulfur

Conclusion

In this last lecture note, you have learnt how to recognize the members of

pteridophytes as a group of spore producing plants.

At the end of this lecture you must have learnt how to recognize, and where to find the

Pteridophytes. Focus on the usefulness, if encouraged, the use of Pteridophytes as

biomonitor of environmental pollution and vegetation disturbances will be a wise

decision. It can alert us of impending danger in our immediate environment.

Summary

Having study this lecture note, you should:

Have some understanding of members of pteridophytes

Have a better idea of the characteristics that separate pteridophytes from other

groups of cryptogams

Be ready to get going with identification of the members on the field

Understanding contributions of pteridophytes to our lives

References/Further readings/Links





Test Yourself Questions (TYQ)

Matric No Department Attendance-Code Session/Student’s Level

AC_______________

Question TRUE FALSE

1. All pteridophytes are non-vascular plants X

2. Pteridophytes are first non-vascular seed plants X

3. Spike moss is a pteridophyte X

4. Progymnosperms is an ancestor of seed plant X

5. Fiddle heads are observed only in ferns X

6. A fern sporophyte is leafy X

7. Fern gametophyte is capable of fixing nitrogen in the soil X

8. Spores in Pteridophyte form future fertile and sterile fronds X

9. Stem of a fern is always visible ground X

10. Sexual organs in fern are found on gametophyte X

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diversity of pteridophytes

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