Pteridophytes Flashcards

1
Q

Pteridophytes

A

Heteromorphic alternation of generations = gametophyte and sporophyte are morphologically and genetically very different

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2
Q

Characteristics of vascular plants

A

Apical meristems – causes primary growth (lengthening of plant), occurs at tips of shoots and roots, produces new leaves and flowers
Lateral meristems – causes secondary growth (widening of plant), occurs at the cambium, produces bark on trees
Two types – seedless and plants that produce seeds
Sporophyte gen is the dominant gen. Lives independently of the gametophyte which is usually small and inconspicuous
Sporophyte has - apical meristem and is usually branched, vascular conducting tissue with xylem and phloem,
Presence of cuticle, stomata and lignified tissue
Roots

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3
Q

Seedless vascular plants

A

= ferns and allies = pteridophytes

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4
Q

Early vascular plants

A

Earliest were simple
First fossil records from Silurian period, approx. 400 Ma
Rhyniophytes – e.g Cooksonia, Rhynia (fossils)
Sporangia produced at ends of branches
Very simple vascular bundles
Epidermis with cuticle
Homosporous = one type of spore

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5
Q

Psilophyta

A

These are simplest, extant vascular plants – e.g Psilotum (found in tropical and subtropical areas = Hawaii, Florida)
Psilotum is similar to the extinct Rhynia, has no roots and no leaves
Upright stem is branched and has small scales
Sporangia are produced on the ends of branches
Gametophyte is unique among vascular plants because it has a vascular system

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6
Q

True ferns

A

In fossil record from the Carboniferous (360 Ma)
11,000 species = biggest group of seedless vascular plants
Diverse in form
Greatest diversity in tropics, many are epiphytes
Less species in temperate regions but many familiar spp.
Most homosporous
Most temperate forms have a rhizome and produce new sets of leaves each year
Adventitious roots produced from the rhizome
Fern leaves – fern fronds have petiole/stripe (stalk) and lamina (leaf). Midrib is a rachis, degree in which leaves are differentiated is useful in identification
Fern rhizomes – rhizomes underground stems

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7
Q

Fern sporangia

A

Sporangia are produced by the sporophyte generation
Some ferns only produce one type of leaf and sporangia are usually produced on the underside of the leaf
Sporangia are clustered together as a sorus, which is often covered by an indusium
Reproduce via spores – sporangia = spore producing structures
Underside of fern leaf contains sori = clusters of sporangia
Other ferns produce two types of leaves – one vegetative (no sporangia) and one fertile (producing sporangia)

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8
Q

Sphenophyta

A

Giant horsetails were part of the Carboniferous flora e.g Calamites
Modern horsetails much smaller
Underground rhizome which bears adventitious roots and aerial stems
Stems ornamented with silica nodules – sometimes called ‘scouring rushes’
Sporangia are produced in strobili (cones)

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9
Q

Lycophyta

A

Extant members of this group include lycopodium (club moss) and selaginella (spike moss)
Extinct members included the kycophyte trees that dominated the streamy swamp forests of the carboniferous period
Oldest extant group of vascular plants
Dominated major habitats for 40 million years

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10
Q

Improving survival of young sporophytes

A

One of the disadvantages of the fern cycle is – new sporophyte is temporarily dependent on a tiny gametophyte at the start of its life, many new sporophytes perish, would be advantageous if the sporophyte embryo could derive nourishment from the mother sporophyte
For sporophyte embryo to derive nourishment from the mother sporophyte, the female gametophyte (megagametophyte) has to be retained inside the mother sporophyte i.e it develops within the sporangium – for this to work the microspores have to be carried to the megagametophyte in pollen

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