BOT 201 Lycophyta - Lycopodium   Lab    

The Lycophyta constitutes a relatively large group of organisms compared to the Psilophytina and Sphenophytina. However, there are only 6-12 genera and approximately 1000 species. Tree-like lycopods existed during the course of evolution but extant species are small and herbaceous. They are either terrestrial or epiphytic and some species can exhibit both growth forms. Lycopods are most abundant in the tropics, however, some small robust species can be found in temperate forests and even the arctic-alpine zone. They do not usually form dominant components of major ecosystems but may be locally abundant. Lycopodium cernuum (wawae iole - rat's foot) appears to play a role in soil stabilization becuase it grows into disturbed areas where little else grows.

Species of Lycopodium and Selaginella have Microphylls. Microphylls are leaves with only one vascular bundle that is connected to the stele of the stem. They may be Isophyllous (same leaf) or Anisophyllous (not the same leaf). Leaves associated with sporangia (Sporophylls) can differ from vegetative leaves. Sporophylls may be grouped into Strobili (cones) or distributed in sectors along the main stem. Branching is Dichotomous. This can be Isotomous (equal branches) or Anisotomous.   Anisotomus branching occurs when  there is unequal elongation of stems following dichotomous branching. This can result in stems which appear to have one central axis (Monopodial). However, true monopodial branching is a due to lateral branching. Consequently, the term Pseudomonopodial  is applied to Anisotomous. branching which resembles monopodial branching.

Most species have an underground Rhizome which produces aerial branches and roots. A few species have Stolons which are horizontal aerial stems. These produce upright stems and roots. Roots branch dichotomously.

Lycopodium is Homosporous but Selaginella is Heterosporous. We will study Lycopodium in this lab and return to study Selaginella later. Heterosporous forms produce Microspores and Megaspores. These are housed in Microsporangia and Megasporangia. These are produced by microsporophylls and megasporophylls. Heterosporous taxa usually have their sporophylls assembled into cones.

We will concentrate on the most complex species (Lycopodium cernuum (wawae iole - rat's foot) which is found in Hawaii.

This species has a Stolon, Aerial Branches and Adventitious Roots.

External Morphology

What is an Adventitious root?

What is a Stolon?

What type(s) of branching is displayed by this plant?

Can the term Pseudomonopopdial be applied to this species?

Locate the Sporophylls. What is noteworthy about these?

Is this plant Isophyllous or Anisophyllous?

Internal Anatomy

Examine fresh sections of stems, roots and leaves prepared by your dauntless lab instructors (That must include me!!!).

Stain with Phloroglucinol & Toluidine Blue.

Note the general organization of tissues in various stems. It might be useful to make  outline drawings of these.

Is an Endodermis present?

What type(s) of Stele do you see?

Can you locate Leaf Traces in the cortex?

How does the Root anatomy resemble that of the shoot(s).

Compare Sporophylls with Vegetative Leaves from an external and internal perspective.

Is there evidence of structural and functional specialization?

Observe cross  sections of Vegetative Leaves and Sporophylls.

Note Key features of the various tissues.

Is there evidence of Tissue Specialization?

What are the advantages of Cones? I can think of one that involves climate.

Can you think of others?

Tease open some Sporangia and examine spores with your compound microscopes.

What is the color of the spores?

Observe Demo of spores Stained with Sudan.

What type of storage product is present in  the spores?

Observe slides of Vegetative and Reproductive structures & compare these to the plant materials that we examined above.

Selaginella is usually bilaterally flattened and has small dorsal leaves and large ventral leaves. Some species are erect, however. They always have Cones and are Heterosporous. They branch dichotomously and are usually Anisotomous.

Roots originate from the stems and are usually found at branch points. Roots also branch dichotomously.

We will study a species (Selaginella arbuscula) which grows along the Manoa Cliffs trail. It is usually found in dark wet areas and is not extremely abundant so don't pick specimens unless you really need one.

External Morphology

What type(s) of branching is displayed by this plant?

Can the term Pseudomonopopdial be applied to this species?

Locate the Sporophylls. What is noteworthy about these?

Is this plant Isophyllous or Anisophyllous?

Locate an Adventitious root?

Internal Anatomy

Examine fresh sections of stems, roots and leaves prepared by your peerless  lab instructors (That must include me!!!).

Stain with Phloroglucinol & Toluidine Blue.

Note the general organization of tissues in various stems. It might be useful to make  outline drawings of these.

Is an Endodermis present? What is unusual about it?

What type(s) of Stele do you see?

Can you locate Leaf Traces in the cortex?

How does the Root anatomy resemble that of the shoot(s).

Compare Sporophylls with Vegetative Leaves from an external and internal perspective.

Is there evidence of structural and functional specialization?

Observe cross  sections of Vegetative Leaves and Sporophylls.

Note Key features of the various tissues.

Is there evidence of Tissue Specialization?

What are the advantages of Cones? I can think of one that involves climate.

Can you think of others?

Tease open some Sporangia and examine spores with your dissecting microscopes.

Do you detect two spore types? Yes I do? Describe the differences you observe.

Examine the spores at low power with your compound microscopes.

These plants  are Heterosporous.

What are the benefits of heterospory?

Observe slides of Vegetative and Reproductive structures & compare these to the plant materials that we examined above.

Examine Slides which contain cross-sections of Stems, Leaves & Roots

Examine a Demos of a cleared whole Cone (Strobilus).

Locate the Megasporangia & Microsporangia

Follow the development of Megaspores by scanning sporangia from the top to the bottom of the Cone