Saturday, March 26, 2011

Lab 9 - Angiosperm Reproduction

Angiosperm Reproduction

Forsythia is bisexual (meaning its flowers have both male and female bits) like the majority of the flowers. 

 The female floral parts: the stigmatic surface, the ovary and the style that connect the stigma to the ovary. Collectively they are call a pistil

The male bits of the flower: anthers which contain pollen grains and filaments which hold up the anthers. Together they are called stamens

Phaseolus coccineus or scarlet runner bean. The oval scar is the hilum and it is where the seed was attached to the placenta. The tiny pore above the hilum is the microphyle

One of the two cotyledons will have a plumule (where the stem and leaves develop) and a radicle (where the roots develop).

Tulipa (tulip) flower have almost identical petals and sepals. When we can't distinguish petals from sepals we call them tepals

Examine the stamens and pistil of the flower. The pistil of this flower lacks an style. Instead, the stigma is attached directly to the ovary.

A cross section of the ovary. This ovary has 3 locules and the type of placentation is axile

A way to identify the number of locules in the ovary is to look at the sigma. A 3 lobed stigma suggest this ovary has 3 locules.

Antirrhinum(snapdragon) flowers have bilateral or zygomoprhic symmetry.

A cross section of the ovary reveals 2 ovules and ovules in axile placentation. Axile placentaiton refers to the ovules that are attached to the central placenta.

Narcissus (daffodil) flowers.

The sepals, petals and stamens are fused together at the base to form an hypanthium. The petals, septals and stamens are above the ovary, therefore, this flower is epigynous.

The longitudinal section shows the ovules attached to a central placenta...axil placentation.

Another view of the axile placentation. A cross section can also reveal the number of locules and in this case it's 3.

Prunus (cherry) flowers.

These flowers have cup-shaped hypanthium. Similar to the daffodil flower above, these flowers are also epigynous.

Salix (willow)

Some plants are unisexual and has only the female or male parts in their flowers (ie. dioecious). Willow flowers are unisexual and borne in catkins or clusters of many unisexual flowers.

A sunflower is a composite meaning it is made up of many individual flowers. The yellow 'petals' are actually ray flowers, and the dark centre is comprised of many disk flowers.

Cross section of a composite head. Note the disk flowers in different developing stages.

A disk flower. The sepals have been modified to fine hairs called pappus.

Solanum esculentum (tomato)

Tomato flowers have fused stamens.

The tomato fruit type is a berry. Tomatoes have axile placentation.

Strawberries are not actually fruits (they are accessory fruits). The receptacle of the flower has swollen up into the juicy fruit that we eat and the seeds are the actual dry fruits call achenes

If you were give this flower on the lab final exam, would you be able to label the following? Stigma, style, ovary, pistil, anthers, filaments, stamens, petals, corolla, sepals, calyx
Is this flower hypogynous, perigynous or epigynous?

This Fuchsia flower is epigynous.

Thursday, March 24, 2011

Lab 8 - Conifers

C. Reproduction in the Conifers

Conifers are usually monoecious (bisexual).
Mature seed cone are larger than pollen cones.

- Pollen cone of Pinus (Pine)

The microsporangia is on the abaxial (lower) surface of the microsporophylls.

The pollen grain of pine has air bladders.

- Pollen cone of other conifer species

Many other conifer species actually do not have air bladders, such as the giant sequoia.

Pollen cone of Giant sequoia (Sequoiadendron giganteum).

The pollen cone of the giant sequoia does not have air bladders.

- Prepared slide of Pinus pollen cone longitudinal section

Longitudinal section of the pollen cone.

cross section and longitudinal section of the pollen cone.

- Seed cones of Pinus
The cones are red when it is pollinated.

This green/brown cone is about one year after pollination occurs.
Fertilization will soon occur as the megagametophyte has completed development.

Two years after pollination. 
The seeds are mature.

The ovuliferous scales:
The demo.
The ovules are on the adaxial side of the ovuliferous scale.
There are two ovules on each scale.

- Prepared slice of Pinus seed cone longitudinal and cross-section
An overview of the seed cone.

A closer look at the longitudinal section of the seed cone. (Picture by Midy)

- Prepared slides of Pinus embryo
Nucellus is hapliod.

- Germinating Pinus seed

Different stages of germinating Pinus.

The cotyledons and the young needles are borne singly (spirally arranged), not in fascicles (short shoots) as on mature plant.

Mature Pinus has leaves borne in fascicles.

- Yee Sing

Sunday, March 13, 2011

Lab 7 - Monilophytes II: Psilotaceae, Ophioglossaceae and Leptosporangiate ferns

Note the dichotomous branching pattern (ie. one branch give rise to 2 branches) on this Psilotum

Synangium is the structure formed by the fusion of 3 sporangia. You can still see the 3 thirds of sporangia.

Psilotum has protostele vascular tissue arrangement. 

The ring of blue-staining cell walls is the Casparian strip. These cells have lignin and/or suberin in their cell walls to prevent apoplastic movement of water and nutrient.


The fronds (also known as leaves) of Ophophioglossum sp. are made of 2 parts: a sterile blade and a fertile segment with 2 rows of eusporangia

Cross-section through eusporangia of Botrychium. Note the homosporous spores (spores of the same size).

Rhizome cross-section of Botrychium.


A fern from Pacific Spirit Park. The central 'stem' (in red) that runs throughout the frond is the rachis. Deriving from the rachis are pinna (in blue). And the smaller divisions coming from the pinna are the pinnule (in yellow). The bottom half of the rachis without any pinna attached is the petiole (not shown here). 

Some ferns don't have pinnules in their fronds and instead they end in pinna as in this sword fern. 
Sword fern's name came from its pinna that resemble swords (complete with hilts and blades).

Polypodium vulgare (licorice fern).

The scattered nodes of previous leaf attachments. Some leaves can arise from the bottom side of the stem and twist its way toward the sky.

Pteridium rhizome cross-section (1 of 4). Pteridium is amphiphloic and has dictyostele with 2 rings of vacular bundle. The bundles aboves are part of the outer ring.

(2 of 4) As we move inwards we see the second ring.

(3 of 4) The first half of the inner ring.

(4 of 4) The two halves of the inner ring.

Polypodium rhizome cross-section (1 of 2). Polypodium rhizomes are also amphiphloic with dictyostele but with only a single ring.

(2 of 2) The centre of the rhizome does not have another ring.

Amphiphloic Adiantum rhizome cross-section. (1 of 2)

(2 of 2)

The backsides of sword fern pinna are lined with sori (groups of sporangia).

Sori are mostly found on the underside of the fronds. These are from Cyrtomium falcatum.

Sori may be naked (without indusium).

Some sori are located on the marines of the fronds.

A sporangium under a compound 'scope. Note the thick walled annulus (or the Mohawk), the lip cells (near the opening), and the spores.

This sporangium is intact and has not burst open yet.

Fern gametophyte with archegonia, antheridia and rhizoids.