Non-Vascular Plants: Bryophytes
A. Archegonium and antheridium morphology
Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. In each cycle, a haploid gametophyte, alternates with a diploid sporophyte. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by meiosis, that grow into gametophytes.
Liverworts, mosses and hornworts spend most of their lives as gametophytes. Gametangia (gamete-producing organs), archegonia and antheridia, are produced on the gametophytes.
1. Obtain a slide labeled Mnium (moss) archegonium and antheridium. Observe under the microscope and draw what you see.
2. Obtain a slide labeled Marchantia liverwort archegonia. Observe under the microscope and draw what you see.
VASCULAR PLANTS: Seedless, Lycophytes and Pterophytes
Fern consists of feathery leaves. The plant body is differentiated into roots, stem and leaves. The roots and stem are underground and only the leaves are aerial. Fern plant is classified under Pteridophyta division because they contain feathery leaves. Roots are generally called rhizoid.
Like all other vascular plants, the sporophyte is the dominant phase or generation in the life cycle. The gametophytes of ferns, however, are very different from those of seed plants. They are free-living and resemble liverworts, whereas those of seed plants develop within the spore wall and are dependent on the parent sporophyte for their nutrition.
The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is often referred to as a frond. New leaves typically expand by the unrolling of a tight spiral called a crozier or fiddlehead into fronds. This uncurling of the leaf is termed circinate vernation. Leaves are divided into two types: sporophylls and tropophylls. Sporophylls produce spores; tropophylls do not. Fern spores are borne in sporangia which are usually clustered to form sori.
A fern gametophyte typically consists of:
Thallus: A green, photosynthetic structure that is one cell thick, usually heart or kidney shaped. The prothallus produces gametes by means of:
Antheridia: Small spherical structures that produce flagellate sperm.
Archegonia: A flask-shaped structure that produces a single egg at the bottom, reached by the sperm by swimming down the neck.
Rhizoids: root-like structures (not true roots) that consist of single greatly elongated cells, that absorb water and mineral salts over the whole structure. Rhizoids anchor the prothallus to the soil.
1. Obtain the slide labeled fern archegonia and observe under the microscope. Draw what you see.
1. Observe the fern specimen under the dissecting microscope. Then prep a sample of spores from the sori to view under the light microscope. Draw both images below.
VASCULAR PLANTS: Flowering, Seed-Bearing Vascular Plants (Angiosperms)
B. Monocot Vs. Dicots Flower Morphology (Observation and Drawing)
Review the chart below and become familiar with the difference between monocot and dicot morphology.
Obtain a monocot and dicot leaf slide and examine it under the microscope. Draw what you see below. Label each drawing monocot or dicot.
Obtain a monocot and dicot stem slide and examine it under the microscope. Draw what you see below. Label each drawing monocot or dicot.
PROCEDURE- The Reproductive Structure of Angiosperms. The Flower. (Observation and Drawing)
1. Obtain a lily flower. Using the dissection microscope (if necessary), locate and examine each of the following structures: (note, not all flowers have all these structures).
BRACTS- some flowers (not all) have specialized leaves associated with the flower. These floral leaves are called bracts. Some bracts are showy (the red "petals" of Poinsettia and the white "petals" of dogwood are actually bracts- the true flower parts of these species are actually quite small). (see examples in lab or in your atlas).
SEPALS (plural- calyx). The sepals surround the flower base and are the outermost structures of the flower; they are typically green, although they may be large, showy and colorful. In some cases sepals may be absent.
PETALS (plural- corolla). The petals are internal to the sepals, and may be green, white or highly colored. In addition to color, petals may also have structures producing fragrance or otherwise associated with enticing pollinators. Sugar producing cells called nectaries are often associated with petals.
STAMENS (male reproductive structure) (plural- androecium). The stamens are structures internal to the petals. Each stamen typically consists of a stalk (the filament) and a terminal sporangium (the anther), which when mature contains the pollen grains. The pollen grains are the microgametophyte (multicellular haploid portion of the angiosperm life cycle) and contain 3 cells (discussed below).
PISTIL (the whole female reproductive structure) (plural- gymnasium). The pistil is found in the center of the flower. The pistil is divided into the stigma (the tip where pollen lands), the style (pistil stalk) and the ovary (where ovules are located). Within the ovules is found the megagametophyte. The ovary is the structure that typically develops into the fruit. The pistil may be longitudinally divided into fused locules (e.g. each orange wedge is a locule).
2. Draw the Lily complete flower labeling flower parts.
C. The Male Part of the Flower. Anthers (Male Spores and the Male Gametophyte). (Observation and Drawing)
We will be making microscopic examinations of the reproductive parts of lily flowers. Review the structures of a lily flowers available in lab.
Young lily anther. Examine prepared slide lilium anthers early prophase. Locate the cells that will divide to form the male spores. The male spores will divide mitotically forming the small multicellular male gametophyte (only 3 cells) termed pollen grains. Draw what you see below
Older lily anther. For a more detailed examination of the pollen grain, obtain prepared slides showing a section through an older lily anther (slide labeled lilium anther 1 celled microspore). Locate the numerous maturing pollen grains. Examine at 400x. Draw a cross sectional view of a prepared slide of older lily anther at 400x. Label male gametophyte (pollen grains).
Fresh pollen. Using a cotton swab, lightly touch the anther of a lily. Touch the cotton swab to a drop of water on a microscope slide, add a cover slip and examine it under the microscope. Pollen structure differs between groups of plants and has been used for forensic, anthropology, ecology and evolutionary studies. Draw what you see.
D. The Female Part of the Flower. Ovaries, Ovules, and the Female Gametophyte. (Observation and Drawing)
1. Lillium megaspore. Examine the slide and draw below.
2. Draw a 400x view of prepared slide of lilium ovule mature ombryo.