Exercise 28
1. Rhizoids serve to anchor the plant to the substrate and absorb water and minerals. Also, the rhizoid attaches the gametophyte to the substratum and facilitates the absorption of minerals and water. Anchorage + absorption. Rhizoids are nonphotosynthetic and anchor the protonema to the substratum.
2. Each pore leads into an air chamber containing columns of photosynthetic cells and facilitates in gas exchange. Unlike the stomata of vascular plants which close in dry weather, the air pores of liverworts remain open all the time.
3. Antheridia need to disperse sperm and are upright with pores on top of the antheridial disk; archegonia are protected under the surface of the archegonial disk.
4.
a. The sporophyte is formed and is attached to the mother gametophyte by a foot through which the nutrients are passed between the sporophyte and the gametophyte. Anchors sporophyte to archegoniophore.
Nutrient transfer from gametophyte to sporophyte
b. Spores are haploid.
c. The spores are helped on their journey by four strap-like structures called elaters that catch the wind. The elaters coil and uncoil in response to changes in humidity. When the air is dry they extend outward and create wind resistance so that the spores float. When the air is humid the elaters coil around the spore so that buoyancy decreases and the spore drops--with luck onto moist soil where it can germinate.
5.
a. The leaves are delicate, thin and flat and only one cell thick except at the midrib.A few mosses such as Polytrichum have extra rows of cells, making the leaves harder, drought-resistant and more difficult for chemicals to penetrate
1-2 Cells thick
b. There is a slightly thickened midrib that runs lengthwise down the middle.
c. Pores are visible on the leaf surface.
d. The moss gametophyte is radially symmetrical, and is the most conspicuous phase of the moss life-cycle. The gametophytic thallus of the liverwort grows as a large, flat, photosynthetic structure on the surface of the ground
6. …
7. Each archegonium holds one egg in the venter and the sperm enter through the channel in the narrower, tubular section/neck. On the side of the venter opposite the neck is the foot which anchors the archegonium to the gametophyte
8. Sperm are haploid.
9. The sporophyte is more prominent In liverworts. With every Phylum, the sporophyte gets larger and more prominent.
10. The seta of the sporophyte grows above the mat of the gametophyte for a couple of reasons. First, the sporophyte is dependent on the gametophyte for water and nutrients. The seta acts as a tube through which these nutrients are supplied to the sporophyte, ensuring its survival. Also, the elongation of the seta pushes the sporangium upward. When the sporangium releases the spores, the elevation allows the spores to be caught by the wind and spread so that new plants can grow.
11.
a. Spores are produced by meiosis. The sporophyte grows on the gametophyte and eventually produces spores by meiosis.
b. The sporophyte capsule is diploid (2n).
12. The moss protonema is created when the spore of a moss germinates and develops a green filamentous pro-embryo, the protonema. The protonema later produces buds that grow into leafy gametophytes. These gametophytes have stemlike and leaflike structures that are photosynthetic and are able to supply the plant with nutrients and water. This allows the plant to survive in places where light is limited because, once light is present, the gametophyte is able to efficiently and quickly go through photosynthesis.

Exercise 29
1. …
2.
a. The parts of a Fern’s life cycle that are haploid are: the spores, the gametophyte, the rhizoids, the antheridium, the archegonium and its egg and the sperm, all before fertilization occurs.
b. The diploid parts are: after fertilization occurs - the zygote and the embryo, the adult sporophyte, the sporangium, the frond, and the mature sporangium.
3.
a. Fronds have a different amount of veins depending on their size. Based on the plants available in the lab, the small sized fronds have 10-20 veins, the medium sized fronds have about 40-50 veins, and the large sized fronds have 50+ veins.
b. The veins of vascular tissues are comprised of both xylem and phloem.
c. The stalk is the portion of the frond that is below the leaflets. It serves to support the leaflets and supply them with water and nutrients. The blade of the fern is called the lamina. It is responsible for photosynthesis and for carrying/supporting the leaflets. The pinnae is a part of the frond and stores the spores.
4. There are spores in the sporangium. The particular slide I was looking at had two sporangium with spores inside.
5.
a. …
b. In bryophytes, sporophytes make spores in the sporangium. When it is ready, the sporangium, which sits on top of the gametophyte, opens or breaks and releases the spores which are spread by the wind. In ferns, the sporophytes also make spores and then these spores are released by the sori when the time is right. Then, the spores are dispersed by the wind, just like in bryophytes. The difference is that a fern sporophytes (2n) produce haploid (1n) spores through meiosis. Also, the sori is located below fern fronds(leaves) and not on top of the plant like in mosses.

6.
a. The prothallium is haploid.
b. The prothallium is gametophyte.
7.
a. The advantage to having the archegonia and antheridia under the prothallium is as follows: when the antheridium jacket cap cell disintegrates under falling rain, its’ sperm are released and able to find open archegonium. The rain would also cause the archegonium jacket cap to disintegrate, allowing the sperm to swim right in.
b. Having the sperm and egg produced at different times limits the chances of inbreeding and ensures the variability in the offspring plants.
8. …
9.
a. The branching pattern of Psilotum is called bifurcation. This means the division into two branches. This type of branching is also called pseudodichotomous.
b. There are no roots on the plant.
c. There are no leaves on the plant. Instead, it has enations which are epidermal flaps along the length of the shoot.
d. The sporangia form on the stems of the plant and are called synangia.
e. Photosynthesis occurs in the aerial stems of the plant.
10.
a. The leaves of Equisetum are arranged in true whorls and the leaves of each whorl are fused together to form a cylindrical sheath around each node. The leaves also alternate with branches at each node on the stem.
b. The gametophytes, the aerial stems are photosynthetic. Photosynthesis is carried out by the stems and branches, if they are present.
c. The dominant part of the Equisetum life cycle is the sporophyte.
11. The elaters aid the dispersal of spores by coiling and uncoiling depending on the weather. When it is moist, the elaters coil and the spores stick together, preventing dispersal in unfavorable conditions. When the weather is dry, the elaters uncoil and allow the spores to be caught in the wind and spread.
12.
a. A rhizome is the horizontal underground stem of a plant. It is involved in asexual reproduction because it is capable of producing the shoot and root systems of an entirely new plant. When the rhizome grows from the original plant it is able to invade or spread to nearby soil. Once this happens, it is able to create new flowering stalks from which new plants can grow. This process creates a patch of plants all growing in close proximity due to their sharing the same root system. Also, if the rhizome of a plant is cut and the roots are not eliminated, the root itself does not die. It can create a new plant altogether.
b. A rhizome is a modified stem/root that supplies plants with food, water, and other valuable nutrients. A rhizoid is simply a filament that anchors a plant to the ground. It does not provide the plant with anything aside from stability.
c. The rhizome does have leaves. They appear as small and scaly or filmy.
d. The leaves are small, scaly or filmy. These leaves contain axillary buds that can grow to produce branches or the above ground leaves of the plant.
e. The nodes that are enclosed in the leaves of the rhizome grow upward/above ground to produce the leaves or branches of the plant.
f. Yes. Each leaf has one unbranched midvain.
g. The word evergreen refers to a plant that retains green leaves throughout the entire year.
13.
a. Each sporophyll of Lycopodium has one sporangium.
b. …
c. …
d. The sporophyte is the dominant part of the Lycopodium life cycle.
14.
a. Selaginella is heterosporous so it has spores with two distinct sizes, microspores and megaspores.
b. This condition, a plant having differently sized spores, is called heterosporous.