Lab 10: The Land Plants - An Evolutionary Overview Glossary
Alternation of Generations (Sporic Meiosis) :
The life cycle type of all land plants and some algae, characterized by alternation between multicellular haploid (gametophyte) and diploid (sporophyte) generations.

Isomorphic Alternation of Generations: Gametophyte and Sporophyte generations are identical in form. Characteristic of some algae (such as Ulva) with sporic meiosis.
Heteromorphic Alternation of Generations: Gametophyte and sporophyte generations are visibly different. Characteristic of all land plants. 

Diagram of Sporic Meiosis Life Cycle Diagrams: Ulva, Liverwort, Moss, Selaginella, Fern, Equisetum, Conifer, Flowering Plant. 

 
Antheridium:
The male, sperm-producing gametangium on the gametophytes of liverworts, mosses, hornworts, lycophytes, ferns, and horsetails, and some algae. True antheridia, with differentiated layers of sterile tissue surrounding the spermatogenous cells, first appeared in the Charales.
 
 
Anthocerotophyta (hornworts):
An early-evolved lineage of land plants, closely allied to liverworts and mosses and commonly known as hornworts. Stomata first appeared in this lineage.

| Picture | Anthocerotophyta section of Lab 10 | Cladogram |

Anthophyta (flowering plants):
The lineage of seed plants that includes all flowering plants, characterized in part by highly reduced gametophytic generations dependant on the sporophyte, the presence of vessel elements in the xylem, sieve tube elements with companion cells in the phloem, the enclosure of ovules within a protective structure called the ovary, and the production of elaborate strobili called flowers, which function to attract Traditionally divided into two classes, the monocotyledons and the dicotyledons, though it is now known that the dicots comprise a paraphyletic grouping.

| Anthophyta Section of Lab 10 | Lab 12 - Reproduction in Seed Plants | Lab 13 - Flowers and Pollination|

Archegonium:
The female, egg-producing reproductive structure on the gametophytes of non-flowering land plants. The archegonium is comprised of an oogonium surrounded by protective layers of thick-walled, pigmented cells, and may be differentiated into an elongated neck reagion and an expanded basal region, called the venter, which contains the oogonium and egg.
 
Bryophyta (mosses):
The lineage of non-vascular land plants also known as mosses. "Bryophyte" is also a term sometimes used to refer collectively to the three lineages of non-vascular land plants, the liverworts, hornworts, and mosses.

| Bryophyta section of Lab 10 | Moss life cycle - Lab 11| Cladogram |

Carboniferous Forest:
During the Carboniferous period, from 360 to 286 mya, very lush, swampy forests dominated the landscape in low-lying areas, where minor changes in sea level alternately exposed land supporting forest then inundated and buried the vegetation. The forests were dominated by arborescent lycophytes, sphenophytes, and others, and the forest floor supported ferns and seed ferns. The buried vegetation was compressed and changed through time to form extensive coal deposits, in which plants are common fossils.

| Lycophyta section of Lab 10 |

Charales:
A lineage of freshwater algae that is closely related to land plants. Charales marks the appearance of several characters thought to be important in the evolution of land plants, including plasmodesmata, apical growth, retention of the egg cell within sterile parental tissue prior to fertilization, enclosure of gamete-producing structures within sheaths of protective sterile tissue, the presence of flavinoid pigments, and the retention and nourishment of the developing zygote for a time within the parent gametophyte. Charales are characterized by a zygotic meiosis life cycle.
| Picture| Cladogram |
Charophytes:
A collective term for the algal lineages most closely related to land plants, including the Coleochaetales, Charales, and Zygnematales, and united in a lineage with the land plants by the synapomorphies at node 4 on the tree.
Coleochaete:
A genus of small, multicellular, freshwater algae, thought to be the sister-group to the land plants. Coleochaete shares two important characters with land plants: the retention of the zygote within the parent until meiosis and sporogenesis are completed, and the nourishment of the developing zygote by the parent tissues until sporogenesis is completed. Coleochaete has a zygotic meiosis life cycle.
| Picture| Cladogram |
Conifer:
The largest monophyletic group of non-flowering seed plants. Conifers are generally evergreen trees with needle-like leaves, and bear their fertile parts (microsporangia and megasporangia) in unisexual strobili, or cones. The ovules are born naked on the upper surface of the scales of the female cone, so conifers are traditionally included in the artificial grouping "gymnosperms."
| "Gymnosperm" section of Lab 10 | Conifer Section of Lab 10 | Lab 13 - Reproduction in Seed Plants |
Cuticle:
A thin, waxy, protective layer covering the surface of the stems and leaves of land plants. A necessary adaptation to life on land, the cuticle is composed of a complex mixture of fatty acid derivatives with waterproofing qualities that protect the plant from excessive water loss and dessication in a dry atmosphere. A cuticle first appeared in the liverworts.
| Picture |
Cycadophyta:
A lineage of non-flowering seed plants. Cycads are palm-like in habit, with male and female reproductive structures born on separate plants and usually arranged in strobili. Cycads retain the primitive character of flagellate motile sperm cells, which are contained within the pollen grain.
| Cycad section of Lab 10 |
Dichotomous:
Branching into two equal parts, as in the stems of Psilotum.
 
Dicotyledon:
A flowering plant in which the embryo characteristically has two cotyledons (embryonic leaves), which often serve as the first photosynthetic structures for the seedling after germination. Traditionally, dicotyledons were one of the two classes of flowering plants (Anthophyta), but are now known to be paraphyletic. See monocotyledon.
| Anthophyta section of Lab 10 | Lab 13 - Reproduction in Seed Plants | Lab 14 - Plants and the Environment |

Diploid:

Egg:
A large, non-flagellate female gamete.
Embryo:
A multicellular diploid structure resulting from mitosis of the zygote. A very young sporophyte.
Epidermis:
The living surface tissue of plant organs.
Fertilization:
The process of fusion of two compatible gametes to form a zygote.
Frond:
A large compound leaf. This term is usually used to describe the leaves of palms and ferns. (image)
Gametangium:
An organ of the gametophyte in which gametes develop. See antheridium, oogonium, archegonium.
| Lab 11 - Reproduction in Non-Seed Plants | Lab 12 - Reproduction in Seed Plants |
Gamete:
A specialized haploid cell whose nucleus and often cytoplasm unite with that of another gamete (from the opposite sex or mating type) in the process of fertilization to form a diploid zygote.
Gametophyte:
The multicellular haploid phase in the lifecycle of organisms with zygotic or sporic meiosis life cycles. Gametophytes produce gametes via mitosis in structures called gametangia. Unisexual male and female gametophytes may be referred to as microgametophytes and megagametophytes, respectively. See also sporophyte. The gametophyte is the dominant stage in the life cycles of liverworts, mosses, and hornworts.
Ginkgophyta:
A gymnosperm lineage represented by a single extant species, Ginkgo biloba, commonly cultivated dioecious trees with easily-recognized leaves.
|Ginkgophyta section of Lab 10|
Gnetophyta:
The gymnosperm lineage thought to be most closely related to flowering plants. Gnetophyta contains three extant genera: Gnetum, Ephedra, and Welwitschia.
|Gnetophyta section of Lab 10|
Gymnosperm:
Term used to refer collectively to the non-flowering seed plants, in which the ovules are borne exposed, such as on the surface of sporophylls, rather than being enclosed within an ovary. (G. gymno, naked, bare + sperma, seed)
Haploid:
A cell with only one set of chromosomes, or an individual with one set of chromosomes per cell. The haploid state is indicated by "n" to distinguish it from the diploid state, "2n."
Hepaticophyta:
A gymnosperm lineage represented by a single extant species, Ginkgo biloba, commonly cultivated dioecious trees with easily-recognized leaves.
Heterosporous:
Producing two morphologically distinct types of sporangia (megasporangia and microsporangia) that produce two distinct types of spores (megaspores and microspores), which develop into separate male and female gametophytes (i.e., unisexual gametophytes). Heterosporous plants covered in Bio 240 Lab include Selaginella, heterosporous ferns, "gymnosperms," and flowering plants.
Homosporous:
Producing a single type of sporangium, which in turn produces a single type of spore. Gametophytes of homosporous plants may be bisexual, with both male and female gametangia, as in ferns, or unisexual, as in most mosses. Homosporous plants covered in Bio 240 Lab include liverworts, mosses, hornworts, Lycopodium, most of Pterophyta, and horsetails.
Integument:
The outer tissue layers of an ovule, covering the megasporangium. The earliest-evolved plants in which an integument (or ovule, for that matter) can be seen are the "gymnosperms," and a double integument is found in many flowering plants.
|Lab 12 - Reproduction in Seed Plants|
Internode:
The region of a stem between two nodes.
Leaf:
A flattened photosynthetic structure attached to the stem at a node. True leaves also have a vascular supply.
Megasporangium:
In heterosporous plants, a sporangium that produces megaspores. Often larger than the microsporangium, and producing 4 (or sometimes 1, as in seed plants) megaspores.
Megaspore:
In heterosporous plants, a haploid spore produced within a megasporangium of the sporophyte. Upon germination, megaspores produce unisexual female gametophytes (megagametophytes).
 
Microsporangium:
In heterosporous plants, a sporangium that produces microspores.Usually morphologically distinct from the megasporangium. Generally, large numbers of microspores are produced.
Microspore:
In heterosporous plants, a haploid spore produced within a microsporangium of a sporophyte. Upon germination, microspores produce unisexual male gametophytes (microgametophytes).

Monocotyledon:

A flowering plant in which only one embryonic leaf is present. Monocotyledonous plants comprise a monophyletic lineage derived from within the dicots.
|Anthophyta section of Lab 10| Lab 13: Reproduction in Seed Plants| Lab 14: Plants and the Environment|
Node:
The point of attachment of a leaf; also, the point of branch emergence.
Oogonium:
A unicellular gametangium that contains an egg.
Ovary:
A sporophytic structure that encloses the ovules in flowering plants (anthophyta). See also pistil, carpel, style, stigma, ovule, gynoecium.
Ovule:
Seed plants: A megasporangium covered by an integument. A single spore within the megasporangium develops into the megagametophyte, which ultimately produces one or more egg cells. Upon fertilization of the egg, the ovule becomes a seed.
Phloem:
Vascular tissue with a photosynthate (food) conducting function. True phloem consists of living, thin-walled cells, typified by sieve areas in the walls of some of the cells.
Psilophyta:
See Lab 10: Psilophyta
Pterophyta:
See Lab 10: Pterophyta
Rhizoid:
A unicellular or multicellular absorptive and anchoring filament, lacking vascular tissue, found in the gametophytes of mosses, liverworts, and ferns, for example.
Rhizome:
A fleshy, elongate, non-erect stem, often, but not always, subterranean. See ferns.
Root:
An anchoring and absorptive structure with a central vascular supply.
Seed:
A fertilized ovule. A seed consists of an embryonic sporophyte embedded within parent sporophytic tissues and surrounded by one or more integuments, which comprise the seed coat.
Sorus:
A group or cluster of sporangia in ferns.
Sporangium:
Spore-producing structure on a sporophyte. In heterosporous plants, two types of sporangia are produced: megasporangia and microsporangia.
Spore:
Generally, a unicellular haploid phase in the lifecycle of land plants and some algae. In organisms with alternation of generations, spores are produced in the sporangia of the sporophyte via meiosis. Spores act as units of dispersal in the non-seed land plants.
Sporic Meiosis:
See Alternation of Generations
 
Sporophyll:
A modified leaf bearing one or more sporangia, generaly referring to the component structures of a strobilus.
Sporophyte:
The diploid, spore-producing generation in plants with alternation of generations. In liverworts, mosses, and hornworts, the sporophyte is completely dependent on the gametophyte. In Lycophytes, ferns, and horsetails, sporophytes and gametophytes are generally independent and free-living. In the seed plants, the sporophyte is the dominant stage in the life cycle, and the gametophytes are highly reduced and dependent on the sporophyte.
 
Stem:
The primary axis of a plant, to which other organs, such as leaves, are attached. Divided into nodes and internodes.
 
Stomata:
A minute, intercellular fissure in the epidermis of a stem or leaf, flanked by guard cells that regulate the opening and closing of the stomata in response to complex hormonal signals and environmental cues in order to modulate the diffusion of water vapor and other gasses out of and into the plant. Stomata first appear in the sporophytes of hornworts.
Strobilus:
A specialized reproductive structure consisting of a stem with short internodes and sporangium-bearing appendages, generally modified leaves called sporophylls, attached in a spiral pattern.
Thallus:
A vegetative form lacking stems, roots, or leaves, such as the gametophyte of a thalloid liverwort or a fern.
Xeromorphic:
An organism bearing adaptations that allow it to survive arid conditions.
Xylem:
Vascular tissue specialized for the conduction of water. Cells of the xylem are dead at functional maturity, consisting only of primary and secondary cell walls.
Zygote:
A diploid cell formed as a result of fertilization, the fusion of 2 compatible gametes.