Lab 4 (plants) Flashcards
why do seasonal allergies exist
Seasonal allergies can result from the pollen produced by male trees, weeds, and grasses. Airborne pollen can cause allergy symptoms such as sneezing, nasal congestion, and irritated, watery eyes. This is because the immune system mounts an immune response to the harmless pollen. Allergy treatment involves inhibiting various aspects of the immune systems when it encounters pollen.
how does the pollen tube influence the success of seed plants
The evolution of a pollen tube, a tubular structure that transports sperm to the ovule, the structure containing female gametes, eliminates the need for water in the transfer of sperm in dry terrestrial environments
how does evolving away from spores let seed plants be successful
Simpler plants use spores, haploid cells that require moisture to give rise to a gametophyte, a haploid multicellular organism that develops sex organs to produce gametes. Gametes are haploid cells that fuse with other haploid cells during fertilization in organisms that reproduce sexually. In contrast to these plants that use spores, seed plants have evolved to produce seeds, protective structures that contain a diploid embryo. The structure of seeds prevents desiccation, reducing reliance on water in dry terrestrial environments. Seeds can rest dormant till conditions are suitable for their continued growth.
how does the endosperm lead to seed plant success
Within the seed, the embryo is surrounded by endosperm, tissues that serves as a source of nutrients that fuels initial growth of the sporophyte, the diploid multicellular stage of a plant that emerges from the plant embryo.
what kind of sporophytes do seed plants have
Seed plants are heterosporous, meaning that the sporophyte produces both female and male spores. The larger female spores are called megaspores, and the smaller male spores are called microspores.
How are seed plants divided
Seed plants are traditionally divided into Angiosperms and Gymnosperms. Angiosperms are flowering plants whose seeds are enclosed within a reproductive structure called the fruit of angiosperms. Gymnosperms are nonflowering plants whose seeds are not protected.
what is the ovule
The female reproductive structure of a seed plant is the ovule. After fertilization the ovule develops into a seed that contains the female reproductive cells and consists of three parts:
what are the three parts of seeds
the integument layer, nucellus, and megagametophyte / embryo
what is the micropyle
The micropyle, a narrow canal in the integument, provides an open pathway for the microspores to enter the internal megasporangium and magaspores.
what is the male reproductive structure of seed plants
The male reproductive structures of seed plants are called microsporangia. Microsporangia produce microsporocytes, also called pollen mother cells, diploid microspore mother cells that undergo meiosis to produce four microspores. Because there are hundreds or thousands of microsporocyte cells within each microsporangium, many thousands of microspores are produced.
what is pollen
Within the cytoplasm of each microspore, a microscopic, multicellular, male microgametophyte develops by mitosis. This entire structure is what is commonly called a pollen grain. The pollen tube, the tube that transports two sperm cells of the microgametophyte to the egg cell of the megagametophyte in the ovule, is a unicellular outgrowth of the inner wall of the pollen grain. Pollen is the powdery substance that contains pollen grains.
what are cones
Gymnosperm means naked seed. Conifers, such as redwoods, giant sequoias, and bristlecone pine trees, are the largest and most important group of gymnosperms. Conifers have two types of organs that contain reproductive structures: male cones, which produce pollen, and female cones, which produce seeds.
where are male cones typically found
The male cones are typically found in clusters at the base of lower side branches, although in some species they can be found on higher branches as well.
what are Microsporophylls
Microsporophylls, modified leaves also called scales, extend out from a central axis and bear one or more microsporangia. Inside each Microsporangium, microsporocytes undergo meiosis produce four haploid microspores that develop into pollen grains.
what does mitosis of the microspore produce
Mitosis of the microspore produces the generative cell, which gives rise to the sperm, and the tube cell, which grows the pollen tube.
what does the pollen grain also consist of in conifers
In conifers, pollen grains also consist of an outer wall, called the exine, an inner wall, called the intine, and a pair of air sacs that make the pollen grains buoyant in the wind.
where do female cones typically form
Female cones typically form higher up in the tree
what are Megasporophyll
the modified leaves or scales of female cones are called megasporophylls. Each scale has two ovules where megaspores can develop.
what does the megasporocute produce
The megasporangium, the middle layer of the ovule, contains a megasporocyte that undergoes meiosis to produced four megaspores. Each ovule also has a micropyle, a small canal in the outer envelope for sperm to enter.
what is pollination
Pollination is the transfer of the whole male gametophyte to the female portion of the plant. In pine trees, wind carries the pollen. Pollination occurs when a pollen grain get lodged between the axis of the female cone and a scale. Fertilization is when the male and female gametes fuse and occurs later.
how does fertilization occur
To accomplish fertilization the tube cell forms the pollen tube. The generative cell travels through the pollen tube, through the micropyle, and enters the female gametophyte. The introduction of the pollen tube stimulates production of the four female megaspres and the development of the female megagametophyte, one of the cells of which functions as an egg. The male gametophyte containing the generative cell splits into two sperm nuclei. One fuses with the egg to produce a diploid zygote in the ovule, while the other deteriorates.
what happens to the zygote after fertilization in gymnosperms
Cells in the zygote divide by mitosis to form the embryo, which is protected by the seed coat. When the embryo is mature, the seed separates from the female cone and is carried to a new location by the wind. The seed germinates and grows to yield a new pine tree.
where do Angiosperm seeds develop
Angiosperm seeds develop and are enclosed within a portion of the parent plant’s flower called the carpel (the pea pod). An angiosperm’s seed is encased in an ovary, containing one or more ovules. The carpel is also composed of the style and stigma
what are Pistils
Pistils are either an individual carpel or several fused carpels
what are Petals and Pedicles
Petals are modified leaves that surround the reproductive structures of the flower and the pedicel is the stem that connects a flower to a group of flowers.
where do female and male gametophytes develop in angiosperms
In Angiosperms, the female and male gametophytes develop in separate structures, though usually in the same flower.
The female gametophyte, the embryo sac, develops in the ovule.
The male gametophyte, the pollen grains, develop in the anthers, a part of the stamen that contains microsporangia.
what is the stamen
The stamen is the anther plus a thin stalk called a filament.
how does fertilization occur in Angiosperms
Angiosperms undergo double fertilization where the female gametophyte joins two male gametophyte. The pollen grain contains 2 sperm nuclei (2n formed from a generative nucleus that splits) and one tube nucleus (n).
The tube nucleus forms a pollen tube that grows through the stigma and the style and into the ovary via the micropyle.
Upon arrival at the ovary, one sperm nucleus fertilizes the egg to make the zygote. The other fuses with two polar nuclei of the egg forming the 3n endosperm.
what are the three parts of a seed
A seed is mature ovule that has three parts:
- a protective coat
- An Endosperm
- An embryo
what do the radicle, cotyledon, and hypocotyl develop into
The radicle develops into the root
The cotyledon develops into the first leaf or leaves
The hypocotyl develops into the stem above the radicle and below the cotyledon
what are Monocots
Monocots are only herbaceous (no wood), have floral organs in multiple of threes, parallel veins in leaves, bundles of vascular tissue scattered throughout the stem, and have only one cotyledon
What are Dicots
Dicots can be woody or herbaceous. Have floral organs in multiples of four or five, net-like veins in leaves, vascular tissue in the stem forms rings, and have two cotyledons.
what happens to the flower after fertilization
After fertilization the petals drop, the ovule develops into a seed, and the ovary becomes a fruit. The fruit develops until the seeds have matured.
what are stone cells
Some fruit like pears have a gritty texture due to the pesence of stone cells in the fruit. Stone cells are a kind of sclerenchyma, a structural tissue that provides support to plants. They influence the overall firmness and weight of the mature fruit. They have a high density of lignin of cellulose and appear dark in slides.
what are Bryophytes
- mosses
- Non vascular
Gametophytes grow Archegonia which produce eggs, or Antheridia which produce sperm. Sporophyte grows out of Archegonium. Seta are stalks which have capsule which release spores from the Peristome.
what are Monilophytes
- ferns and horsetails
- Gametophyte grows Antheridium and Archegonium, Sporophyte grows on Gametophyte. Sorus have multiple Sporangium which release spores from underside of frond.
describe the basic conifer life cycle
Pollen Cones have microsporangium, Ovulate cones have ovules. Pollen reaches other cone. Megasporocyte produces 1 surviving megaspore. Pollen tube delivers sperm nucleus. Fertilization leads to embryo. Sporophyte dominant.
describe the basic angiosperm lifecycle
Anthers have microsporangium which produce microspores with a generative cell and tube cell. Go into sigma, pollen tube delivers sperm to ovule with megaspore. Leads to double fertilization and development of a seed.
what features are ancestral vs derived in flowers
- radial symmetry is ancestral, bilateral is derived
- Fusion of parts derived. Flowers with free parts are ancestral (probably).
where do plants come from
Remember this group from our last in-person lab? This supergroup contains red algae,
green algae, and land plants. The closest living relatives of land plants are the green
algal group called charophytes.
what are Charophytes
This aquatic group of algae is thought to contain the closest relative to land plants. Some
members of this group retain the female gamete (egg) on the parent. After fertilization,
the zygote is also retained. Cells from the haploid parent grow around, protect and
perhaps, nourish the large unicellular zygote
what traits separate plants and algae
Four derived traits separate the land plants from their closest algal relatives:
- Walled spores produced in sporangia
- Production of gametes from gametangia
- Multicellular, dependent embryos
- Growth by apical meristems
what is the first division in plants
The vascular tissues Xylem and Phloem are found in many land plants are perform water and nutrient transportation.
Plants without them are non-vascular including Mosses, liverworts and hornworts
Plants with them are either seedless club mosses, ferns and horsetails. Or seeded Gymnosperms, and angiosperms
what is protonemata
Protonemata is a haploid branched system of filaments rich in chlorophyll that grows from the spores. It produces the gametophyte
what parts of a plant have vascular tissue
Roots, stems, and leaves all have vascular tissues in vascular plants
what are the 4 living gymnosperm phyla
There are four phyla of living gymnosperms: Coniferophyta, Cycadophyta, Ginkgophyta, and Gnetophyta (welwitschia)
what kind of relation do some plants have with bacteria
Mutualism is a form of symbiosis in which both species benefit. For example, certain bacteria which inhabit the roots of plants (especially those in the legume family) form nodules on the roots. These bacteria are capable of fixing nitrogen (a metabolic process) which can be used by the plant.
what type of symbiosis is really common in plants
Most plants require a symbiotic fungus surrounding or penetrating their roots in order to absorb minerals and water effectively. This is known as a mycorrhizal association, also a form of mutualistic symbiosis. The fungal mycelium may simply surround the root and grow into intercellular spaces (ectomycorrhizae), or may actually penetrate the root cell walls (endomycorrhizae). Arbuscular mycorrhizae (Phylum Glomeromycota) are a type of endomycorrhizae that invaginate the cell membranes of plants and form either balloon-like (vesicles) or branched (arbuscules) structures. In either case, the mycelial mat enhances the plant’s ability to absorb water and minerals by increasing the surface area of the root system. In turn, the fungus receives synthesized plant products.
