Labs 1-3 Flashcards
What two means of dispersal have plants evolved?
Plants have evolved two means of dispersal: spores or seeds
How do the seedless plants disperse?
- They disperse as spores
- The seedless plants include the bryophytes (liverworts, hornworts, mosses), the lycophytes (club mosses, quillworts Selagineslla), Psilotum, horsetails, and ferns
What are spores?
Spores are thick-walled single cells that are typically wind dispersed
How do the seed plants disperse?
- they disperse as seeds
- each seed includes an embryonic plant supplied with stored food
- the seeds are dispersed by various means, depending on the design of the seed
What is in a seed?
- each seed includes an embryonic plant supplied with stored food
- the seeds are dispersed by various means, depending on the design of the seed
Gymnosperms
- the naked-seeded plants that include the conifers, ginkgo, cycads, and several others
- “gymnos” =naked
- “sperma” =seed
- the seed is naked because the ovule from which it developed was naked (not enclosed in tissue)
Angiosperms
- the flowering plants
- seed is enclosed because the ovule from which it developed was enclosed within the ovary of the flower’s pistil
- (Greek: angeion = container; the seeds are contained, enclosed within a fruit, although at maturity the fruit may split open to release the seeds)
Ovules
- produced by all seed plants
- develop into seeds after fertilization
- the structure contained within the ovary that gives rise to the female gametophyte and, when fertilized and mature, a seed
- embedded within the tissue of each ovule is an egg cell; the egg cell is located near a tiny opening in the ovule called the micropyle (Greek: mikros = small; pyle = gate)
- Pine: ovules on the scales of young female cone
- Flower: ovules within the ovary
What do all seed plants produce?
Ovules and pollen
Pollen
- Pine: produced by separate male cones
- Flower: produced by anthers
- pollen grains contain sperm cells, after a sperm fertilizes the egg cel in an ovule, the ovule matures into a seed
- (Latin: pollen= fine flour)
What are the parts of a seed?
- Seed coat
- embryo
- nutritive tissue
Seed coat
- a protective covering that developed from the outer layers of the ovule and is thus material from the mother plant
- the seed coat may have structural modifications to assist in seed dispersal; for example, many pines produce “winged” seeds, the wing being a dry extension of the seed coat that aids in gliding through the air
Embryo
- the offspring plant that developed from the fertilized egg
- attached to the embryo are one or more fleshy, nutrient-rich structures called cotyledons
Cotyledons
- fleshy, nutrient-rich structures
- attached to the embryo are one or more of these
- gymnosperms tend to have several cotyledons per embryo
What two groups are angiosperms divided into?
- Monocotyledons or monocots (one cotyledon per embryo)
- and dicotyledons or dicots (two cotyledons per embryo)
Monocotyledons (monocots)
One cotyledon per embryo
Dicotyledons (dicots)
Two cotyledons per embryo
nutritive tissue
- Stored food
- provides the germinating seedling with energy for a brief period
Endosperm
The nutritive tissue in angiosperm seed
Hilum
- Belly button
- The point at which the seed was attached to the inside of the ovary
Micropyle
the small opening or “gate” through which the pollen tub entered the ovule in order to deliver the sperm to the egg
Scarification
Rubbing seeds between sandpaper or soaking them in acid
Stratification
Placing seed between moist layer of sand or paper towels in a refrigerator
Imbibition
a passive process that swells the seed
Cellular respiration
An enzymatic process that breaks sown materials
Dormancy
defined as the failure to germinate even under optimum condition of moisture, temperature and aeration
P(r)
- does not germinate
- absorbs red light and changes to P(fr)
P(fr)
- ready to germinate when in this form
- when absorbing far red light turns back to P(r)
Gibberellic Acid (GA)
Can be used as a substation for light in germination of seeds
