Chapter 22 Flashcards
the name gymnosperm means
naked seed
The female gametophyte is produced inside an
ovule
the ovule contains a fleshy fruit called the
nucellus
The nucellus itself is enclosed within
one or more outer layers of tissue
the outer layers of tissue of the nucellus constitute an
integument that becomes a seed coat after the fertilization and development of an embryo takes place
four living phyla of gymnosperms
- Phylum Pinophyta (conifers)
- Phylum Ginkgophyta (ginkgo)
- Phylum Cycadophyta (cycads)
- Phylum Gnetophyta (Gnetophytes)
Phylum Pinophyta (conifers)
These members bear unique strobili (pine cones) and have leaves that are needle like and arranges in clusters of up to five leaves each. there are about 600 species of pines, spruces, firs, hemlocks, cedars, redwoods and other coniferous woody plants living today
Phylum Ginkgophyta (gingko)
Notched, broad, fan shaped leaves with veins that fork evenly are distinct among ginkgos. The mature seeds resemble small plums and are enclosed in a fleshy covering. Only one species, Ginkgo biloba, exists within this phylum
Phylum Cycadophyta (Cycads)
These slow growing plants have the appearance of a cross between a tree fern and a palm but are not related directly to either group. The strobili of cycads are located in the center of the plant.
Phylum Gnetophyta (gnetophytes)
A unique characteristic of gnetophytes is the presence of vessels and tracheids in the xylem. Many members superficially resemble flowering plants, although they still produce strobilli
Fascicle
cluster of needle like leaves.
regardless of the number of leaves, each fascicle
forms a loose, cylindrical rod
the fascicles are
short shoots with restricted growth
Just beneath the epidermis is the
Hypodermis
the hypodermis consists of
one to several thick walled cells
The epidermis itself is coated with a
thick cuticle
The stomata, instead of being at the surface,
are recessed in small cavities
_____ ______ develop in the mesophyll
resin canals
Resin canals consist of
Tubes lined with special cells that secrete resin
Resin
aromatic and antiseptic and prevents the development of fungi. also deters insect attacks
Abcise
fall off
conifer wood, because of the absence of thick walled cells, Is said to be
soft
broadleaf tree wood is described as
hard
Annual rings are
used to count the age of a tree, look for environmental stressors
Pollen cones
Male strobilli, consist of papery or membranous scales, called microsporophylls, arranged in a spiral or in whorls around an axis. they are usually produced in the spring
Microsporangia develop
in pairs toward the bases of the scales
each of the microsporocytes in the microsporangia
undergo meiosis, producing four haploid microspores
the microspores develop into
pollen grains, each grain consists of four cells and a pair of external egg sacs
Megaspores are produced in the
megasporangia
Megasporangia are located within
ovules at the bases of the seed cone scales, called megasporophylls
the seed cones (female strobili)
are much larger than the pollen cones
The ovules occur in
pairs at the base of each scale of the immature seed cones and are larger and more complex than the microsporangia of pollen cones,
each ovule has within it a
megasporangium containing the nucellus and a single megasporocyte. These are surrounded by an intugement layer
A single megasporocyte within the megasporangium of each ovule
undergoes meiosis, producing a row of four relatively large megaspores
three of the megaspores ________- the remaining one slowly develops into a _____ _______
degenerate, female gametophyte
Pollen grain
immature male gametophyte
Pollen grain produces a ______ ____ that slowly grows and digests its way through the nucellus to the area where the archegonia develop
Pollen tube
While the pollen tube is growing, two of the original four cells in the pollen grain enter it. one of these, called the _______ ____ divides and forms two more cells.
Generative cell
the generative cell divides and forms 2 more cells called the
sterile cell and spermatogenous cell
the spermatogenous cell divides again, forming two
male gametes, or sperms
Ginkgo is _________, with male and female reproductive parts on separate trees
dioecious
