Week 5

phlya Ginkgophyta, Gnetophyta, Cycadophyta and Coniferophyta
vascular plants with true roots
gymnosperms = “naked seeds”
have seeds that develop on the surfaces of sporophylls instead of in ovaries like
microsporangium produces pollen grains (sperm) and the megasporangium
produces the egg
sporophyte generation is dominant
no water needed for fertilization – pollen travels with the wind
Pine trees
monoecious (separate male and female cones on the same plant)
have needle-shaped leaves that adapt the tree to dry conditions
produce cones – male and female
male cones produce microsporangia (pollen sacs) that produce microspores (4)
which mature into pollen grains (microgametophyte) with wings for wind
female megasporocytes within the ovule undergo meiosis early producing
megaspores (4) of which three degenerate and one is functional – this one
undergoes mitosis to produce the female gametophyte (megagametophyte) = egg
which lies in the archegonium
Fertilization – pollen sticks to female scales to a drop of fluid which evaporates
moving the pollen closer to the megasporangium and then the scales close. Pollen
tube then grows down into female gametophyte and the pollen divides into 2
sperm – one fertilizes the egg to produce a zygote and the other disintegrates.
Seed coat then surrounds embryo and wings develop for dispersal
Pine Life Cycle:
(Vodopich and Moore, pg 307)
Leaves arranged in bundles (fascicles)
Female (Ovulate) Cones
Immature female cones (winter)
Male (Staminate) cones
- woody plants that produce seeds
- resemble palms
- dioecous
- male and female cones
- insect pollinated
- Zamia genus in the US
- variation in trunk length
- life cycle similar to other gymnosperms
Zamia Male strobilus
Zamia Female Stobili
flowering plants
angiosperm = seeds in a fruit
vascular seed plants
produce reproductive structures - flowers and fruits
differ from gymnosperms in that they produce seeds which are enclosed in ovaries
as they develop
roses, peas, sunflowers,
oaks and maples
lilies, orchids, grasses
(corn, wheat) and palms
sporophyte generation dominates the life cycle
ovary develops into a fruit
ovules develop into seeds
flower produces microspores that are contained within pollen grains and the egg
develops within the ovules
Fertilization (double) involves the release of pollen that sticks to the stigma and
then a pollen tube grows down the style toward the ovules releasing 2 sperm
1 of the sperm fertilizes the egg to forming a diploid zygote (2n) which will
develop into a seed
the second sperm unites with the large center cell (polar nuclei) of the female
gametophye resulting in a triploid (3n) cell which develops into the endosperm
(surrounds the embryo and provides nutrition for the seed until it can
photosynthesize on its own)
Life cycle of a typical angiosperm
- protect developing bud
Petals (corolla)
- function to attract pollinators
- anther and filament
- microspores and microgametophytes are produced within the anther.
- will become seeds
- contain megasporangium within which the megaspores are produced by meiosis
- the megaspores produce megagametophytes, which, in turn, produce eggs
- the stigma, style, and ovary
- the bottom portion of a pistil
- contains ovules
- enlarges and becomes the fruit and the ovules become seeds
- flower stalk
- male parts of the plant
- female parts of the plant
Plants: Reproduction
A) Flowers
Flower Type/Ovary Position:
Ovary is inferior; sepals,
petals and stamens are
on top of the ovary
Floral parts fuse
halfway to the
Ovary is superior; sepals,
petals and stamens are
inferior to the ovary
Flower Symmetry:
Radial (Actinomorphic)
Bilateral (Zygomorphic)
1. Wind
2. Insect
Flower Pollination and Fertilization:
- 4 microsporangia in each anther
- each microsporangia produce microspore mother cells that undergo meiosis to
produce 4 pollen grains per microsporocyte
microsporocytes fall apart and the microspores are released
each microspore divides and produces a pollen vegetative and a generative cell
generative cell divides again to produce 2 sperm
double fertilization in the ovary – zygote and an endosperm
Life Cycle of the Flower:
(Vodopich and Moore, pg 316)
ovary develops into a fruit and ovules develop into seeds
flower produces microspores that are contained within pollen grains and the egg
develops within the ovules
Fertilization (double) involves the release of pollen that sticks to the stigma and
then a pollen tube grows down the style toward the ovules releasing 2 sperm
1 of the sperm fertilizes the egg to forming a diploid zygote (2n) which will
develop into a seed
the second sperm unites with the large center cell (polar nuclei) of the female
gametophye resulting in a triploid (3n) cell which develops into the endosperm
(surrounds the embryo and provides nutrition for the seed until it can
photosynthesize on its own)
B) Seeds
- mature ovule
- three main parts:
a seed coat - develops from the integument of the ovule
a storage area (the endosperm) - food
a dormant embryo
(Vodopich and Moore, pg 341)
Proembryo stage
zygote divides to form a mass of cells = embryo
embryo consists of a basal cell, suspensor, and a two-celled proembryo
suspensor is the column of cells that pushes the embryo into the endosperm
Globular stage
Cell division of the proembryo leads to the globular stage
radially symmetrical
little internal cellular organization
Heart-shaped stage
Division of the globular stage produces bilateral symmetry and two cotyledons
cotyledons store digested food from the endosperm
tissue differentiation begins
root and shoot meristems appear
Torpedo stage
cotyledons elongate
precambial tissue appears (develops into vascular tissue)
Mature embryo
has large bent cotyledons on either side of the stem apical meristem
radicle (forms root) has a root apical meristem and a root cap (as root pushes
through the soil, the outer (older) cells of the root cap are sloughed off and
replaced by new cells from the root apical meristem)
hypocotol = region between apical meristem and radicle
endosperm is depleted and food is stored in the cotyledons
epicotyl = region between the attachment of cotyledons and stem apical meristem
Mature Embryo – Torpedo Stage
Monocot and Dicot Seeds:
(Vodopich and Moore, pg 342)
C) Fruits:
ripened ovaries
ovary wall develops into fruit wall from the carpels (one or many)
ovules develop into seeds
“true fruits”
“false fruits”
berries = aggregate fruits, dry fruits at maturity and then breaks open - fruit =
ovary wall can develop into a fruit of different layers, including an inner one that
is stony—a drupe (like a peach)
when the ovaries of separate flowers fuse together to they form a compound or
multiple fruit, such as a pineapple
parthenocarpy = absence of seeds
possible to examine a fruit to determine the ovary’s position in the flower
- if scars or parts of old petal and sepals are at the tip of the fruit, the
flower was inferior (apple) and if at the base then superior (orange)
A) Pericarp - external part of a fruit which surrounds the seed
1. exocarp
2. mericarp
3. endocarp
B) Seed
 Fleshy Fruits
Simple fruits
- from a single ovary
- flesh mostly of ovary tissue
a) endocarp hard and stony; ovary superior and single-seeded
(cherry, olive, coconut): drupe
b) endocarp fleshy or slimy; ovary usually many seeded (tomato,
grape, green pepper): berry
- flesh mostly of receptacle tissue (apple, pear, quince): pome
Complex fruits
- from more that 1 ovary
a) fruit from many carpels on a single flower (strawberry,
raspberry);: aggregate fruit
b) fruit from carpels of many flowers fused together (pineapple):
multiple fruit
 Dry Fruits
- fruits that split open at maturity (usually more than one seed)
a) split occurs along two seems in the ovary. Seeds borne on one
of the halves of the split ovary (pea and bean pods, peanuts):
b) seeds released through pores or multiple seams (poppies, irises,
lilies): capsule
- fruits that do not split open at maturity (usually one seed)
a) pericarps hard and thick, with a cup at its base (acorn, chestnut):
b) pericarp thin and winged (maple, ash, elm): samara
c) pericarp this and not winged (sunflower, buttercup): achene
(cereal grains): caryopsis
D) Stems:
holds up leaves – important for photosynthesis
holds up flowers for pollination
xylem carries water and minerals up from roots to the leaves
phloem takes food back down to be stored and distributed as needed
herbaceous – green, flexible and has notches where leaves develop
woody - covered by bark, have scars where twigs and fruit have dropped off and
have small openings for transpiration
primary growth occurs from the apical meristems of shoots and roots  apical
secondary growth – increase in girth (diameter) of stems and roots (especially
woody plants)  lateral growth
Woody Stems:
(Vodopich and Moore, pg 333)
leaf structure have been optimized for photosynthesis
o a flat surface for maximum exposure to sunlight
chloroplasts are concentrated on upper surface to receive maximum
exposure to sunlight
 stomata regulate the entry of CO2 into the leaf and air spaces inside the
leaf permit rapid diffusion
 water is pulled into the leaf from the roots by transpiration, the
evaporative loss of water from leaf surfaces
expanded, photosynthetic portion of the leaf = a blade/lamina.
between lamina and stem there may or may not be a stalk = petiole
all leaves have a bud where they attach to the stem - a bud defines a leaf, no
matter what type of leaf it is
no apical meristem therefore that are determinate – limited growth
simple or compound
simple if a leaf has one lamina
compound if it has more than one lamina (individual laminas = leaflets
if all the leaflets arise from the same point on the petiole, the leaf = palmate
if the leaflets occur in pairs along the central stalk, the leaf = pinnate
the arrangement of leaves on a stem = phyllotaxy
Leaves may be arranged in three ways:
 alternate - 1 leaf per node
 opposite - 2 leaves per node
 whorled - 3 or more leaves per node
1. Epidermis
outer layer of cells
upper and lower epidermis
covered by a cuticle, a waxy or fatty layer, that functions to reduce water loss
usually only one cell thick
stomata = specialized epidermal structures
 consist of a pair of guard cells that form a pore for gas exchange
 open and close in response to environmental clues
 may occur on both leaf surfaces, but are more numerous on the
lower surface
2. Mesophyll
mesophyll = "middle leaf"
ground tissue of the leaf
contains air spaces for the diffusion of gases
chloroplasts for photosynthesis
2 layers in dicots:
Palisade mesophyll
cells = chlorenchyma (parenchyma cells with chlorophyll) and are
tightly packed, columnar cells
photosynthetic activity takes place here therefore, there are more
chloroplasts than in the spongy layer
Spongy mesophyll
Cells = parenchyma and are irregularly shaped and less compact –
appear "spongy"
photosynthetic activity is lower than in the palisade layer
3. Vascular bundles
xylem towards the upper surface of leaf
phloem towards lower surface of leaf
vascular tissues of veins are enclosed by parenchyma cells or compactly arranged
bundle sheath cells
- ensures that the vascular system is not exposed to the air and that
all substances entering and leaving the vascular tissues must pass
through the sheath
veins of dicots are usually bordered by collenchyma or sclerenchyma for strength