8/14/2019 BioD exp 6
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Experiment 6: Gymnosperm and Angiosperm
Gymnosperms
Characteristics:
1. Do not produce flower or fruit.
2. Include plants with ovules not enclosed in carpel (naked
seed).3. Absence of companion cells in phloem.
4. Heterosporous, producing microspores that develop into pollen
grains and
megaspores that are retained in an ovule.
5. Fertilized by pollination through agents such as insects and
wind.
6. Divided into four divisions: (i) Pinophyta (Pinus)(ii)
Ginkgophyta (Ginkgo)
(iii) Cycadophyta (Cycad)(iv) Gnetophyta (Gnetum, Ephedra,
Welwitschia)
7. Cycads and Ginkgohave motile sperms that swim directly to the
egg inside the ovule,
whilst conifers and gnetophytes have sperms with no flagella.
Their sperms reach the
egg cell by apollen tube that grows through ovule tissue.8. Pine
is the most commonly studied gymnosperm. In pine, the male cone has
modified
leaves called microsporophylls. Each microsporophyll bears a
microsporangium within
which the microspores are produced. The microspore divides and
grows to form a four-
nucleus male gametophyte which is known as pollen. A grain of
pine pollen has two
large air sacs to make it buoyant in the wind. The female cone
has scales called
megasporophylls that produce megaspores. During pollination, a
pollen tube will grow
from the pollen to transport the sperm to the egg cell.
Figure 1: Figure 2:
The male cone of pine The female cone of pine
Angiosperms
Characteristics:1. Flowering plants.
2. Have closed carpel enclosing the ovule.
3. Presence of companion cells in phloem
4. Heterosporangous, which produce pollens in stamen and ovules
in carpel.
5. Double fertilizations: one sperm cell fuses with the egg cell
forming the diploid
zygote (2n) whilst another fuses with the polar nuclei (mostly
two) forming a triploid
(3n) endosperm nucleus. After double fertilizations, each ovule
develops into a seed.
6. Divided into two classes: (i) Magnoliopsida (Dicots)
(ii) Liliopsida (Monocots)
7. Seeds with two cotyledons are called dicots (e.g., bean)
whilst seeds contain only a
single cotyledon are monocots (e.g., corn).
1
http://en.wikipedia.org/wiki/Heterosporoushttp://en.wikipedia.org/wiki/Microsporeshttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Megasporeshttp://en.wikipedia.org/wiki/Cycadhttp://en.wikipedia.org/wiki/Ginkgohttp://en.wikipedia.org/wiki/Ginkgohttp://en.wikipedia.org/wiki/Coniferhttp://en.wikipedia.org/wiki/Gnetophytehttp://en.wikipedia.org/wiki/Flagellahttp://en.wikipedia.org/wiki/Pollen_tubehttp://en.wikipedia.org/wiki/Carpelhttp://en.wikipedia.org/wiki/Dicotyledonhttp://en.wikipedia.org/wiki/Monocotyledonhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Plants.html#DicotsAndMonocotshttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Plants.html#DicotsAndMonocotshttp://en.wikipedia.org/wiki/Heterosporoushttp://en.wikipedia.org/wiki/Microsporeshttp://en.wikipedia.org/wiki/Pollenhttp://en.wikipedia.org/wiki/Megasporeshttp://en.wikipedia.org/wiki/Cycadhttp://en.wikipedia.org/wiki/Ginkgohttp://en.wikipedia.org/wiki/Coniferhttp://en.wikipedia.org/wiki/Gnetophytehttp://en.wikipedia.org/wiki/Flagellahttp://en.wikipedia.org/wiki/Pollen_tubehttp://en.wikipedia.org/wiki/Carpelhttp://en.wikipedia.org/wiki/Dicotyledonhttp://en.wikipedia.org/wiki/Monocotyledonhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Plants.html#DicotsAndMonocotshttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Plants.html#DicotsAndMonocots
