Transcript Cycads

Scientific name: Cycas
Found in the Jurassic period of
the Mesozoic era.
(250-145 million years ago)
They can grow in
Subtropical and Tropical
climates.
They grow in any type of
soil; mostly moist habitats.
185 different species of
Cycads
Gymnosperms
naked
seed
Four major living groups.
Cycads (Cycadophyta),
Welwitschia group (Gnetophyta),
Ginkgo, the Maiden Hair Tree (Ginkgophyta),
and the conifers (Pinophyta) .
Cycas bougainvilleana
Cycads
Cycads resemble palms or tree-ferns in overall
appearance but differ greatly in detailed structure
and reproductive behaviour. Cycads are dioecious
(i.e. male and female reproductive structures are
borne on separate plants), and reproduction is by
seeds produced on open carpophylls or seedbearing leaves. Although technically woody plants,
unlike other woody plants, cycads have a thick, soft
stem or trunk made up of mostly storage tissue with
very little true wood.
The living cycads include about 250 species, with 11
genera in 3 families.
Microcycas calocoma Photo Dennis Stevenson
Female coneCuban species
Cycas-Circinate vernation of young foliage leaf
Cycas-Coralloid root
T.S. Leaflet of Cycas
Cycas- T.S. Microsporophyll
Cycas- Young ovule
Cycas- Megasporophyll with young ovule
Cycas- Mature ovule
Cycas- Mature ovule
The microspores develop
into pollen grains.
This female
gametophyte is
developed from the
megaspores.
*the dominant lifecycle stage is the sporophyte.
Sporophyte relies on gametophyte for a period of
time to develop into a seed.
Life Cycle of the Cycads
Male reproductive stucture,
pollen is dispersed by wind or
insects to female reproductive
structure. (haploid)
gynostrobilus grows a
pollen tube, sperm cell
swims through pollen tube
using its tail, or flagella.
(haploid )This fertilizes the
egg and it becomes a
zygote. (Dipoid)
Zygote develops into
an embryo then a
seed is developed in
a coat that originates
from the ovary.
(diploid)
Development of the
microspores and
megaspores through
meiosis (haploid)
Then the tree
grows! (diploid)
Economic and health benefits of Cycads
•Some cycads are poisonous as a result there
are not many medical benefits
•These are also very close to extinction
•If prepared correctly they can be eaten
•The nuts contain a nerve toxin
•Consumption of the starch derived from cycads
is a factor in the development of Lytico-Bodig
disease, a disease symptoms similar to
Parkinson's and ALS.
•But they look kinda pretty!!
Thank You…