Kingdom plantae IGSCSE
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Transcript of Kingdom plantae IGSCSE
Kingdom PlantaeExtended
Divisions
The plant Kingdom is divided into Divisions rather than Phyla
We only need to know about:
The Ferns and
Angiosperms (flowering plants)
Mosses (for interest only)
Mosses are small plants that only grow in damp areas because they do not have a cuticle to stop them drying out
They so not have proper leaves, stems or roots
Ferns (Pteridophytes)–
you need to know about these
These plants dominated the world when dinosaurs were around but are not so common now
They have a cuticle so can grow in dryer areas
They have true roots and stems with xylem and phloem to transport water and sugars
They spread using rhizomes that grow away from the parent plant
The leaves are called frondsThese grow by unfurling from fiddleheads
Fern life cycle - there are 2 stages
The plant we see is the sporophyte
These have a full set of chromosomes in their cells
We call this 2n chromosomes
On the back of the fronds we find sori
Spores are made in these by cell division called meiosis
This gives the spores half the number of chromosomes or n
Spores are released and blown by the wind
When they land in soil they can grow into a tiny microscopic pant called a prothallus
This has only half a set of chromosomes
The prothallus is also called a gemetophyte because it makes gametes (sex cells)
These are made by mitosis so they have half a set of chromosomes
These are like roots
This is a leaf-like structure but is very small
The male and female sex cells fuse to form a new plant with a full set of chromosomes
It grows out of the gametophyte
And becomes an adult sporophyte
Because they are pretty ferns are popular house and garden plants
Gymnosperms (for interest only)
These are plants that reproduce using cones – like Pine Trees
The forests in North America and Europe are mostly coniferous
They have “soft wood” and grow quickly so are grown for paper and furniture
Angiosperms – flowering
Plantsyou need to know this group
Most of the plants we see are angiosperms
They reproduce using flowers (sometimes the flowers are so small we can’t see them)
The plants may be trees, shrubs, grasses, or herbs
All of our important crops are angiosperms
There are two main groups:
Monocotyledons and Dicotyledons
The names of theses groups comes form the number of cotyledons in the seeds
The Cotyledon is a food storage area: Dicotyledons have 2 and Monocotyledons have one
Use this information to start filling in the table on
In fact these days scientists divide the groups by what the pollen looks like
Monocotyledons have one furrow, Dicotyledons have two or more
These pollen grains have been highly magnified by a scanning electron microscope
RootsMonocotyledon roots are fibrous – they branch out just below the soil
This makes plants like grasses useful for holding soil in place and preventing erosion
Dicotyledons tend to have tap roots – this is a long main root with side (lateral) roots coming off it
Dicotyledon roots can go deep into the soil to find water
The next slide has some simple drawings for you to copy
If we look at the roots in cross section we will see:
Monocotyledons have a ring of xylem and phloem and a central pith – this is packing cells or a hollow region
Dicotyledons have the xylem and phloem in the middle
We will learn how xylem carries water and phloem carries sugar later this year
Monocotyledon root T/S
Dicotyledon root T/S
Epidermis
Xylem and Phloem
Pith
Epidermis
Cortex
Xylem and Phloem
Stems
Vascular bundles
monocot
Dicot
Xylem and phloem are grouped together in stems to form vascular bundles
In Monocotyledons the vascular bundles are scattered around
In Dicotyledons they are neatly set in a ring near the edge
Monocotyledon Stem
Dicotyledon Stem
Epidermis
Vascular bundles
Epidermis
Vascular bundles
leaves
monocotyledon
dicotyledon
petiole
One of the easiest ways to tell Monocotyledons from Dicotyledons is by the veins in their leaves. Veins are made of the xylem and phloem
In Monocotyledons the veins are parallel and there is no petiole (stem)
In Dicotyledons the veins are net-like and they have a petiole
Can you work out the magnification of these leaves using the scale bar?
Flowers
We will learn about flowers next year
For now be aware that the flower parts (petals, anthers) come in 3’s in Monocotyledons, and in 4’s or usually 5’s in Dicotyledons
Most monocotyledons are grasses and are wind pollinated so the flowers are really small and not brightly coloured
Check you have filled in the table completely in your notes