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Life in the Garden:how do the plants populate their environment (2)?
Tuesday 8 July 2008
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JPEG Life in the Garden:how do the plants populate their environment (2)?

- flowerless plant breeding
- seedless and sporeless plant breeding

NOTIONAL OBJECTIVES :

To know that, among the flowerless plants, organs (spore cases) produce spores that sprout and are at the origin of a new flowerless plant.

METHOD OBJECTIVES :

- to understand information from a text and observations
- to make a preparation and use a microscope
- to create observation drawings

MATERIALS :

- polypode leaves (fern)
- prothallus with young fern
- microscope
- slides and coverglass
- droppers
- thin pliers

PROCEDURES :

1. Observe moulds grown in class: notion of spore and spore case

Suggest the pupils to make mouldy a piece of bread for a few days by keeping it damp.
They notice first a white felting covering the bread: it is white mould.
A few days later, with the microscope, they see filaments each ended by a black ball: the spore case (or sporangium). It contains tiny spores.
Set up some spore cases between the slide and the coverglass, without water, then with a water drop.
Sketch the observations.

2. Observe spores and fern spore cases (polypodies)

“The spore cases appear on the lower side of the polypode leaves. Each spore case bursts when it comes to maturity and frees many spores taken away by the wind."

- Take with thin pliers a few fern spore cases. Set them up between the slide and the coverglass. Push gently on the coverglass so as to make the spore cases burst and observe them through the microscope.
- Make an observation sketch.

3. Spore evolution after their dispersal

“Each spore fallen on the ground sprouts and gives birth to a pluricellular filament. It turns quickly into a heart-shaped leaf on which a new fern grows."
From the text, develop a schema of the fern development cycle.
Seedless and sporeless plant breeding
The spore and seed dispersal permits the life environments to become populated. Do plants have other means of colonizing their life space?

NOTIONAL OBJECTIVES :

To know that plants can multiply without seeds nor spores, thanks to the existence of specialised or non-specialised organs.

METHOD OBJECTIVES :

- to understand information from observations and texts
- to grow plants by cuttings

MATERIALS :

- plants in pot (geranium, strawberry plant, periwinkle…)
- compost or vermiculite
- bottom-pierced flower pots
- small dish or bowl

PROCEDURES :

- Experiment vegetative multiplication without specialised organs
- Cut the end of a young leafy geranium stem (about 10 cm). You have a cutting: a plant element that, after having been split from the plant, gives a new individual. Put the cuttings in a flower pot containing compost or vermiculite.
- Water regularly and in a moderate amount. Observe the cutting evolution for several weeks.
- Experiment vegetative multiplication with specialised organs

“In the summer, the strawberry plants produce runners, sort of aerial creeping stems whose end takes root, giving birth to new strawberry plants."

With the text, colour the schema below:

Un fraisier {JPEG}

- the strawberry plant at the start in green
- the new strawberry plant in yellow
- the runners in red

Give a title to the sketch.

Write a short text showing the function of the vegetative organs in the environment being populated by the plants.

ASSESSMENT :

1. Observation sketches

For each observation sketch, make an assessment of the following elements:

- well-centered drawing with respected proportions
- continuous and clean lines
- right captions with horizontal recall lines
- observation conditions and scale mentioned
- general care

2. Compare a flower plant breeding to the fern breeding by completing the table below:

Fern Flower plants

Sprouting element

Sprout result

3. Complete the following text:

Among plants, the … dispersal and sprouting for flower plants and the … dispersal and sprouting for the flowerless plants permits the colonization and populating of an environment.

However, other means exist like the specialized … formation like the … for example which give birth to new individuals.


Jean-Michel Josse professeur de Sciences de la Vie et de la Terre, Lycée Français Charlemagne de Pointe Noire, Congo Brazzaville

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