Example of an investigation

Aim

To find out the ideal length of time to stratify peach stones to break dormancy to increase the rate of germination.

Stratification is a method of pre-treating some seed types by exposing them to cold, moist conditions for a period of time. This cold, moist period copies natural processes such as frosty, wet winter soil conditions. It softens the seed coat, triggers the seed embryo to start growing and breaks down or removes chemicals that may stop or slow up germination. The soft seed coat allows water to enter to start the germination process.

Hypothesis

Stratified peach stones will germinate faster than unstratified peach stones. Those that have been stratified for the longest period of time will germinate faster than the others.

Equipment needed:

Windfall peach stones from peaches that have ripened and fallen off the tree onto the ground below the tree.

four hundred windfall peach stones
moist peat/pumice mix
refrigerator
4 containers, one for each trial
prepared seedbeds outside.

Windfall peach stones come from peaches that have ripened and fallen off the tree onto the ground below the tree.

Control

The unstratified seed.

Variable to be changed

The length of time the seeds are left at 5°C

A 100 peach stones for 120 days
B 100 peach stones for 100 days
C 100 peach stones for 40 days
D 100 peach stones were not stratified

Variables kept the same

the cultivar of peach stones (the same type or variety of peach, for example Golden Queen)
where the peach stones were collected
the temperature they were stratified at – 5°C
the type of material the peach stones were placed in during stratification
all were stratified in the same refrigerator.

Method

Four hundred windfall peach stones were collected. Four containers were partially filled with a 50:50 mix of moist peat and pumice. 100 stones (peach seeds) were spread out evenly into each container. They were then covered with a layer of peat/pumice. The containers were covered with cling film that had holes in. The film kept in the moisture but the holes in the film allowed air into the container.

The containers were labelled and placed as follows:

120 days and placed in the fridge
100 days and placed in the fridge
40 days and placed in the fridge
unstratified (placed at room temperature).

At the beginning of spring the various treatments were removed from cold storage and sown into labelled beds outside. The numbers of seeds that germinated were counted at 10 day intervals.

Results

The following results were recorded of the percentage that germinated.

	0 days	10 days	20 days	30 days	40 days	50 days	60 days
A	0	3	37	60	68	70	71
B	0	2	37	43	46	50	50
C	0	0	0	0	2	9	10
D	0	0	0	0	0	0	0

A labelled line graph is drawn from the data collected.

Labelled line graph from data collected about stratification of peach seeds.

Conclusion

Chilling assists the germination process in windfall peaches. The longer the peach stones were stratified, the faster the germination rate once they were planted.

What's next?

Go to: 5 Practice investigation.