Understanding dormancy mechanisms in fruit crops and seed stratification

Aim of the experiment: To understand the dormancy mechanism in fruit crops and to undertake seed stratification.

Objective: To understand the mechanisms of dormancy in fruit crops and demonstrate seed stratification techniques for breaking dormancy.

Apparatus required:

Petri dishes, moist sand, filter paper, refrigerator, seeds of different fruit crops, fungicide, beakers, measuring cylinders.

Theory:

Dormancy is a temporary suspension of visible growth in plant structures containing a meristem. In fruit crops, dormancy ensures survival under adverse environmental conditions. Seed dormancy can be physiological or physical. Stratification is a method of breaking dormancy by exposing seeds to cold and moist conditions, simulating winter.

There are three main types of dormancy:

                                i.            Physical Dormancy: Caused by impermeable seed coats.

                              ii.            Physiological Dormancy: Due to internal hormonal imbalances.

                            iii.            Morphological Dormancy: When embryo development is incomplete.

Stratification involves subjecting seeds to a period of chilling to satisfy the cold requirement necessary for germination. It is widely practiced for temperate fruit crops such as apple, pear, and peach.

Procedure:

i.                    Collect healthy and mature seeds from selected temperate fruit crops.

ii.                  Clean the seeds thoroughly to remove any pulp and debris.

iii.                Prepare a fungicide solution and treat the seeds for 5–10 minutes.

iv.                Take a clean container or Petri dish and fill it with moist sand or place a double layer of moist filter paper inside.

v.                  Place the treated seeds evenly inside the medium.

vi.                Cover and seal the container to retain moisture.

vii.              Keep the setup inside a refrigerator maintained at 4°C.

viii.            Monitor the setup weekly for signs of radicle emergence.

ix.                After the stratification period, transfer germinated seeds to soil trays for further observation.

Observations:

Week	No of Seeds Taken	No. of Seeds Germinated	Temperature (°C)	Germination Percentage (%)	Remarks
1
2
3
4
5

Result:

Stratification effectively broke the dormancy of temperate fruit crop seeds, as indicated by radicle emergence within __ weeks.

Assignments:

a)      What is dormancy and why is it significant in fruit crops?

b)      Explain the role of stratification in dormancy breaking.

c)      List fruit crops that require seed stratification.

d)      What are the different types of dormancies?

e)      How does temperature influence the dormancy period?