Cryopreservation: Freezing Plant Tissues

Abstract

Cryopreservation—storing seeds in ultra-cold liquid nitrogen—is one method for maintaining plant genetic stocks in seed banks. Can seeds withstand a really deep freeze and still germinate?

Objective

The purpose of this project is to observe the characteristics and outcomes of cryogenically frozen seedlings over various time periods. This study specifically addresses the cause and effect of the seedling germination rate process.

Credits

April N. Duchanin

Last edit date: 2013-01-10

Introduction

Scientists have been using cryopreservation to build a "living" archive of seed genes. Some of these frozen seeds are kept in storage in the event of natural disasters that may wipe out an important crop. The question remains about seed viability and how long seeds can remain in a frozen state and still germinate to produce a healthy plant.

Terms and Concepts

You should understand the difference between these two areas of study: cryopreservation, cryobiology.
You will need to understand seed structure and germination to understand what impact cryopreservation will have on the seed.
You should also understand exactly what happens to plant tissues when seeds are frozen. What is the process for freezing plant tissue for preservation? What are some of the disadvantages/risks of this process?

Bibliography

What is cryobiology and cryopreservation:

• http://en.wikipedia.org/wiki/Cryopreservation
• http://www.phys.unsw.edu.au/~jw/cryoblurb.html

Impact of cryopreservation on seeds
http://www.wws.princeton.edu/cgi-bin/byteserv.prl/~ota/disk2/1987/8727/872709.PDF

A book offering in depth coverage of research in cryopreservation in plants, including developments in methods for specific species of plants :
Towill, L.E. 2002. Cryopreservation Of Plant Germplasm: Introduction And Some Observations. Pp 3-21. In L.E. Towill And Y.P.S. Bajaj (EDS.)CRYOPRESERVATION Of Plant Germplasm Ii. Biotechnology In Agricultural And Forestry Series Vol 50. Springer, London.

Materials and Equipment

• Seeds. We suggest using the following seeds for this experiment:
  • Supersweet corn
  • Onion
  • Lima bean
  • Cabbage, raddish, broccoli (choose one)
  • Lettuce
• Access to a lab with liquid nitrogen
• Petri dishes
• Cotton rolls
• Water
• Oven

Experimental Procedure

• Suspend the seeds in liquid nitrogen. You should be testing at least four different time durations in the liquid nitrogen. Some suggestions:
  Experiment 1: 1 day
  Experiment 2: 2 days
  Experiment 3: 3 days
  Experiment 4: 4 days
  (Note: you should be testing at least five of each of the seed types in each of your experiments).
• After the appropriate length of time, remove the seeds from the liquid nitrogen.
• Prepare the petri dishes for germination. Cut the cotton slightly smaller than the diameter of the petri dish. Saturate the cotton in the petri dish with water and allow the dish to drain for 5 minutes as excess water will literally drown the seeds.
• Place the seeds in the petri dish and place them in the oven at about 70 to 80 degrees.
• Observe and record the rate of germination for each of the seeds every 24 hours until they are ready for planting.

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