Protocol for using Drying Beads to dry seeds

Materials needed:

  • Drying Beads
  • Baking oven, deep baking pan and sturdy gloves, funnel, plastic baskets
  • Moisture-proof metal or plastic containers
  • Seeds: Harvest mature seeds and dry using traditional method first (e.g., sun or air drying)
  • Temperature/humidity meter
  • Small packets of silica gel (optional)

Procedure

1. Reactivation of beads

2. Check bead moisture content (MC) or bead capacity

3. Estimate current moisture content (MC)of the seed

4. Decide final storage MC desired

5.  Calculate bead quantity required for 1 kg seed

Download the latest version of the Drying Beads Calculator.

In the spreadsheet “List”, the weight of beads required is calculated in column H. Multiply this value times the kg of seed to be dried in one container.

6.  Place this amount of beads in a porous bag or container and put it with the seeds inside a moisture-proof container and quickly seal. A small quantity of silica gel in a porous packet can be placed with seed and beads.If the indicator silica gel changes color to indicate a high RH, it would indicate that the container may not be water tight. Reactivate the beads and use again as above (i.e., estimate current seed MC/RH using T/RH meter and determine amount of additional beads needed to reach desired MC/RH). If bead quantity is limiting, step-wise MC reduction should be practiced by re-activating beads between each use.

7. Seed Quality check for storage experiments only: Remove seed samples from three replicates periodically (e.g., at least every three months) and assess seed quality parameters. Put RH/T into each container a day before taking out seed samples and record the both RH and T.

8. Allow large seeds (e.g., corn, soybean, bean, pea) to equilibrate for 5-7 days at ambient conditions before planting if they have been stored with excess beads. Some large seeds are subject to imbibition damage if they are rapidly rehydrated from very low MC caused by use of excess beads, particularly if this occurs at low temperatures. To avoid this, we recommend removing such seeds from the moisture-proof storage and allow them to equilibrate with ambient air for 5-7 days prior to planting. Small horticultural seeds (e.g., lettuce, tomato, onions, etc.) generally are not susceptible to imbibition damage, so this procedure is generally not required for them.

How long can bead dried seeds be stored?

If the seeds are dried to 20-30% RH and stored in a watertight container, cold storage is often not needed for intermediate storage durations. For long-term storage, cold temperatures further extend storage life. Once the seeds are dry, the Drying Beads can be removed, reactivated and reused for other samples, so long as the seeds remain sealed inside of the moisture-proof container.

Although seeds can be stored for many years at ambient temperatures at 20-30% RH, we want to document the viability of dry and control seeds using seed viability constants. Remember desired final RH (cell E3) was used to calculate beads shown in column G (G4:G72) to dry seeds to specific MC (E4 : E72) in the storage.  At p storage days (cell M3), viability  of seeds at MC (Column E4:E72) is predicted (Column M4:M72) based on initial seed germination (cell L3) and seed viability MC (Column H, I) and T (Column J, K) -constants from Seed Information Database (eqn ii).

eq2

 where, v= germination (probit) after storage for p days; Ki = initial germination in probit;  m = seed moisture content in %; T= temperature in °C;  p = storage period in days; KE, CW, CH and CQ  = species specific viability constants.

Universal storage T constants for orthodox seeds have been proposed, i,e., CH = 0.00329 and Cq = 0.000478.

 

Sources:

1. Cromarty AS, Ellis RH, Roberts EH. 1982. The design of seed storage facilities for genetic conservation. IBPGR, Rome.

2. http://data.kew.org/sid/viability/mc1.jsp?oil=47.30&drytemp=25&equib=80&constid=2083

3. Ahuja  KL, Singh  H, Raheja  RK, Labana  KH. 1987. The oil content and fatty acid composition of various genotypes of cauliflower, turnip and radish. Plant Foods for Human Nutrition 37:33-40.

4.  http://hortsci.ashspublications.org/content/44/6/1679.full

5. Seed Science and Technology, Volume 35, Number 2, July 2007 , pp. 432-444(13)

6.  Seed Science and Technology, Volume 39, Number 2, July 2011 , pp. 527-532(6)

7.  http://idosi.org/aejaes/jaes12%282%2912/14.pdf

8. http://www.seedtest.org/upload/cms/user/presentation5Kruseetal.pdf