Stephen G. Saupe - Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; (320) 363-2782; ssaupe@csbsju.edu

Gink & Go Study Seed Germination

Setting:  Gink is sitting at his desk with his calculator staring at some data tables and grumbling.  Go enters the room.
Go:   Hey Gink, whazzup?  You seem a little out of sorts.
Gink:   You bet I am.  I can�t figure out how to analyze the data from the stupid seed experiment that we did in Saupe�s class.
Go:   Don�t worry, I can help you because I just finished my calculations in the library. 
Gink:   Jeez, you�re almost as big a geek as Saupe.
Go:   Whoa, if you expect me to help you you�d better�
Gink:   Sorry.  Anyway, what is this germination percentage and germination rate stuff?
Go:   Remember our experiment?  We put 100 lettuce seeds in a Petri dish lined with filter paper moistened with water. 
Gink:   Yeah, yeah, and then we put the dishes in the dark at 24 C and returned every day to count the number of seeds that had germinated.
Go:   Right � if the radicle had emerged from the seed, we said it had germinated. 
Gink:   Well, I understand all that, but the calculations confuse me.
Go:   Don�t worry.  Let�s see your data table.
Gink:   Here it is�.(check it out)

  

Table 1:  Germination of Gink�s Lettuce Seeds
1. Days since start 2. # Seeds Germinated During Time Interval

3. Percent Germination during time interval (per day)

 4. Total Seeds Germinated Since To

5. Cumulative Percent Germination

0 0      
1 20      
2 50      
3 15      
4 5      
5 1      
6 2      
7 0      

 

Go:   To start, you have to calculate the number of seeds that germinate during each time interval by dividing the number that germinated on that day by the total number of seeds, which was 100 seeds.
Gink:   And then you multiply by 100 to convert to a percent. 
Go:   Right.  Complete column #3
Gink:   Okay, but now we have to calculate total seeds that germinate since To.  What�s that all about.
Go:   Simple, all we need to do is keep a running total of the seeds that germinated on each of the days. 
Gink:   Oh, I get it.  So on the first day the total is 20 and on the 2nd day the total is 20 + 50, or 70.  Right?
Go:   Perfect.  Complete column #4.
Gink:   And for last column we simply divide the total seeds that germinated by 100 and multiply by 100. 
Go:   Now you�re cooking � or should I say, germinating.   Complete column #5
Gink:   Let�s see your data now.  (Complete Go�s data table)

 

Table 1:  Germination of Go�s Lettuce Seeds
1. Days since start 2. # Seeds Germinated During Time Interval

3. Percent Germination during time interval (per day)

 4. Total Seeds Germinated Since To

5. Cumulative Percent Germination

0 0      
1 10      
2 10      
3 45      
4 15      
5 10      
6 3      
7 1      

 

Go:   We still have to do one more thing.
Gink:  

Right...it's time to watch �Friends.�
Go:   No...we have to graph percent germination during time interval vs. days since start.
Gink:   Oh right.  But, please don�t tell me that we have to graph cumulative percent germination vs. days, also.
Go:   That�s right.  (complete these graphs on the paper provided for both Gink�s & Go�s data)

Analysis:

  1. Whose seeds germinate fastest?
  2. Whose seeds have the most uniform (synchronous) germination?
  3. Whose seeds have the greatest germination percentage?
  4. Whose seeds are better?  Explain.
  5. What signals the beginning of germination?
  6. Some seeds failed to germinate during the experiment.  Suggest possible explanations.
  7. Are lettuce seeds dormant or quiescent?
  8. Explain why you might hypothesize that these seeds require light to germinate.  Do the data support this hypothesis?

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Last updated: January 03, 2004   
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