Experimental Biology / Krauss

November 14, 1998

Damian Verutes

The Effects of Freezing Seeds on Plant Growth for Smooth Pea, Sweet Corn, Barley and Morning Glory.

Introduction

In a previous study we germinated several seed types and recorded their progress, as far as how many germinated, change in texture, and change in length. The seeds we used had been dried and most (if not all) had to be soaked overnight before they could be germinated. I assumed the reason the seeds had been dried was for storage and shipping purposes. This got me to thinking if seeds could be frozen and stored over a long period of time to later be planted. This would have applications for space colonizing, so seeds could be transported to other planets and then planted. I decided to pose the question "Can seeds be frozen (to store for later use) and then grow as healthily as seeds which werenít frozen?" My hypothesis was that the seeds would become dormant and one thawed the frozen seeds would grow just as well as the seeds which werenít frozen because in nature seeds must survive extremes in temperature. This is proven by the cycle of seasons by which seeds fall to the ground in autumn, are frozen during the winter, and then grow in the spring.

Methods and Materials

For this experiment the materials needed are: 8 (16 oz.) plastic cups, approx. 260g potting soil per cup (2080 g total),6 Smooth Pea, 6 Morning Glory, 6 Barley, and 6 Sweet Corn seeds (24 total), 8 labels, a marking pen, a freezer, a ziplock bag, plastic wrap, a plastic trough large enough to fit all 8 cups, a metal prong, greenhouse lights and water.

Before starting my experiment I placed half of the seeds (3 Smooth Pea, 3 Morning Glory, 3 Barley, and 3 Sweet Corn) in the ziplock bag, and placing the bag in the freezer, froze them for approx. 24 hours. I next labeled 4 of the 8 cups the name of the seeds it would contain and "experimental." (i.e.. "Sweet Corn Experimental") I labeled the other four cups in a similar fashion replacing "experimental" with "control." Using a heated metal prong I poked 3 holes in the bottom of each cup which would allow excess water to drain out. I put approx. 260g of soil in each cup (loosely packed) and planted 3 seeds of each type in the appropriate cup, putting 3 frozen Morning Glory seeds in the cup labeled "Morning Glory Experimental," and 3 unfrozen Morning Glory seeds in the cup labeled "Morning Glory Control," etc. I placed all of the now labeled cups in a large plastic trough which would collect excess water, and placed the trough under greenhouse lights. I watered the cups twice a week on Tuesdays and Thursdays with 50 ml of water for each cup and covered the trough with plastic wrap by the end of the day on Thursday to make sure the plants retained moisture over the weekend. I had also set up petri dishes the same way as the cups but found that the seeds were all rotted and did not include them in my experiment. I also set up soil control cups with 3 seeds of each type just to measure the pH of the soil (using a soil pH meter) and rule it out as a variable. I poked holes in 4 plastic cups the same way as previously mentioned, used the same amount of soil and watered them as frequently. For each seed type I got an average pH of 7 so I decided not to include them in this report since pH was not an issue. I also later uprooted all of my plants being careful not to lose any of the roots and took their final mass so I could compare the final mass of the varibles to the final mass of the controls.


Results

The data show that all of the 3 seeds of each type germinated except for the frozen Morning Glory, for which 2 seeds germinated, the control Morning Glory, for which 2 seeds germinated, and the control Barley plant, for which only 1 seed germinated.

The data also show that except for pea all of the frozen specimens grew even taller than the controls, and all contained more mass, and were therefore further developed than the controls, except barley which had .1g less mass than the cotrol.

*Also see attached charts and graph

Discussion

The data show that except for pea all of the frozen specimens grew taller and except for barley had more mass than the control seeds, and the barley had only .1g less mass than the cotrol, a difference which I hardly feel is significant, and in the case of the pea, both pea specimen were hard to measure because they had leaves sprouting in every direction so due to this I may have made a mistake in recording their height and the difference in height is probably less. The outcome that the experimental seeds would grow as well seems logical since plants, in nature grow after being frozen over in the winter and grow in the spring, but the fact that they grew even taller and were further developed is astounding. However, as much as I want to say the data prove my hypothesis I cannot in good conscience. In designing my experiment I neglected to have several groups of control and experimental plants, and due to time constraints could not repeat my experiment so the results I got could have just been a fluke which is why I must deem my experiment inconclusive. Another flaw in my experiment is that I froze the seeds for only 24 hours. It does not seem fair to conclude the seeds could be frozen for a month and grow as well. Perhaps a better experimental design would have been to freeze the seeds for several longer periods of time and see the impact on plant growth. It was also mentioned to me that a T-Test could be done to see whether or not my results were significant by seeing if the difference in data were due to my experiment but I was not certain how this would apply to my experiment since I was trying to prove there should be no difference in data. Also because I had limited access to the computer program I would need to perform a T-Test and had no way to perform one due to time constraints no T-Test was performed.

 

Conclusion

I decided my results were inconclusive and that the experiment could be redone with more groups of specimens at different rates of freezing and the seed growth averaged to have conclusive results. Again, the reason my results must be deemed inconclusive is because I had only 1 group of controls and one group of variables, my results arenít accurate. Had I set 3 or 4 groups of controls and variables the height measured for each seed type would have been averaged, making my results very accurate. The results I got for only one group of varibles and one group of controls may have been an anomaly making my data and results of my experiment inaccurate.