C-Fern Lab Report

I have been swamped with work as the end of my chemistry, biology, and anatomy courses approaches!

In lieu of a new Blog post, I am publishing my lab report for the C-Fern experiment. Enjoy! (My baby sporophytes are thriving happily in their water bottle terrarium!)

Interested in learning more about C-Ferns? Follow this link.


I. Description of Observations

a. First Period (Day 0)
On the first day of the C-Fern experiment we used pipettes to transfer spores (in solution) from their original container to prepared petri dishes with agar growing medium. Using the dropper, we placed three drops onto the agar, and then used a sterile spore spreader to distribute them across the surface. With our dish labeled and placed into the plant receptacle, we were done.

b. Second Period (Day 5-7)
By the second lab period the spores had begun to grow. We had some of different sizes and shapes, but most were similar to the “mitten hand” or heart shaped silhouette. This lab day was primarily about observation and identification of recognizable structures, such as rhizoids.

c. Third Period (Day 10-14)
The third lab period was the most exciting! On this day we used a mere five drops of sterile water to flood our gametophytes and induce sexual reproduction. At first nothing seemed to happen, but with a better-focused microscope it was possible to see improbably small dark dots whizzing around the dish. These sperm were using water to make the arduous trek from the antheridia to the archegonia. They appeared to dance about with a meandering pathway, but ultimately wound up figuring out where to go. In a few minutes the activity slowed down as most of the sperm that had been released found their way to the archegonia.

d. Fourth Period (Day 19-21)
By the fourth lab period, most of the gametophytes had eggs that had been fertilized by sperm. It was possible to add more sterile water and release a few more sperm to make their liquid voyage, but most were already safely docked in the archegonia. From this point forward we hydrated and observed the growth of the sporophyte plants. I am very proud of our baby C-ferns! I placed some of the plants I took home into a small water bottle terrarium, and am keeping them moist with deionized water. My sporophytes have continued to slowly grow in size.

II. Description of the Fern Life Cycle

We began our observation of the fern life cycle with haploid spores. These single cells germinated and became multicellular gametophytes. The gametophytes, in turn, produced male and female gametes (sex cells). With the presence of water it was possible for the male gametes, sperm, to leave the antheridia and travel to the eggs in the archegonia. There fertilization was completed, and the diploid sporophyte was born. Once mature, the sporophytes are capable of producing the haploid spores via meiosis, completing the cycle.

III. Questions regarding the experiment

a. How do sperm find and reach the egg in the archegonium?

The sperm uses chemotaxis to locate the archegonia, and it requires water so that it can swim to reach the eggs.

b. Why do gametophytes die after the sporophyte starts to grow?

The young sporophytes predate the gametophytes as a nutrient source when they are first developing.

c. What factors would influence self-fertilization of hermaphroditic (bisexual) gametophytes versus cross-fertilization from the male gametophyte in the archegonium on the hermaphroditic gametophyte?

Cross-fertilization is encouraged by the separation of antheridia and archegonia on the hermaphroditic gamete. Self fertilization might be more likely to occur in the absence of male only gametophytes, or if individual hermaphroditic gametophytes were isolated.

d. What are the genetic consequences of sporophytes produced from self-fertilization or hermaphroditic (bisexual) gametophytes versus cross-fertilization from the male gametophyte in the archegonium on the hermaphroditic gametophyte?

Subsequent generations of self-fertilized plants would lack genetic variation, leading to potentially damaging mutations. The descendants of cross-fertilized gametophytes would have a richer genetic library from which to select traits for long-term survival.