Ceratopteris Richardii: The Effects of Increasing Spore Density in Detecting Higher Percentages of Sexually Expressed Gametes

Ceratopteris richardii: The effects of increasing spore density in detecting higher percentages of sexually expressed gametes.

Abstract:

The Ceratopteris genus is a model plant system in allowing the study of life and reproductive cycles of spores, allowing for spore to gamete cellular and physical observation. The triangle water fern, Ceratopteris richardii, provided for visual identification of this transition. Spores of different densities were inoculated, cultured, and observed in germination and sexual expression. We estimated higher spore densities increase percentages of sexually expressed gametes, male and hermaphrodite; and concluded that spore density has a direct effect on germination and sexual expression numbers. The ability to observe the spore to gamete transition leads to opportunity in manipulation of gametes for biological studies related to vascular plants.

Introduction:

The model use of the homosporous Ceratopteris richardii (C-Fern) provides for high accessibility and understanding of its life and reproductive cycles, both haploid and diploid (2, 3.) The life and reproductive cycles of the sporophyte are easily observable under a compound microscope; and volume harvesting and culturing of spores for experimental studies are relatively easy due to the quick life cycle of the Ceratopteris at 120 days or less (4.) Spore life and reproductive cycle summary consists of spore germination, gametophyte differentiation, pheromone antheridiogen sexual differentiation, embryonic development, through to spore maturation (Fig. 1.) Male or hermaphrodite gametes, of the Ceratopteris, are determined by the pheromone antheridiogen or ACE. This pheromone is responsible for stimulating the determination of male gametes and is secreted from the hermaphrodite gametes. This allows for a ratio of males to hermaphrodite gametes to vary depending on the spore density (Fig 3, 4) (5.)

We estimated that higher spore densities will generate higher amounts of gametes and sexually expressed gametes, several spore densities were cultured to ascertain the percentages of gamete production. The higher the spore density, the increased amount in the germination rate of gametes; allowing for volume culturing, harvesting, and manipulation of gametes for sexual expression in biological studies (2.)

Materials and Methods:

The initial week, six different densities of C-fern spore medium were inoculated into six separate Petri dishes, labeled A-F, with A containing the highest C-fern spore density. Upon inoculation, each of the Petri dishes were sampled for spore density by using a dissecting microscope, and spore densities were recorded in Table 1. This procedure was repeated during several laboratory sessions. The second week, it was discovered that there was contamination exposure within the source vials of spore density medium, after identifying evidence of contamination within the inoculated Petri dishes. The third week specific matched groups of Petri dishes, identified as having no visual indication of the contamination, were then collected and analyzed for the experiment. The C-fern spores were observed and visually identified, using a compound microscope at 100 times magnification, to identify the developing gametophytes. The dissection microscope was then used to visually identify the number of germinating gametophytes, and their numbers were then recorded into Table 1. Upon the fourth week, the gametophytes were visually identified for variances in sexual development and expression, using a compound microscope at 400 times magnification. Individual quantities of both mature hermaphroditic gametophytes and mature male gametophytes were then recorded in Table 1. The recorded data was entered into Microsoft Office Excel, and an ANOVA: single factor was completed to determine any significant changes.

Results:

Ceratopteris