The International Online Journal of Science and Mathematics Education

The Development and Validation of a Classroom Environment Scale for Filipinos

Classroom Psychosocial Environment

Antheridial Development from the Isolated Protoplast
of Young Gametophyte of Tree Fern Cyathea
contaminans (Hook) Copel.: A Scientific Approach
to Teaching about Spermatogenesis

Rodolfo S. Treyes, Toshiyuki Kawakami & Hideo Ikeda
Faculty of Education,
Hiroshima University,
Higashi-Hiroshima,
739-8523 Japan

AbstractIntroductionMaterials & MethodsResults
ReferencesAppendix

Discussion

Spermatogenesis in ferns was one of the points of interests for in-vitro investigation using protoplast isolation techniques. Studies have been conducted on the isolation of protoplasts from the young Lygodium japonicum sporophyte from which gametophytes were produced, and antheridium and archegonium were developed (Nakamura & Maeda, 1994; Maeda, Sugimoto, Nakamura, Masuda, Kaneko, & Sugai, 1990). This paper describes the antheridial development of the isolated primordial cells isolated from young gametophytes of the tree fern Cyathea contaminans.

Young prothallia that had not yet attained their heart-shaped characteristics were used for protoplast isolation. This ensured that only the tissues containing the immature antheridial primordial cells were present. The isolated antheridial primordial cells (average diameter = 35mm) exhibited some prominent morphological features: its cytoplasm contained granulated structures and fewer chloroplasts, its translucent nucleus was located off-center within the cytoplasm, and its nucleolus was at the center of the nucleus. The protoplast was mostly colorless.

The development of the antheridium from the isolated protoplast can easily be observed even without fixing the tissue. Spermatogenous cell division was synchronous within the fixed antheridium stained with 2% acetic-orcein solution. Hoffman and Vaughn (1995) earlier reported that cell division was synchronous within each developing antheridium.

Naff (1979) reported that antheridia formed in gametophyte cultures treated with GA₃ in several fern species except in species of the family Cyatheaceae. In this study, the preliminary experiment using GA₃ on Cyathea contaminans produced the same negative result. But in the actual experiment, GA₇ hastened antheridial development of isolated protoplasts of the antheridial primordial cells. No antheridia were formed in protoplasts in a GA₇-free (control) culture media. Approximately 50% of the antheridial primordial protoplasts obtained by enzymatic isolation were found to be viable.

Students of biology can use the findings we obtained as background information for their own investigations. They can use fern gametophytes for protoplast investigation. Since the fern prothallus is made up of only one layer of cells the isolation process will not be too complicated. They can easily observe antheridial development using live specimens.

The entire processes of cell differentiation and spermatogenesis of the fern C. contaminans were analyzed by light microscopy, photographed, and developed into slides. Using these slides, students can observe the details of (a) the living protoplasts, (b) the differentiation of antheridia from a primordial cell, (c) the process of spermatogenesis, (d) the opening of the antheridial cap cell, and (e) the release of spermatozoids. The slides can also be used as supplementary material in teaching the above-mentioned concepts. The slides can be used to teach a lesson on “observing mitosis in the process of spermatogenesis” to provide students a clear understanding of the developmental stages of fern spermatozoids. The lesson can be done using a “scientific-approach-to-teaching” to allow students to understand and believe in the processes occurring in a living system of an organism. The lesson can stimulate students’ curiosity and lead them to use the following method of analysis in their search for an explanation:

Formulate a question, e.g., How do antheridia and spermatozoids develop?
Propose preliminary explanations to answer the question. The explanations should include hormonal influence, mitosis, and cell differentiation.
Formulate predictions (hypotheses) based on the assumed truth of one or more postulates of the explanations. For example, If a certain hormone influences antheridial development, then spermatogenesis can be induced by the action of that hormone.
Gather evidence by observing the colony of fern gametophytes in a low-density culture and a high-density culture, taking into consideration the existing data on gibberellin-treated culture.
Compare evidence from the different cultures to find out which prediction (hypothesis) is supported or contradicted by the evidence.

The lesson will not only enable students to observe the reaction of the cultures to a given hormone, it will also improve their understanding of the nature of science and develop their critical and analytical thinking skills. A sample lesson is given in Appendix A.

The sample lesson can help students comprehend scientific methods, which involves understanding and applying a large set of interrelated skills—problem identification, hypothesis formulation, experimental design, implementation, data collection, analysis and synthesis, and communication of results. Cyathea contaminans is one of the fern species with a limitless potential for classroom use. It can provide a condition for inquiry-centered learning in the classroom and for independent student research. In general, the experimental procedures used in this study may be applied to any fern that commonly grows in the surroundings.

AbstractIntroductionMaterials & MethodsResults
ReferencesAppendix