High Humidity Low Humidity Flat Soil Agar Control Agar Agar


□ Total # Archegonia ■ % Archegonia on Dorsal Surface

Figure 9.7 Effect of relative humidity on archegonia production in gametophytes of Pteridium aquilinum. High humidity, 100%; low humidity, approximately 90%. Results are averages of three replicates for each treatment; the number per replicate is 20 individuals. Bars are means ±1 standard error.

Experiments indicated that gametophytes in high humidity cultures produce a large percentage of archegonia (48.7%) on the dorsal side of the thal-lus, whereas the low humidity cultures produced very few archegonia (1.4%) on the dorsal surface (Figure 9.7). Perhaps of greater significance, the total numbers of archegonia produced increased nearly four-fold in low relative humidity cultures, compared to high humidity cultures, and nearly two-fold relative to typical flat agar cultures (grown in small culture boxes not within terraria). The total number of archegonia produced by low humidity cultures mimicked the results of cultures grown on soil. Since it was necessary to add water to the soil cultures periodically to prevent them from dying (whereas it was not necessary to add water to agar cultures) it may be that soil cultures experienced lower relative humidities at least part of the time.

A unifying theme may explain both the anomalous production of archego-nia on the dorsal surface and the lower total numbers of archegonia produced in standard agar cultures. Both appear to be induced by reduced light and humidity differentials across the gametophyte's two surfaces relative to that experienced by gametophytes in nature. Though relatively simple anatomically and morphologically, fern gametophytes do have complex differentiation patterns including establishment of polarities in development (Raghavan, 1989). It may be that the strong differentials of light and moisture between dorsal and ventral surfaces experienced by gametophytes in natural habitats provide environmental signals critical to establishment of normal polarity. Incomplete establishment of this polarity in agar cultures may disrupt normal differentiation such that archegonia are produced in abnormal positions and overall in smaller numbers.

Additional experiments may elucidate further the environmental signals and physiological responses involved, but it is clear from these experiments that gametophytes grown in standard agar cultures in Petri dishes may yield seriously misleading data relative to sexual development of natural populations of fern gametophytes. Analysis of breeding systems of fern species based on laboratory data should take these discrepancies into consideration.

9.5 Summary

Every fern and lycophyte population owes its beginnings to the gameto-phyte generation and the simple gametophyte plant contains the same genetic information that produces the highly complex sporophyte plant. We should not be surprised to find that sophisticated differentiation of form and physiology also exists among gametophytes of different taxa. Studies described in this chapter have made it clear that combinations of growth rate, mature form, sexual differentiation, longevity, and differential physiological interactions with environmental parameters lead to functional gametophyte strategies that initiate the sporophyte phase of each species in its preferred habitat. Without knowledge of these gametophyte-level strategies we cannot comprehend habitat compartmen-talization within fern and lycophyte communities or migration, distribution, and evolution of species.

The simplistic "one size fits all" depiction of the cordiform, bisexual fern gametophyte in standard textbooks does a great disservice not only to ferns and lycophytes, but to the disciplines of ecology, genetics, and evolution as well. The thoughtful student is left to conclude, incorrectly, that ferns and lycophytes do not obey principles of variation and selection and can be set aside as inexplicable curiosities in the broader context of plant evolution.

Data derived from laboratory cultures provide important starting points for ecological studies but must not be surrogate to field investigations. Laboratory cultures do not provide information on ecological safe sites, on interaction with competing vegetation, or on conditions necessary for successful sporo-phyte recruitment. Data from culture studies may, in fact, yield misleading data. Absence of field data on recruitment leaves the haunting prospect, as expressed by Peck (1980) in his field studies, that gametophytes we study in the field could be nothing more than "reproductive noise." Determining which gametophytic ecological and reproductive strategies result in sporophytes capable of completing the life cycle remains a challenge that must be accepted.

Both short-term studies of habitat characterization and population demographics, including sexual structure, and long-term studies on sporophyte recruitment and population dynamics of perennial gametophytes need to be conducted on a broad scale. Functional classes of ecological strategies will likely be redefined from such studies. However, we must be cautious in extrapolation. We must not assume a priori that the gametophyte ecology of a given species is representative of another in the same genus or habitat any more so than is the ecology of the sporophyte generation. These studies will challenge the next generation of fern and lycophyte biologists, but they are sure to increase immensely our insight into the occurrence, survival, and evolution of species.


Alpert, P. (2000). The discovery, scope, and puzzle of desiccation tolerance in plants. Plant Ecology, 151, 5-17.

Alpert, P. and Oliver, M. J. (2002). Drying without dying. In Desiccation and Survival in Plants, ed. M. Black and H. W. Pritchard. Wallingford: CAB International, pp. 3-43.

Andersson, I. (1923). The genetics of variegation in a fern. Journal of Genetics, 13, 1-11.

Atkinson, L. R. (1973). The gametophyte and family relationships. In The Phylogeny and Classification of Ferns, ed. A. C. Jermy, J. A. Crabbe, and B. A. Thomas. New York: Academic Press, pp. 73-90.

Atkinson, L. R. and Stokey, A. G. (1964). Comparative morphology of the gametophyte of homosporous ferns. Phytomorphology, 14, 51-70.

Bewley, J. D. (1979). Physiological aspects of desiccation tolerance. Annual Review of Plant Physiology and Plant Molecular Biology, 30, 195-238.

Bierhorst, D. W. (1953). Structure and development of the gametophyte of Psilotum nudum. American Journal of Botany, 40, 649-658.

Bierhorst, D. W. (1966). Fleshy cylindrical subterranean gametophyte of Schizaea melanesica. American Journal of Botany, 53, 123-133.

Bjorkman, O. and Demmig, B. (1987). Photon yield of O-2 evolution and chlorophyll fluorescence characteristics at 77-K among vascular plants of diverse origins. Planta, 170, 489-504.

Bower, F. O. (1923). The Ferns, Vol. I. Cambridge: Cambridge University Press.

Brodribb, T. J. and Holbrook, N. M. (2004). Stomatal protection against hydraulic failure: a comparison of coexisting ferns and angiosperms. New Phytologist, 162, 663-670.

Campbell, D. H. (1905). The Structure and Development of the Mosses and Ferns. New York: Macmillan.

Chiou, W.-L. and Farrar, D. R. (2002). The mating systems of some epiphytic Polypodiaceae. American Fern Journal, 92, 65-79.

Chiou, W. L., Farrar, D. R., and Ranker, T. A. (1998). Reproductive biology of some species of Elaphoglossum. Canadian Journal of Botany, 76, 1967-1977.

Chiou, W.-L., Farrar, D. R., and Ranker, T. A. (1999). Gametophyte growth and sexual reproduction of some epiphytic ferns. In Ching Memorial Volume - A Collection of Pteridological Papers Published to Commemorate the Centenary of the Birth of Professor Ren-Change Ching, ed. X.-C. Zang and K.-H. Shing. Beijing: China Forestry Publishing House, pp. 303-315.

Cousens, M. I. (1979). Gametophyte ontogeny, sex expression, and genetic load as measures of population divergence in Blechnum spicant. American Journal of Botany, 66, 116-132.

Cousens, M. I. (1981). Blechnum spicant: habitat and vigor of optimal, marginal, and disjunct populations, and field observations of gametophytes. Botanical Gazette, 142, 251-258.

Cousens, M. I. (1988). Reproductive strategies of pteridophytes. In Plant Reproductive Ecology: Patterns and Strategies, ed. J. Lovett-Doust and L. Lovett-Doust. Oxford: Oxford University Press, pp. 307-328.

Cousens, M. I., Lacey, D. G., and Kelly, E. M. (1985). Life-history studies of ferns - a consideration of perspective. Proceedings of The Royal Society of Edinburgh Section B, Biological Sciences, 86, 371-380.

Cousens, M. I., Lacey, D. G., and Scheller, J. M. (1988). Safe sites and the ecological life history of Lorinseria areolata. American Journal of Botany, 75, 797-807.

Dassler, C. L. and Farrar, D. R. (1997). Significance of form in fern gametophytes: clonal, gemmiferous gametophytes of Callistopteris baueriana (Hymenophyllaceae). International Journal of Plant Sciences, 158, 622-639.

Dassler, C. L. and Farrar, D. R. (2001). Significance of gametophyte form in long-distance colonization by tropical, epiphytic ferns. Brittonia, 53, 352-369.

Dopp, W. (1962). Eine die Antheridienbildung bei Farnen fordernde Substanz in den Prothallien von Pteridium aquilinum (L.) Kuhn. Berichte der Deutschen Botanischen Gesellschaft, 63, 139-147.

Emigh, V. D. and Farrar, D. R. (1977). Gemmae: a role in sexual reproduction in the fern genus Vittaria. Science, 198, 297-298.

Farrar, D. R. (1967). Gametophytes of four tropical fern genera reproducing independently of their sporophytes in the southern Appalachians. Science, 155, 1266-1267.

Farrar, D. R. (1976). Spore retention and release from overwintering fern fronds. American Fern Journal, 66, 49-52.

Farrar, D. R. (1985). Independent fern gametophytes in the wild. Proceedings of the Royal Society of Edinburgh, 86, 361-369.

Farrar, D. R. (1998). The tropical flora of rockhouse cliff formations in the eastern United States. Journal of the Torrey Botanical Club, 125, 91-108.

Farrar, D. R. and Gooch, R. D. (1975). Fern reproduction in Woodman Hollow, central Iowa: preliminary observations and a consideration of the feasibility of conducting studies on fern reproductive biology in nature. Proceedings of the Iowa Academy of Science, 82, 119-122.

Gaff, D. F. (1987). Desiccation tolerant plants in South America. Oecologia, 74, 133-136.

Goebel, K. (1905). Organography of Plants. Oxford: Clarendon Press.

Greer, G. K. and McCarthy, B. C. (1999). Gametophytic plasticity among four species of ferns with contrasting ecological distributions. International Journal of Plant Sciences, 160, 879-886.

Hagar, W. G. and Freeberg, J. A. (1980). Photosynthetic rates of sporophytes and gametophytes of the fern, Todea barbara. Plant Physiology, 65, 584-586.

Hamilton, R. G., Lloyd, R. M. (1991). Antheridiogen in the wild. The development of fern gametophyte communities. Functional Ecology, 6, 804-809.

Haufler, C. H. and Adams, W. W. (1982). Early gametophyte ontogeny of Gleichenia bifida (Willd.) Spreng. - phylogenetic and ecological implications. American Journal of Botany, 69, 1560-1565.

Hietz, P. and Briones, O. (1998). Correlation between water relations and within-canopy distribution of epiphytic ferns in a Mexican cloud forest. Oecologia, 114, 305-316.

Hiyama, T., Imaichi, R., and Kato, M. (1992). Comparative development of gametophytes of Osmunda lancea and Osmunda japonica (Osmundaceae) -adaptation of rheophilous fern gametophyte. Botanical Magazine (Tokyo), 105, 215-225.

Hofmeister, W. (1862). On the Germination, Development, and Fructification of Higher Cryptogamia. London: Ray Society.

Holttum, R. E. (1938). The ecology of tropical pteridophytes. In Manual of Pteridology, ed. F. Verdoorn. The Hague: Martinus Nijhoff, pp. 420-450.

Kappen, L. (1964). Untersuchungen uber die Jahreslauf der Frost-, Hitze-und

Austrocknungsresistenz vin sporophyten einheimischer Polypodiaceen. Flora, 155, 123-166.

Kiss, J. Z. and Swatzell, L. J. (1996). Development of the gametophyte of the fern Schizeae pusilla. Journal of Microscopy, Oxford, 181, 213-221, Part 2.

Lloyd, R. M. (1974). Mating systems and genetic load in pioneer and nonpioneer Hawaiian pteridophyta. Botanical Journal of the Linnean Society, 69, 23-35.

Lovis, J. D. (1977). Evolutionary patterns and processes in ferns. In Advances in Botanical Research, ed. R. D. Preston and H. W. Woolhouse. London: Academic Press, pp. 229-440.

Makgomol, K. and Sheffield, E. (2001). Gametophyte morphology and ultrastructure of the extremely deep shade fern, Trichomanes speciosum. New Phytologist, 151, 243-255.

Mesler, M. R. (1975a). Gametophytes of Ophioglossum palmatum L. American Journal of Botany, 62, 97-98.

Mesler, M. R. (1975b). Mature gametophytes and young sporophytes of Ophioglossum nudicaule. Phytomorphology, 25, 156-166.

Mesler, M. R. (1976). Gametophytes and young sporophytes of Ophioglossum crotalophoroides Walt. American Journal of Botany, 63, 443-448.

Mesler, M. R. and Lu, K. L. (1977). Large gametophytes of Equisetum hyemale in northern California. American Fern Journal, 67, 97-98.

Miller, J. H. (1968). Fern gametophytes as experimental material. Botanical Review, 34, 361-440.

Moore, J. P., Nguema-Ona, E., Chevalier, L., Lindsey, G. G., Brandt, W. F., Lerouge, P., Farrant, J. M., and Driouich, A. (2006). Response of the leaf cell wall to desiccation in the resurrection plant Myrothamnus flabellifolius. Plant Physiology, 141, 651-662.

Naf, U. (1979). Antheridiogens and antheridia development. In The Experimental Biology of Ferns, ed. A. F. Dyer. London: Academic Press, pp. 435-470.

Nayar, B. K. and Kaur, S. (1969). Types of prothallial development in homosporous ferns. Phytomorphology, 19, 179-188.

Nayar, B. K. and Kaur, S. (1971). Gametophytes of homosporous ferns. Botanical Review, 37, 295-396.

Nester, J. E. and Schedlbauer, M. D. (1981). Gametophyte development in Anemia mexicana Klotzsch. Botanical Gazette, 142, 242-250.

Nobel, P. S. (1978). Microhabitat, water relations, and photosynthesis of a desert fern, Notholaena parryi [Pteridophyta]. Oecologia, 31, 293-309.

Oertli, J. J., Lips, S. H., and Agami, M. (1990). The strength of sclerophyllous cells to resist collapse due to negative turgor pressure. Acta Oecologica, International Journal of Ecology, 11, 281-289.

Oliver, M. J. (1996). Desiccation tolerance in vegetative plant cells. Physiologia Plantarum, 97, 779-787.

Ong, B. L. and Ng, M. L. (1998). Regeneration of drought-stressed gametophytes of the epiphytic fern, Pyrrosia piloselloides (L.) Price. Plant Cell Reports, 18, 125-228.

Ong, B. L., Koh, C. K. K., and Wee, Y. C. (1998). Effects of CO2 on growth and photosynthesis of Pyrrosia piloselloides (L.) Price gametophytes. Photosynthetica, 35, 21-27.

Peck, J. H. (1980). The ecology and reproductive biology of ferns in Woodman Hollow, Iowa. Unpublished Ph.D. Thesis, Iowa State University, Ames, IA.

Peck, J. H., Peck, C. J., and Farrar, D. R. (1990). Comparative life history studies and the distribution of pteridophyte populations. American Fern Journal, 80, 126142.

Pickett, F. L. (1913). Resistance of the prothallia of Camptosorus rhizophyllus to desiccation. Bulletin of the Torrey Botanical Club, 40, 641-645.

Pickett, F. L. (1914). Some ecological adaptations of certain fern prothallia -

Camptosorus rhizophyllus Link., Asplenium platyneuron Oakes. American Journal of Botany, 1, 477-498.

Pickett, F. L. (1931). Notes on xerophytic ferns. America Fern Journal, 21, 49-57.

Porembski, S. and Barthlott, W. (2000). Granitic and gneissic outcrops (inselbergs) as centers of diversity for desiccation-tolerant vascular plants. Plant Ecology, 151, 19-28.

Proctor, M. C. F. and Pence, V. (2002). Vegetative tissues: bryophytes, vascular resurrection plants and vegative propagules. In Desiccation and Survival in Plants:

Drying Without Dying, ed. M. Black and H. W. Prichard. Wallingford: CAB International, pp. 207-237.

Raghavan, V. (1989). Developmental Biology of Fern Gametophytes. New York: Cambridge University Press.

Ranker, T. A. and Houston, H. A. (2002). Is gametophyte sexuality in the lab a good predictor of sexuality in nature? Sadleria as a case study. American Fern Journal, 92, 112-118.

Remy, R. and Remy, W. (1980). Devonian gametophytes with anatomically preserved gametangia. Science, 208, 295-296.

Remy, R., Gensel, P. G., and Hass, H. (1993). The gametophyte generation of some early Devonian land plants. International Journal of Plant Science, 154, 35-58.

Rumsey, F. J., Vogel, J. C., Russell, S. J., Barrett, J. A., and Gibby, M. (1998). Climate, colonisation and celibacy: population structure in central European Trichomanes speciosum (Pteridophyta). Botanica Acta, 111, 481-489.

Sakai, A. (1980). Freezing resistance of gametophytes of the temperate fern, Polystichum retroso-paleaceum. Canadian Journal of Botany, 58, 1144-1148.

Sato, T. and Sakai, A. (1981). Cold tolerance of gametophytes of some cool temperare ferns native to Hokkaido. Canadian Journal of Botany, 59, 604-608.

Schneider, E., Schuettpelz, E., Pryer, K. M., Cranfill, R., Magallon, S., and Lupia, R. (2004). Ferns diversified in the shadow of angiosperms. Nature, 428, 553-557.

Skelton, C. L. (2007). Investigations into gametophyte morphology and population sex ratios through direct comparisons between laboratory grown and field-grown fern gametophytes. Unpublished MS Thesis, Iowa State University, Ames, IA.

Smith, A. R., Pryer, K. M., Schuettpelz, E., Korall, P., Schneider, H., and Wolf, P. G. (2006). A classification for extant ferns. Taxon, 55, 705-731.

Stokey, A. G. (1951). The contribution of the gametophyte to the classification of the homosporous ferns. Phytomorphology, 1, 39-58.

Stokey, A. G. and Atkinson, L. R. (1958). The gametophyte of the Grammitidaceae. Phytomorphology, 8, 391-403.

Tausz, M., Hietz, P., and Briones, O. (2001). The significance of carotenoides and tocopherols in photoprotection of seven epiphytic fern species of a Mexican cloud forest. Australian Journal of Plant Physiology, 28, 775-783.

Taylor, T. N., Kerp, H., and Hass, H. (2005). Life history biology of early land plants: deciphering the gametophyte phase. Proceedings of the National Academy of Sciences of the United States of America, 102, 5892-5897.

Tryon, R. M and Vitale, G. (1977). Evidence for antheridiogen production and its mediation of a mating system in natural populations of fern gametophytes. Botanical Journal of the Linnean Society, 74, 243-249.

Twiss, E. M. (1910). The prothallia of Anemia and Lygodium. Botanical Gazette, 49, 168-181.

Voeller, B. and Weinberg, E. S. (1969). Evolutionary and physiological aspects of antheridium induction in ferns. In Current Topics in Plant Science, ed. J. E. Gunckel. London: Academic Press, pp. 77-93.

Walp, R. L. (1951). Fern prothallia under cultivation for 12 years. Science, 113, 128-129.

Watkins, J. E., Jr. (2006). Comparative functional ecology of tropical ferns. Unpublished Ph.D. Thesis, University of Florida, Gainesville, FL.

Watkins, J. E., Jr., Cardelus, C., Colwell, R. K., and Moran, R. C. (2006a). Species richness and distribution of ferns along an elevational gradient in Costa Rica. American Journal of Botany, 93, 73-83.

Watkins, J. E., Jr., Kawahara, A. Y., Leicth, S. A., Auld, L. R., Bicksler, A. J., and Kaiser, K. (2006b). Fern laminar scales protect against photoinhibition from excess light. America Fern Journal, 96, 83-92.

Watkins, J. E., Jr., Mack, M. C., and Mulkey, S. S. (2007a). Gametophyte ecology and demography of epiphytic and terrestrial tropical ferns. American Journal of Botany, 94, 701-708.

Watkins, J. E., Jr., Mack, M. C., Sinclair, T. R., and Mulkey, S. S. (2007b) Ecological and evolutionary consequences of desiccation tolerance in tropical fern gametophytes. New Phytologist, 176 , 708-717.

Was this article helpful?

0 0
10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook

Post a comment