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Glime, J. M. 2017. Ecophysiology of Development: Gametogenesis. Chapt. 5-8. In: Glime, J. M. Bryophyte Ecology. Volume 1. 5-8-1 Physiological Ecology. Ebook sponsored by Michigan Technological University and the International Association of Bryologists. Last updated 17 July 2020 and available at <http://digitalcommons.mtu.edu/bryophyte-ecology/>. CHAPTER 5-8 ECOPHYSIOLOGY OF DEVELOPMENT: GAMETOGENESIS TABLE OF CONTENTS Definition ............................................................................................................................................................ 5-8-2 Developmental Stages ......................................................................................................................................... 5-8-2 Environmental Factors ........................................................................................................................................ 5-8-2 Water Availability ........................................................................................................................................ 5-8-2 Gametangium Developmental Need for Water ..................................................................................... 5-8-3 Swimming Sperm ................................................................................................................................. 5-8-3 Paraphyses ............................................................................................................................................ 5-8-6 Photoperiod and Light Intensity ................................................................................................................... 5-8-6 Nutrients ..................................................................................................................................................... 5-8-12 pH............................................................................................................................................................... 5-8-14 Temperature ............................................................................................................................................... 5-8-15 Environmental Signalling Interactions ....................................................................................................... 5-8-15 Hormones .......................................................................................................................................................... 5-8-16 Environmental Hormone Interactions ........................................................................................................ 5-8-17 Sugars ................................................................................................................................................................ 5-8-17 Overall Physiology ............................................................................................................................................ 5-8-17 Color Changes ................................................................................................................................................... 5-8-18 Delay of Gametogenesis.................................................................................................................................... 5-8-18 Male vs Female ................................................................................................................................................. 5-8-19 Differential Survival .................................................................................................................................. 5-8-20 Bisexual Gametangial Differentiation ........................................................................................................ 5-8-21 Hormonal Regulation of Gender ................................................................................................................ 5-8-21 Dwarf Males ............................................................................................................................................... 5-8-22 Different Controls ...................................................................................................................................... 5-8-22 Numbers of Gametangia ............................................................................................................................ 5-8-24 Gender Recognition .......................................................................................................................................... 5-8-24 Fertilization ....................................................................................................................................................... 5-8-25 Self-incompatibility ................................................................................................................................... 5-8-25 Geographic and Habitat Relationships .............................................................................................................. 5-8-27 Tradeoffs – Cost of Reproduction ..................................................................................................................... 5-8-30 Summary ........................................................................................................................................................... 5-8-31 Acknowledgments ............................................................................................................................................. 5-8-32 Literature Cited ................................................................................................................................................. 5-8-32 5-8-2 Ecophysiology of Development: Gametogenesis CHAPTER 5-8 ECOPHYSIOLOGY OF DEVELOPMENT: GAMETOGENESIS Figure 1. Antheridial splash cups of Polytrichum juniperinum. Photo by Janice Glime. Definition Gametogenesis – the development of gametes (genesis stages, it produces a stalk, then the two-sided apical cell means origin) is the essential process leading to sexual gains a third cutting face and the archegonium develops reproduction. In bryophytes, gametes are produced by from this cell. The antheridial development is similar to mitotic division of tissue within multicellular structures, the that of other mosses. This chapter will examine the antheridia (male) and archegonia (female), collectively interaction of hormones and the environment as they known as gametangia. The location of these structures on influence this development. the mosses is the basis for dividing the mosses into two large groups, the acrocarpous mosses that produce Environmental Factors archegonia at the tips of upright stems, and the The timing of the induction of gametangia is a critical pleurocarpous mosses that produce archegonia on side function in the life cycle of bryophytes. For sexual branches of a generally horizontal stem. The differences in reproduction to be successful, gametangia must form at a location of these archegonia can present differences in the time when they can survive and they must mature at a time ease with which the sperm can reach the archegonium, and when it is safe and sufficient water is present for the sperm hence reach the egg. to reach the egg. This timing is controlled by external Developmental Stages signals in the environment, and this is interpreted internally through such controls as hormones and nutrient levels. Lal and Bhandari (1968) described the developmental stages of the sex organs of the moss Physcomitrium Water Availability carpathicum. The archegonium begins its development in Gametogenesis (development of gametes) must be a manner similar to that of the antheridium. In these early timed in such a way as to take advantage of the most Chapter 5-8: Ecophysiology of Development: Gametogenesis 5-8-3 critical need in fertilization – water. Because sperm in Sphagnum (Figure 4) provides a good example of bryophytes must swim to the archegonium, adequate water effect of water on gametangial maturation. Sundberg is critical, but too much water or rapidly flowing water may (2002) studied nine sites in Sweden for six years, during dilute or carry off the sperm and make directional which the nine most abundant species produced capsules. movement toward the archegonium all but impossible. In Capsule production related most to moisture regime of the fact, timing of moss reproduction, whether a response to previous summer, with more precipitation resulting in more day length or temperature or other environmental stimulus, capsules. This presumably relates to success of is often related to the season of proper moisture. Since gametangial formation. Capsule success in wetter pits gametangial initiation can occur several (or many) months related positively to spring precipitation in the same year as prior to the actual time of fertilization, environmental cues capsule production, suggesting it was also important for other than moisture must trigger the process. It is therefore fertilization success. Further discussion of timing of an expected consequence that different species within a reproduction with moisture availability is in the phenology genus respond to different environmental cues for chapter. gametogenesis, permitting them to live in different habitats. And even within species, populations can differ widely (Clarke & Greene 1970). But for many bryophytes, water is an important signal for gemetangia to develop, perhaps because it permits the gametophyte to be active and
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