caa a22 4500 475817788 CHVBK 20180406123813.0 cr unu---uuuuu 170329e20000901xx s 000 0 eng 10.1007/s004970000042 doi (NATIONALLICENCE)springer-10.1007/s004970000042 Western white pine ( Pinus monticola Dougl.) reproduction: I. Gametophyte development [Elektronische Daten] [John N. Owens, Darla Bruns] Abstract : Male and female gametophyte development are described from light and transmission electron microscope preparations of ovules from first and second year Pinus monticola Dougl. seed cones. In the first year of development, pollen tubes penetrate about one-third the distance through the nucellus. The generative cell and tube nucleus move into the pollen tube. The megagametophyte undergoes early free nuclear division. First-year seed cones and pollen tubes become dormant in mid-July. In the second year, seed cones and pollen tubes resume development in April and the pollen tubes grow to the megagametophyte by mid-June. Early in June the generative cell undergoes mitosis, forming two equal-size sperm nuclei that remain within the generative cell cytoplasm. The generative cell has many extensions and abundant mitochondria and plastids. The megagametophyte resumes free nuclear division, then cell wall formation begins in early July. Cell wall formation and megagametophyte development follow the pattern found in other Pinaceae. Three to five archegonial initials form. The primary neck cell divides, forming one tier of neck cells. Jacket cells differentiate around each central cell. The central cell enlarges and becomes vacuolate; then vacuoles decrease in size and the cell divides, forming a small ventral canal cell and a large egg. Plastids in the central cell engulf large amounts of cytoplasm and enlarge. This process continues in the egg, and the peripheral cytoplasm of the egg becomes filled with transformed plastids. Mitochondria migrate around the nucleus, forming a perinuclear zone. The wide area of egg cytoplasm between these two zones has few organelles. A modified terminology for cells involved in microgametophyte development is recommended. Springer-Verlag Berlin Heidelberg, 2000 Key words White pine nationallicence Pinus nationallicence Megagametophyte nationallicence Egg nationallicence Microgametophyte nationallicence Sperm nationallicence Owens John N. Centre for Forest Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia V8W 3N5, Canada e-mail: jowens@uvic.ca Fax: +1-250-721-6611, CA aut Bruns Darla Centre for Forest Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia V8W 3N5, Canada e-mail: jowens@uvic.ca Fax: +1-250-721-6611, CA aut https://doi.org/10.1007/s004970000042 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s004970000042 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Owens John N. Centre for Forest Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia V8W 3N5, Canada e-mail: jowens@uvic.ca Fax: +1-250-721-6611, CA aut NATIONALLICENCE 700 1- Bruns Darla Centre for Forest Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia V8W 3N5, Canada e-mail: jowens@uvic.ca Fax: +1-250-721-6611, CA aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer