Sexual reproduction in grand fir (Abies grandis)

Abstract

Phenology and anatomy of the postdormancy reproductive phase of Abies grandis Lindl, were studied. The dormant microsporangia contained compactly arranged pollen mother cells (PMC). The pollen cones broke dormancy in the 3rd week of February and soon afterwards the PMC entered meiosis. Microspore tetrads formed by the 2nd week of March. Pollen grains were shed at the five-celled stage in the 3rd week of April. The pollen grains were bisaccate and showed a triradiate mark on the proximal pole. The dormant ovulate-cone buds bore rudimentary ovuliferous scales, each with two ovular areas. Ovulate cones broke dormancy at the end of January. Megaspore mother cells differentiated by the end of February and the integument was initiated soon afterwards. A megaspore triad formed in the 2nd week of April. By the 3rd week of April, at the time of pollination, the ovule contained a free-nuclear gametophyte, and the integument had developed a stigmatic micropylar funnel. Numerous microdroplets were observed on the surface of the funnel to which pollen adhered. After pollination the funnel became infolded, enclosing the pollen grains. Pollen germination, pollen tube growth through the nucellus, and syngamy took only 3–4 days and occurred in the 3rd week of June. The female gametophyte was long and bore two or three archegonia. The proembryo consisted of four tiers of four cells each. The suspensors developed from the subterminal tier of cells. The four terminal cells formed the embryonal mass, whose proximal cells elongated and developed into a secondary suspensor. Differentiation of the root apical meristem and the cotyledons in the young embryo occurred in the 1st week of July and the embryo matured in the 3rd week of August.

Factors affecting seed and cone development in Pacific silver fir (Abies amabilis)

“…Two or three archegonia formed per megagametophyte and each archegonium had two or more tiers of neck cells. This is similar to A. balsamea (Miyake 1903), A. lasiocarpa (Singh and Owens 1981), and A. grandis (Singh and Owens 1982). Megagametophytes occasionally aborted at the early free nuclear stage, as has been reported in many other conifers (Owens and Blake 1985).…”

Genetic diversity and seed production in Santa Lucia fir (Abies bracteata), a relict of the Miocene Broadleaved Evergreen Forest

“…), Pacific silver fir (A. amabilis Dougl. ex Forbes), and subalpine fir all have a low number of filled seeds (Singh and Owens 1982). The percentage of viable seeds in Pacific silver fir may be only 22%; in noble fir (A. procera), 24%; in grand fir, 28%; and up to 38% in subalpine fir (Franklin 1968).…”

“…Ovules in Pacific silver fir and other fir species fully enlarge and develop seed coats in the absence of pollination, resulting in normal appearing but empty seeds (Owens and Molder 1977). Seed chalcids also reduce seed yields in these and other western firs, and were the most important factor in seed loss of grand fir (Singh and Owens 1982). We did not separate seed losses into chalcid-related versus unpredated empty seeds, but the combined loss was over 50% of the crop in the years that we sampled and may be 100% in many years (Talley 1974).…”

Les sécrétions dans la pollinisation des Gymnospermes

“…Les cellules developpent de larges espaces periplasmiques remplis de "granules" de secretion. La nature chimique du secretat n'a pas etc recherchee (Owens et al, 1984 ;Singh et Owens, 1982).…”