Sexual reproduction in grand fir (Abies grandis)

Publisher Website
Google Scholar
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.