Seed orchard production of Chamaecyparis nootkatensis (D. Don) Spach seed faces several challenges including low seed production, pollen-cone abortion, self-pollination, and accelerated reproductive development. In a seed orchard study in 1988 and 1989, approximately eight seeds were produced per cone, but only one to three seeds per cone contained viable embryos. Pollen-cone abortion in 21 clones ranged from 6 to 87% in 19891990 and from 0 to 6% in 19901991. A bud mite, identified as Trisetacus chamaecypari Smith, was consistently associated with pollen-cone abortion in two orchard locations. This mite may be the cause or simply a symptom of unhealthy pollen cones. In a pollination study involving wind, self, and cross pollinations on five clones, self-pollinated cones had significantly fewer seeds containing embryos (4%) compared with the other treatments (2833%). Pollen-cone development at a seed orchard occurred in July and August 1990 and was comparable with natural stand phenology. However, embryo development was significantly accelerated, with embryos at a seed orchard substantially larger than embryos at the natural stand at comparable times.
Taxus brevifolia Nutt. has a reduced ovulate structure that consists of a single ovule in a leaf axil instead of a compound ovulate strobilus. Taxus brevifolia on southern Vancouver Island, British Columbia, were studied over three seasons. Proembryos occurred from mid-May to mid-June. They underwent four free nuclear divisions forming 16 nuclei before cellularization. Early embryos were present from mid-May to mid-August. Simple polyembryony was observed up to the massive embryo stage, and differential growth of the embryonal cells was interpreted as incomplete cleavage polyembryony. Mid-embryos were present from mid-June to late August and had a distinct protoderm and focal zone. Late embryos were visible from mid-July onwards. Carbohydrates began accumulating at the early embryo stage, whereas proteins and lipids accumulated in the late embryo stage. The presence of a red aril corresponded to increased amounts of lipid in the megagametophyte cells. Individual seeds matured from July until November. The seed efficiency ranged from 0 to 16% and averaged 5%. Prezygotic loss was the most common fate of ovules, followed by postzygotic loss. Possible causes of this poor seed efficiency are poor pollination success, insect damage, or light limitation.
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