Cone and seed development in a wind-pollinated, western hemlock (Tsugaheterophylla) clone bank

1990 ◽  
Vol 20 (9) ◽  
pp. 1432-1437 ◽  
Author(s):  
Anna M. Colangeli ◽  
John N. Owens
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Western Hemlock ◽  
Factors Affecting ◽  
Ovule Abortion ◽  
Cross Pollination ◽  
Seed Cone ◽  
Cone Development ◽  
Empty Seed ◽  
Pollen Cone

Seed and seed-cone development were observed in a wind-pollinated western hemlock (Tsugaheterophylla (Raf.) Sarg.) clone bank in 1983 and 1986. Seed efficiency, the number of filled seed per cone divided by the seed potential, averaged 64% for 58 wind-pollinated clones in 1983 and 20% for 38 clones in 1986. Based on anatomical observations and cone dissections, seed losses resulted from pre- and post-pollination ovule abortion, insufficient pollen, no fertilization, and embryo degeneration. Prepollination ovule abortion, identified by small, flat seed in mature cones, contributed to 11 and 14% reduction in filled-seed yield in 1983 and 1986, respectively. Full-sized but empty seed (lacking an embryo) accounted for 25 and 66% reduction in potential seed yield in the 2 years, respectively. In 1983, 98% of the clones bore a pollen-cone crop compared with 53% in 1986. Lack of fertilization resulting from a limited pollen supply was believed to be the main cause for the lower filled-seed yield in 1986. The effect of wind and controlled (cross-) pollination on filled-seed production was determined for 16 clones in 1983. Seed efficiency after wind and cross-pollination averaged 65 and 69%, respectively. Seed potential averaged 34 and 31 ovules per cone for the wind- and cross-pollinated cones, respectively. Prepollination ovule abortion averaged 12 and 14%, respectively. From anatomical observations, the full-sized but empty seed resulted from lack of fertilization and embryo degeneration. The different factors affecting final filled-seed yield are discussed in terms of their effect on seed production.

Pollination and cone morphology affect cone and seed production in lodgepole pine seed orchards

2005 ◽  
Vol 35 (2) ◽  
pp. 383-400 ◽  
Author(s):  
John N Owens ◽  
Jordan Bennett ◽  
Sylvia L'Hirondelle
Keyword(s):  
British Columbia ◽  
Seed Production ◽  
Reproductive Cycle ◽  
Lodgepole Pine ◽  
Seed Orchards ◽  
Seed Cone ◽  
Orchard Management ◽  
Cone Development ◽  
Pollen Cone ◽  
Developmental Features

We describe the phenology and mechanisms of pollen-cone and seed-cone development in lodgepole pine in the interior of British Columbia and the methods for monitoring cone phenology, pollination, seed production, and causes of seed and cone losses in seed orchards over the 15-month reproductive cycle. Pollination lasted about 2 weeks, between mid-May and mid-June. Pollen shedding and female receptivity showed homogamy, protandry, or protogyny depending on weather, site, and year. Morphological and developmental features explain why pollination as early as stage 3 was most successful and why self-pollination led to a seriously reduced production of filled seed. Early pollination increased the seed potential per cone and consequently the filled seed per cone. Cone drop occurred when less than 80% of ovules were pollinated per cone and was higher in trees from Prince George than those in the Okanagan Valley. Misting of trees and mechanical blowing of pollen in the orchards did not increase filled seed per cone. Clonal effect was the most important factor in all trials and has implications for orchard management.

Seed production and persistence of Carnamah and other early strains of Trifolium subterraneum in the wheatbelt of Western Australia

1967 ◽  
Vol 7 (24) ◽  
pp. 25 ◽  
Author(s):  
GB Taylor ◽  
RC Rossiter
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Western Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Growing Season ◽  
Early Flowering ◽  
The Other ◽  
Factors Affecting ◽  
Seed Yields

Seed production and persistence of the Carnamah, Northam A, Dwalganup, and Geraldton strains of subterranean clover (Trifolium subterraneum L.) were examined in undefoliated swards in the wheatbelt of Western Australia. The early flowering characteristic of Carnamah was not always associated with higher seed yields. Only when there was a well-defined, early finish to the growing season, or when flowering was very much earlier in Carnamah (viz., following an early 'break' to the season), did this strain clearly outyield both Northam A and Geraldton. The seed yield of Dwalganup was generally inferior to that of the other strains. Factors affecting regeneration are discussed. Under low rainfall conditions, poorer germination-regulation of Carnamah, compared with Geraldton and Northam A, would be expected to result in poorer persistence unless offset by higher seed yields in the Carnamah strain.

The pollination mechanism and development after bud burst of cones of Larix laricina

1991 ◽  
Vol 69 (6) ◽  
pp. 1179-1187 ◽  
Author(s):  
G. R. Powell ◽  
Kathleen J. Tosh
Keyword(s):  
Key Words ◽  
Seed Size ◽  
Larix Laricina ◽  
Bud Burst ◽  
Scale Growth ◽  
Pollination Mechanism ◽  
Seed Cone ◽  
Cone Development ◽  
Micropylar Canal ◽  
Pollen Cone

Pollen-cone and seed-cone development, from bud burst to maturity, was investigated on Larix laricina (Du Roi) K. Koch in three young plantations. The pollination mechanism was emphasized. Pollen cones grew rapidly to shed pollen, shrivelled, and remained on the trees for a year or more. Pollen was directed to the ovular regions by the bracts of the seed cones. Pollen adhered among papillae on the larger of two integument extensions. Degeneration of the centre of the papillate integument tip caused a collapse that drew pollen in as the papillate rim grew inward. This ingrowth was joined by that of the smaller integument extension, resulting in a sealed tubular structure that enclosed a dry micropylar canal. Pollen was held by the ingrown plug of degenerated tissue as the nucellus tip expanded into the base of the canal. As this occurred, the ovules, with or without pollination, grew to ultimate seed size, and the initially small ovuliferous scales overgrew the bracts. First bract, then ovuliferous-scale growth was associated with a double-sigmoid form of cone elongation. In mature cones the bracts decreased and the ovuliferous scales (except near the tip) increased in size acropetally. Key words: bract, integument, ovuliferous scale, pollen cone, seed cone, tamarack or eastern larch.

Promotion of flowering in western hemlock by gibberellin A4/7 applied at different stages of bud and shoot development

1989 ◽  
Vol 19 (8) ◽  
pp. 1051-1058 ◽  
Author(s):  
John N. Owens ◽  
Anna M. Colangeli
Keyword(s):  
Effective Treatment ◽  
Shoot Elongation ◽  
Shoot Development ◽  
Western Hemlock ◽  
Bud Burst ◽  
Cone Production ◽  
Seed Cone ◽  
Pollen Cone ◽  
Vegetative Bud

Cone buds were induced on container-grown and field-grown western hemlock (Tsugaheterophylla (Raf.) Sarg.) clones during a 3-year period to study the effects of time and duration of gibberellin A4/7 treatment on cone induction, sexuality of cones, and to relate these results to bud and shoot development. The most effective treatment times preceded anatomical differentiation. The most abundant pollen cones and seed cones were produced when trees were sprayed with gibberellin A4/7 before vegetative bud burst and early shoot elongation. Two to three weekly gibberellin A4/7 applications starting at preswollen and swollen-bud stages were adequate for pollen-cone production. Pollen-cone production decreased when the applications were started at vegetative bud burst or during early shoot elongation. A minimum of three weekly applications were required for seed-cone production, and applications were equally effective when started at preswollen, swollen, and vegetative bud burst stages. Seed-cone production decreased when three weekly applications were started during early shoot elongation; however, this was overcome by increasing the number of applications.

Cone initiation and development before dormancy in yellow cedar (Chamaecyparis nootkatensis)

1974 ◽  
Vol 52 (9) ◽  
pp. 2075-2084 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Mitotic Activity ◽  
Lateral Branch ◽  
Leaf Primordia ◽  
Day Length ◽  
Chamaecyparis Nootkatensis ◽  
Seed Cone ◽  
Cone Development ◽  
Cone Apex ◽  
Lateral Branches ◽  
Pollen Cone

Vegetative shoots initiate leaves and lateral branches continuously from mid-April until the end of September. No buds with bud scales are formed and the vegetative apex is enclosed by leaf primordia at various stages of development. Pollen cones are initiated on proximal vegetative shoots during a 3-week period from mid-June to early in July. Transition to a pollen-cone apex is marked by an increase in mitotic activity in the apex and by the formation of a lateral branch in the axil of one of the last-formed leaf primordia, causing the apex to appear to branch dichotomously. The lateral branch remains at the base of the pollen cone and may resume growth the next year after the pollen cone is shed. Pollen-cone development continues until the end of September. Meiosis occurs during the last 2 weeks of August, and pollen develops during September. Seed cones are initiated on newly formed, distal axillary vegetative shoots during a 3-week period from late June to mid-July. Transition to a seed-cone apex is marked by an increase in mitotic activity followed by bract-scale initiation. Usually three ovules are initiated in the axil of each bract scale. Seed-cone development is complete by early September and the seed cones become dormant. The pattern of reproduction in yellow cedar is compared to other conifers and the possible relationships are discussed between time of cone initiation, sexuality of cones, and day length.

Postdormancy seed-cone development and the pollination mechanism in western hemlock (Tsugaheterophylla)

1989 ◽  
Vol 19 (1) ◽  
pp. 44-53 ◽  
Author(s):  
Anna M. Colangeli ◽  
John N. Owens
Keyword(s):  
Pollen Grains ◽  
Pollen Tubes ◽  
Epicuticular Wax ◽  
Western Hemlock ◽  
Bud Burst ◽  
Pollination Mechanism ◽  
Seed Cone ◽  
Cone Development ◽  
And Function

The development and function of the pollination mechanism is described for hemlock (Tsugaheterophylla (Raf.) Sarg.). Controlled pollinations at various stages following bud burst were used to define the period of maximum receptivity. Western hemlock has a pollination mechanism unlike that observed in other native conifers. The pollen grains were not taken into the micropyles; instead, the roughly sculptured pollen grains adhered to the long epicuticular wax covering the bracts. Seed cones became receptive to pollen soon after the bracts emerged from the bud scales and remained receptive until shortly before cone closure. Several days after the cones fully emerged beyond the bud scales, the ovuliferous scales elongated over the bracts, trapping the pollen between the bracts and scales. Several weeks after pollination, pollen germinated on the bracts and formed long pollen tubes which grew towards and into the micropyles.

A phenological and cytological study of pollen development in western hemlock (Tsuga heterophylla)

1988 ◽  
Vol 66 (5) ◽  
pp. 907-914 ◽  
Author(s):  
Anna M. Colangeli ◽  
John N. Owens
Keyword(s):  
Cell Division ◽  
Pollen Grains ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Bud Burst ◽  
Cone Development ◽  
Tube Cell ◽  
The One ◽  
Pollen Cone ◽  
Stage 1

Pollen-cone development, which was divided into nine phenological stages, was compared with pollen cytology in eight field-grown western hemlock (Tsuga heterophylla (Raf.) Sarg.) clones in 1983 and three container-grown clones in 1984. Phenology proved to be an accurate indicator of cytology, independent of collection dates and rate of development. The breaking of dormancy, the resumption of development, and meiosis occurred during stage 1 (quiescent bud). During stage 2 (swollen pollen-cone bud) the tetrad of microspores separated. The exine wall was completely developed during stage 3 (bud burst). The one-celled microspores began to expand as a result of accumulation of reserves during stage 4, when the pollen cones were one-quarter to one-half emerged through the bud scales. The first cell division occurred during stage 5, when the cones were greater than half emerged. The second and third cell divisions occurred during stage 6, after the cones had completely emerged through the bud scales. The fourth and final cell division, resulting in mature five-celled pollen grains occurred during stage 7 (stalk elongation). Mature pollen consisted of two prothallial cells and a stalk, a body, and a tube cell. Pollen shed occurred at stage 8. The empty cones (stage 9) remained on the trees until the following winter. Some practical implications of relating pollen-cone phenology to cytology are discussed.

Reproductive growth and development in seven provenances of lodgepole pine

1988 ◽  
Vol 18 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Conor O'Reilly ◽  
John N. Owens
Keyword(s):  
Growth And Development ◽  
Reproductive Growth ◽  
Bud Development ◽  
Cone Production ◽  
Growth Increments ◽  
Seed Cone ◽  
Cone Development ◽  
Pollen Release ◽  
The Times ◽  
Pollen Cone

Reproductive growth and development were studied in 1983 in seven provenances of Pinuscontorta Dougl. ssp. latifolia Engelm. growing in a provenance trial near Prince George, B.C. Stages of pollen release and seed-cone receptivity were scored by indices of cone development. Pollen- and seed-cone numbers were estimated and the distribution of seed cones within the upper crown and on annual growth increments of fourth-whorl branches was assessed. Pollen-and seed-cone bud development was followed in sectioned long-shoot buds taken at 2- to 3-week intervals. The times of maximum seed-cone receptivity and pollen release differed slightly among provenances, indicating that there was a high chance of cross-pollination. Differences among provenances in pollen-cone numbers were large, but smaller differences in seed-cone numbers were noted. No mature pollen cones or developing pollen-cone buds were found in the Yukon provenance. Seed-cone production varied with whorl position and was influenced by polycyclic long-shoot development. Potential pollen-cone buds were initiated from May until late June. Pollen cones first differentiated in early to mid July in all provenances. Potential seed-cone apices were noted from mid-June to late July and differentiation occurred in mid-July to early August, depending on provenance. Seed-cone bud development began first in the northern provenances.

Bud development in western hemlock. II. Initiation and early development of pollen cones and seed cones

1974 ◽  
Vol 52 (2) ◽  
pp. 283-294 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Tsuga Heterophylla ◽  
Day Length ◽  
Western Hemlock ◽  
Reproductive State ◽  
Bud Development ◽  
Seed Cone ◽  
Cone Apex ◽  
Lateral Branches ◽  
Mother Cells ◽  
Pollen Cone

Seed cones in Tsuga heterophylla (Raf.) Sarg. are found at the tips of distal lateral branches and form as a result of the transition of a previously vegetative apex. Pollen cones may be formed similarly and are then found at the tips of less-vigorous proximal branches but more commonly they develop from newly initiated axillary buds on short proximal shoots. In all cases, apices undergo transition to the reproductive state after a period of bud-scale initiation. Some apices initiate many bud scales, then either initiate leaves or undergo transition to a seed-cone apex in July. Other apices initiate fewer bud scales, then late in June undergo transition to a pollen-cone apex. Transition to a reproductive apex is marked by an increase in mitotic activity and apical size and loss of the vegetative pattern of zonation. Zonation reappears during the slower period of late bract and microsporophyll initiation but is not as prominent as it was in vegetative apices. In seed-cone buds, all bracts, ovuliferous scales, and megaspore mother cells are formed before dormancy. In pollen-cone buds all microsporophylls and microsporangia are initiated before dormancy and pollen mother cells begin meiosis and remain in the diffuse diplotene stage during dormancy. Pollen- and seed-cone buds become dormant in December. The time of cone initiation and sexuality of cones may be influenced by day length. The pattern of reproduction in western hemlock is compared in some respects with that of other conifers.

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