Compound pollen cone in a Paleozoic conifer

Two experiments in black spruce (Picea mariana (Mill.) BSP) seedling seed orchards were established to determine if a stem injection of paclobutrazol (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl) could be used as an adjunct treatment to increase the efficacy of stem injections of gibberellins A4 and A7 (GA4/7). Trees received a single injection of GA4/7 and (or) paclobutrazol shortly after vegetative bud burst. There was a dose-dependent but nonlinear increase in the production of cones of both sexes in response to stem injections of either GA4/7 or paclobutrazol. The optimum rate of GA4/7 for stimulating pollen-cone production was 3.3 mg, whereas the most seed cones were induced on trees receiving 11 mg. The sex ratio (number of seed cones/number of pollen cones) increased with the rate of GA4/7 applied. Injecting paclobutrazol also promoted cones of both sexes equally, resulting in sex ratios comparable with that of the control trees. Treatments did not affect the total numbers of buds (vegetative, latent, and cone) produced. Seed- and pollen-cone buds occurred in positions that would have otherwise developed vegetatively and become latent, respectively. The mechanisms whereby paclobutrazol could affect flowering in black spruce are discussed. The use of paclobutrazol as an adjunct to GA4/7 treatments in black spruce seedling seed orchards appears effective, practical, and safe.

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Clonal variation in pollen-related characteristics of Douglas-fir

Canadian Journal of Forest Research ◽

10.1139/x82-057 ◽

1982 ◽

Vol 12 (2) ◽

pp. 403-408 ◽

Cited By ~ 6

Author(s):

W. T. Adams

Keyword(s):

Genetic Variation ◽

Pollen Grains ◽

Seed Orchard ◽

Douglas Fir ◽

Clonal Variation ◽

Pollen Production ◽

The Mean ◽

Pollen Cone ◽

Grain Diameter

The mean number of pollen grains produced per pollen cone (P) ranged from 37 310 to 62 960 ([Formula: see text], SE = 1584) among eight seed-orchard clones of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and correlated significantly (r = 0.87, p < 0.05) with the mean number of microsporophylls per cone but not significantly with pollen cone length. The number of pollen grains per milligram (G) also differed among clones (range 2323–3112; [Formula: see text], SE = 32) and correlated significantly and negatively (r = −0.86) with grain diameter. Although this study provides evidence for genetic variation in both P and G, the differences were relatively small. Adjusting pollen-cone counts for P would add little, if any, precision to estimates of pollen production in seed-orchard clones. If balanced clonal representation in pollen mixes is desired, equal weights of pollen would probably suffice for most breeding applications.

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

Canadian Journal of Botany ◽

10.1139/b91-151 ◽

1991 ◽

Vol 69 (6) ◽

pp. 1179-1187 ◽

Cited By ~ 5

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.

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

Canadian Journal of Forest Research ◽

10.1139/x89-160 ◽

1989 ◽

Vol 19 (8) ◽

pp. 1051-1058 ◽

Cited By ~ 4

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.

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Bud development in mountain hemlock (Tsuga mertensiana). II. Cone-bud differentiation and predormancy development

Canadian Journal of Botany ◽

10.1139/b84-072 ◽

1984 ◽

Vol 62 (3) ◽

pp. 484-494 ◽

Cited By ~ 4

Author(s):

John N. Owens

Keyword(s):

Shoot Elongation ◽

Bud Development ◽

Seed Cone ◽

Cone Apex ◽

Tsuga Mertensiana ◽

Lateral Branches ◽

Mother Cells ◽

Pollen Cone ◽

Bud Initiation ◽

Vegetative Bud

Seed cones of Tsuga mertensiana (Bong) Carr. occur terminally on distal lateral branches and form from the differentiation of a terminal, previously vegetative apex, into a seed-cone apex. Pollen cones commonly occur on lateral branches and form from the differentiation of an undetermined axillary apex about 6 weeks after axillary bud initiation. Pollen cones also occasionally occur terminally. All cone buds began differentiation in late July after bud-scale initiation was complete and at about the end of lateral shoot elongation. Seed-cone buds initiated bracts and ovuliferous scales, but not ovules, before they became dormant at the end of October. Pollen-cone buds initiated all microsporophylls by early September. Microsporangia containing microspore mother cells differentiated before pollen-cone buds became dormant in mid-October. The time of cone-bud differentiation is related to vegetative bud and shoot development. The time and method of cone-bud differentiation is discussed in relation to T. heterophylla and other conifers having similar bud development.

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Effects of girdling and gibberellin A4/7 on flowering of European and Japanese larch grafts in an outdoor clone bank

Canadian Journal of Forest Research ◽

10.1139/x26-039 ◽

1996 ◽

Vol 26 (3) ◽

pp. 355-359 ◽

Cited By ~ 7

Author(s):

J.J. Philipson

Keyword(s):

Effective Treatment ◽

Japanese Larch ◽

Main Stem ◽

European Larch ◽

The Mean ◽

Pollen Cone ◽

Stem Girdling

Field-grown European larch (Larixdecidua Mill.) and Japanese larch (Larixkaempferi (Lamb.) Carr.) grafts were treated with main-stem girdling applied with or without injection of gibberellin A4/7 (GA4/7). The level of female coning was low in the untreated trees and was significantly increased by girdling; the mean number of seed cones per tree, on trees receiving girdling alone, was 71 for the European larch and 50 for the Japanese larch. There was considerable male flowering on the untreated trees, (701 and 1208 cones per tree on the European and Japanese larch, respectively), and on trees receiving girdling alone there were 1356 pollen cones per tree on the European larch, and 2035 on the Japanese larch, representing increases of 94 and 68%, respectively, compared with the untreated trees. The overall girdling effect on male flowering, however, was not statistically significant for either species. GA4/7 application produced no significant increases in coning, and in fact fewer pollen cones were observed on GA4/7-treated grafts than on grafts without GA4/7. Between 6 and 12% of the pollen-cone buds on untreated trees did not flush successfully, and the GA4/7 application significantly increased this proportion of unflushed buds. Girdling is an easy and effective treatment to increase female coning of European and Japanese larch and may also result in increases in pollen cones; thus, it would be a useful treatment to assist in the breeding of these species and the production of their hybrid (Larix ×eurolepis A. Henry).

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

Canadian Journal of Botany ◽

10.1139/b74-266 ◽

1974 ◽

Vol 52 (9) ◽

pp. 2075-2084 ◽

Cited By ~ 10

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.

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Gibberellin A4/7 enhanced flowering in Pinuscaribaea var. hondurensis

Canadian Journal of Forest Research ◽

10.1139/x91-111 ◽

1991 ◽

Vol 21 (6) ◽

pp. 788-793 ◽

Cited By ~ 6

Author(s):

Derek L. S. Harrison ◽

Mike U. Slee

Keyword(s):

Single Treatment ◽

Bud Development ◽

Cone Production ◽

Seed Cone ◽

Pollen Cone ◽

Sexually Mature

Gibberellin A4/7 was applied to field-grown grafts of sexually mature poor and good flowering clones of Pinuscaribaea Morelet var. hondurensis. Barr. & Golf. Continuous applications of gibberellin A4/7 over a 6-week period significantly enhanced seed-cone production in poor flowering clones but had no effect on good flowering clones. Poor flowering clones also showed slight decreases in pollen-cone production with gibberellin A4/7, while clones that normally flowered well did not. Gibberellin A4/7 increased final shoot lengths in the lower (male) and upper (female) crown region of both poor and good flowering clones. A series of timed gibberellin A4/7 applications suggested that a single treatment near the onset of reproductive bud development may be used to enhance seed-cone production.

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