The pollination mechanism of Sitka spruce (Picea sitchensis)

1984 ◽  
Vol 62 (6) ◽  
pp. 1136-1148 ◽  
Author(s):  
John N. Owens ◽  
Margaret D. Blake
Keyword(s):  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Optimal Time ◽  
Secretory Cells ◽  
Drop Formation ◽  
Winter Dormancy ◽  
Pollination Mechanism ◽  
Seed Cone ◽  
Pollination Drop ◽  
And Function

The development and function of the pollination mechanism and the optimal time for pollination are described for Sitka spruce (Picea sitchensis (Bong.) Carr.). After winter dormancy, the rudimentary integument overgrew the nucellus and formed two long micropylar arms. Soon after seed-cone buds burst, the epidermal cells on the micropylar arms secreted mucilage droplets to which pollen adhered. The ultrastructure of mucilage droplet secretion is described. After 6–8 days a pollination drop formed from the nucellus. This filled the space between the micropylar arms and picked up any pollen which adhered to the arms or landed on the pollination drop. The pollination drop was then withdrawn carrying pollen into the micropyle. The secretory cells on the micropylar arms then autolyzed and a large mucilage plug sealed the micropyle and filled the space between the withered micropylar arms. Conelets closed and became pendant. Pollen germinated and pollen tubes formed about 2 weeks after pollination ended. Conelets enclosed in pollination bags were open and receptive for about 10 days, but the optimal time for pollination was 6 to 8 days after cone buds burst. This coincided with the time of pollination-drop formation.

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.

The pollination mechanism and the optimal time of pollination in Douglas-fir (Pseudotsugamenziesii)

1981 ◽  
Vol 11 (1) ◽  
pp. 36-50 ◽  
Author(s):  
John N. Owens ◽  
Sheila J. Simpson ◽  
Marje Molder
Keyword(s):  
Electron Microscopy ◽  
Seed Set ◽  
Pollen Grains ◽  
Douglas Fir ◽  
Optimal Time ◽  
Pollination Mechanism ◽  
Seed Cone ◽  
Poor Seed ◽  
Micropylar Canal ◽  
Scanning Electron

The development of the pollination mechanism and the engulfment of pollen by the stigmatic tip is described for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) based on scanning electron microscopy. This information is used to determine and explain the optimal time of pollination and amount of pollen needed for maximum seed set. After dormancy the integument tip of the ovule developed into an unequally two-lobed stigmatic tip covered with long unicellular hairs. Most ovules had fully developed stigmatic tips when the seed cone emerged from the bud scales in early April. The conelets remained open and the stigmatic tip was most receptive for at least 4 days. Pollen freely sifted down between the bracts and ovuliferous scales and adhered to the stigmatic hairs. Six days after the conelets became receptive, stigmatic hairs around the micropyle began to collapse and were ungulfed with the entangled pollen into the micropyle. Also, ovuliferous scales began to thicken, restricting movement of pollen to the stigmatic tips. By 8–10 days after conelets became receptive, the stigmatic tips were completely engulfed, the ovuliferous scales had thickened enough to close the conelet, and the conelet had begun to bend down.Maximum seed set occurred when (1) cones were pollinated within 4 days after seed-cone buds had emerged half of the way out of their bud scales; (2) a minimum of 0.2 g of pollen was used per pollination bag; (3) a minimum of 11 pollen grains adhered to each stigmatic tip; and (4) at least 3 pollen grains were taken into each micropylar canal. The engulfing process occurred at the same rate and in the same manner regardless of whether living or heat-killed pollen was present or absent on the stigmatic surface. Poor seed set as it related to the pollination mechanism is discussed.

How the pollination mechanism and prezygotic and postzygotic events affect seed production in Larixoccidentalis

1994 ◽  
Vol 24 (5) ◽  
pp. 917-927 ◽  
Author(s):  
John N. Owens ◽  
Sheila J. Morris ◽  
Glenda L. Catalano
Keyword(s):  
Seed Production ◽  
Ultrastructural Changes ◽  
Optimal Time ◽  
Cell Cytoplasm ◽  
Pollination Mechanism ◽  
X Ray ◽  
Pollination Success ◽  
Pollen Hydration ◽  
Pollination Drop ◽  
Supplemental Pollination

The pollination mechanism of western larch (Larixoccidentalis Nutt.) is described in relation to the optimal time of pollination. Five stages of conelet receptivity were recognized and stages two to four had the greatest pollination success. Four categories of seed were recognized by X-ray and dissection of seeds from mature cones. The causes of degenerated, empty, and rudimentary seeds are discussed and recommendations are made for increased seed production through supplemental pollination. Light microscope and ultrastructural observations were made of the pollination mechanism and of pollen from 0 to 72 h after pollination, during pollen engulfment, during shedding of the exine, and during penetration of the nucellus. Pollen attachment to stigmatic hairs and pollen engulfment are described. Pollen hydration and ultrastructural changes began about 72 h after pollination. The exine was shed but the pollen remained just inside the sealed micropyle for 5–6 weeks. A pollination drop secreted from the nucellus then carried the pollen to the nucellus. There a pollen tube formed and penetrated the nucellus. Two male nuclei formed in a common body-cell cytoplasm when the pollen tubes reached the archegonia.

The pollination mechanism of Engelmann spruce (Picea engelmannii)

1987 ◽  
Vol 65 (7) ◽  
pp. 1439-1450 ◽  
Author(s):  
John N. Owens ◽  
Sheila J. Simpson ◽  
Guy E. Caron
Keyword(s):  
Seed Set ◽  
Picea Engelmannii ◽  
Diurnal Fluctuation ◽  
Secretory Cells ◽  
Controlled Environment ◽  
High Humidity ◽  
Natural Conditions ◽  
Pollination Mechanism ◽  
Engelmann Spruce ◽  
Pollination Drop

The pollination mechanism of Picea engelmannii (Parry) was studied on small potted scions under natural conditions and in controlled environment chambers. Six stages of conelet development were recognized and related to pollen receptivity. Cone-lets appeared receptive for about 2 weeks but were actually receptive for only about 1 week. Secretory droplets appearing on the micropylar arms collected pollen for several days before pollination drops formed. Pollination drops formed acropetally in the conelet and only once from each ovule. Pollination caused rapid recession of the pollination drop, whereas the drop remained for several days on unpollinated ovules. There was some decrease in size of pollination drops during midday and reemergence the following night. Pollination drops were secreted by the nucellar tip in a manner similar to nectaries. Secretory cells collapsed following secretion. The drop contained 4.3% glucose and 3.8% fructose but no sucrose. High humidity increased the longevity and decreased the diurnal fluctuation in size of pollination drops. Conelets from trees with low leaf water potential developed more slowly and produced smaller and more viscous pollination drops. Cones averaged 103 ovuliferous scales, 90% of which were fertile. However, usually less than 50% of the potential seed set was achieved. One of the major causes for low seed set is inadequate pollination. A better understanding of the pollination mechanism and the receptive period may improve seed efficiency in controlled and supplemental mass pollinations.

The pollination mechanism in yellow cypress (Chamaecyparisnootkatensis)

1980 ◽  
Vol 10 (4) ◽  
pp. 564-572 ◽  
Author(s):  
John N. Owens ◽  
Sheila J. Simpson ◽  
Marje Molder
Keyword(s):  
Lipid Droplets ◽  
Pollen Grains ◽  
Water Droplets ◽  
Pollination Mechanism ◽  
Seed Cone ◽  
Pollination Drop ◽  
Micropylar Canal ◽  
The One ◽  
Cuticular Surface

Mature, dry, one-celled pollen was formed before pollen cones became dormant in the fall. Pollen averaged 27 μm in diameter, was irregular in shape, nonsaccate, and the surface was reticulate to tegillate-baculate and irregularly covered with orbicules. The pollen contained several large lipid droplets and no starch. No changes occurred in pollen during dormancy and pollen was shed at the one- or two-celled stage during the last half of March.All ovules were initiated and became flask shaped before seed-cone dormancy. No changes occurred in ovules during dormancy. Seed cones ended dormancy in early March, enlarged and opened, exposing the ovules. A pollination drop was produced by a breakdown of cells at the tip of the nucellus. A large pollination drop was exuded from each ovule in a cone but exudation did not occur at the same time in all ovules. Each ovule exuded and withdrew a pollination drop two to four times before the pollination drop was permanently withdrawn. Each ovule was receptive for a few days and each cone was receptive for about 1 week. The pollination drops were withdrawn in the presence or absence of pollen but were withdrawn more rapidly after pollen entered the pollination drop. The cuticular surface of the bract-scales prevented wetting of the surface and caused the beading of water droplets, which in turn could carry pollen to the micropyle. Pollen grains entering a pollination drop were withdrawn inside the drop into the micropyle. Cells lining the micropylar canal enlarged and sealed the canal while bract-scales enlarged and buried the ovules within the cone.

The pollination mechanism of Abies amabilis

2004 ◽  
Vol 34 (5) ◽  
pp. 1071-1080 ◽  
Author(s):  
Luke M Chandler ◽  
John N Owens
Keyword(s):  
Electron Microscopy ◽  
Epicuticular Wax ◽  
Pollination Mechanism ◽  
Abies Amabilis ◽  
Cone Axis ◽  
Inner Surface ◽  
Pollination Drop ◽  
And Function ◽  
Scale Surface ◽  
Scanning Electron

The development and function of the pollination mechanism were studied in Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes growing in clonal seed orchards. Two adaxial ovules developed on each scale after dormancy and each ovule formed a funnel-like integument tip with a nucellus at the base of the shallow funnel. At receptivity, the seed cones were erect and the ovules inverted. No pollination drop was observed in fresh specimens but lipid microdrops were secreted on the rim and inner surface of the funnel. Water applied as spray beaded on all cone surfaces except where microdrops were present. Surfaces of the cone were observed using scanning electron microscopy to determine the presence and ultrastructure of the waxy cuticle. All surfaces that were not wettable with water were covered with epicuticular wax. Pollen did not adhere firmly to cone surfaces having epicuticular wax but adhered to the microdrops on the funnel. Drops of water picked up pollen as they moved over the waxy surfaces toward the cone axis. There, the inverted ovules were arranged in a tight helix around the cone axis. Beads of water, often containing pollen, settled on the scale surface just below the funnels and then touched and wetted the inside of the funnels, forming a column of water from the scale surface below to the funnel above. The saccate, buoyant pollen then floated up and into the funnel. Experiments were done to determine the effect of pollen application on pollen uptake into the ovule: without water, with water applied before or after pollen was applied, or as a pollen–water mix. Results support the hypothesis that A. amabilis, and likely other Abies species, lacks a conspicuous pollination drop and water as rain or dew substitutes for a pollination drop.

Pollen scavenging and rain involvement in the pollination mechanism of interior spruce

1996 ◽  
Vol 74 (1) ◽  
pp. 115-124 ◽  
Author(s):  
C. John Runions ◽  
John N. Owens
Keyword(s):  
Picea Glauca ◽  
Selective Pressure ◽  
Seed Orchard ◽  
Picea Engelmannii ◽  
Pollination Efficiency ◽  
Pollination Mechanism ◽  
Pollination Mechanisms ◽  
Seed Cone ◽  
Interior Spruce ◽  
Pollination Drop

Pollination drops are secreted from the ovules of interior spruce (Picea glauca or Picea engelmannii and their hybrid) as seed cones begin to close at the end of the pollination period. Secreted pollination drops persist within spaces surrounding the micropylar opening in closed seed cones. Saccate pollen floats into the micropyle within the pollination drop. Pollination drops become voluminous enough, within the enclosed spaces, to scavenge pollen adhering to the micropylar arms and other surfaces in proximity with the micropyle. Scavenging of pollen from cone surfaces adjacent to the integuments is sometimes facilitated by rainwater that can float pollen into the opening of the micropyle before cone closure and pollination drop secretion. In practice, periodic, light misting of seed orchard trees during seed cone receptivity might increase pollination efficiency by mimicking rainwater involvement in the pollination mechanism. Rainwater involvement in pollination of some modern conifers may reflect a similar situation in the pollination mechanisms of ancestral conifers. Environments with limited rainfall combined with the requirement for moisture in the pollination mechanism may have provided the selective pressure for evolution of the pollination drop. Keywords: pollination drop, Picea, conifer, sacci.

Predicting the longitudinal modulus of elasticity of Sitka spruce from cellulose orientation and abundance

Holzforschung ◽  
2010 ◽  
Vol 64 (4) ◽  
Author(s):  
J. Paul McLean ◽  
Robert Evans ◽  
John R. Moore
Keyword(s):  
Bulk Density ◽  
Modulus Of Elasticity ◽  
Microfibril Angle ◽  
Sitka Spruce ◽  
Picea Sitchensis ◽  
Model Parameters ◽  
Bending Tests ◽  
Wood Stiffness ◽  
Using Data ◽  
Longitudinal Modulus

Abstract Sitka spruce (Picea sitchensis) is the most widely planted commercial tree species in the United Kingdom and Ireland. Because of the increasing use of this species for construction, the ability to predict wood stiffness is becoming more important. In this paper, a number of models are developed using data on cellulose abundance and orientation obtained from the SilviScan-3 system to predict the longitudinal modulus of elasticity (MOE) of small defect-free specimens. Longitudinal MOE was obtained from both bending tests and a sonic resonance technique. Overall, stronger relationships were found between the various measures of cellulose abundance and orientation and the dynamic MOE obtained from the sonic resonance measurements, rather than with the static MOE obtained from bending tests. There was only a moderate relationship between wood bulk density and dynamic MOE (R2=0.423), but this relationship was improved when density was divided by microfibril angle (R2=0.760). The best model for predicting both static and dynamic MOE involved the product of bulk density and the coefficient of variation in the azimuthal intensity profile (R2=0.725 and 0.862, respectively). The model parameters obtained for Sitka spruce differed from those obtained in earlier studies on Pinus radiata and Eucalyptus delegatensis, indicating that the model might require recalibration before it can be applied to different species.

Photosynthesis in Sitka Spruce (Picea sitchensis (Bong,) Carr.): VII. Measurements of Stomatal Conductance and 14 CO 2 Uptake in a Forest Canopy

1976 ◽  
Vol 13 (2) ◽  
pp. 623 ◽  
Author(s):  
W. R. Watts ◽  
R. E. Neilson ◽  
P. G. Jarvis
Keyword(s):  
Stomatal Conductance ◽  
Forest Canopy ◽  
Sitka Spruce ◽  
Picea Sitchensis
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