Further observations on the pollination mechanism and seed production of Douglas-fir

1982 ◽  
Vol 12 (2) ◽  
pp. 431-434 ◽  
Author(s):  
John N. Owens ◽  
Sheila J. Simpson
Keyword(s):  
Seed Production ◽  
Pollen Grains ◽  
Germination Percentage ◽  
Douglas Fir ◽  
Pollination Mechanism ◽  
Supplemental Pollination

The pollination mechanism of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) was studied. Pollen stained five different colors and applied to the same conelets at five different times showed that the pollen applied on the 1st and 3rd days after conelets became receptive was taken into the micropyle in significantly greater quantities than pollen applied at later dates. A second supplemental pollination did not increase the seed efficiency for individual cones. Seeds produced when an average of less than 1.2 pollen grains were taken into the micropyle had essentially the same germination percentage and proportion of abnormal germinants as seeds resulting when an average of 3.4 or more pollen grains were taken into the micropyle.

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 Effect of High Concentrations of Ethylene on Seed Germination of Douglas Fir (Pseudotsugamenziesii (Mirb.) Franco)

1975 ◽  
Vol 5 (3) ◽  
pp. 419-423 ◽  
Author(s):  
Carey Borno ◽  
Iain E. P. Taylor
Keyword(s):  
Seed Germination ◽  
Germination Rate ◽  
Inhibitory Effect ◽  
Germination Percentage ◽  
Douglas Fir ◽  
Control Treatment ◽  
Continuous Exposure ◽  
Short Term ◽  
Short Term Exposure ◽  
High Concentrations

Stratified, imbibed Douglas fir (Pseudotsugamenziesii (Mirb.) Franco) seeds were exposed to 100% ethylene for times between 0 and 366 h. Germination rate and germination percentage were increased by treatments up to 48 h. The 12-h treatment gave largest stimulation; 30% enhancement of final germination percentage over control. Treatment for 96 h caused increased germination rate for the first 5 days but reduced the germination percentage. Germinants were subject to continuous exposure to atmospheres containing 0.1 – 200 000 ppm ethylene in air, but it did not stimulate growth, and the gas was inhibitory above 100 ppm. Although some effects of high concentrations of ethylene may have been due to the lowering of oxygen supplies, this alone was insufficient to account for the full inhibitory effect. The mechanism of stimulation by short-term exposure to ethylene is discussed.

SPONTANEOUS SELF-FERTILIZATION IN RELATION TO SEED PRODUCTION IN SWEET CLOVER (MELILOTUS)

1931 ◽  
Vol 5 (6) ◽  
pp. 660-664 ◽  
Author(s):  
L. E. Kirk ◽  
T. M. Stevenson
Keyword(s):  
Seed Production ◽  
Pollen Grains ◽  
Sweet Clover ◽  
Flower Structure ◽  
Melilotus Officinalis ◽  
Stigmatic Surface ◽  
Melilotus Alba ◽  
Self Fertilization ◽  
Determining Factor ◽  
Selection Of

The chief determining factor in spontaneous self-fertilization in white sweet clover (Melilotus alba) appears to be the distribution of pollen within the unopened flowers. This in turn depends on (1) length of stamens, (2) length of style, (3) amount of pollen, and (4) size of cavity within the upper part of the keel. When the flower structure and quantity of pollen is such as to insure the deposition of pollen grains on the stigma before the blossom is likely to be disturbed by insects, the plant will be normally self-fertilized. In the yellow flowered species of sweet clover (Melilotus officinalis) spontaneous self-fertilization is effectively prevented, except in certain varieties, by a characteristic of the stigma which makes it unreceptive. Scarification of the stigmatic surface appears to be necessary before fertilization can take place. Variation occurs also, as in M. alba, in the length of stamens and style, size of keel cavity, and the amount of pollen.There is a high correlation in M. alba between the percentage of flowers which are naturally self-pollinated and the percentage of flowers which produce pods when the plants are caged to exclude insects. Selection of plants which are normally self-fertilized can be made by examining the early flowers, thus obviating the necessity of bagging or caging plants which do not possess this character.A strain of M. alba which is normally self-fertilized was found to produce almost twice as much seed as another strain which is normally cross-pollinated under comparable conditions in the field.

Clonal variation in pollen-related characteristics of Douglas-fir

1982 ◽  
Vol 12 (2) ◽  
pp. 403-408 ◽  
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.

CONSUMPTION OF VARIOUS DOUGLAS-FIR CONE STRUCTURES BY BARBARA COLFAXIANA (LEPIDOPTERA: OLETHREUTIDAE)

1977 ◽  
Vol 109 (9) ◽  
pp. 1293-1294
Author(s):  
T. Evan Nebeker
Keyword(s):  
Energy Transfer ◽  
Seed Production ◽  
Energy Budget ◽  
Forest Ecosystem ◽  
Larval Stage ◽  
Douglas Fir ◽  
National Forest ◽  
Larval Instars ◽  
Production Area

During 1971 a study was conducted to determine the amount of the various Douglasfir cone structures (bracts, scales, and seeds) consumed by the Douglas-fir cone moth, Barbara colfaxiana (Kft.), in the Buckhead Seed Production Area, Willamette National Forest, Oregon. It was not the intent of this study to develop a complete energy budget for B. colfaxiana, but rather to determine the number of calories consumed, on the average, by an individual during the larval stage. The behavior of the various larval instars has been discussed by Radcliffe (1952), Keen (1958), Hedlin (1960), and Nebeker (1977). The calorie was selected as the unit of measure due to its usefulness in modeling energy transfer from one component to another in the forest ecosystem.

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.

Seed production and its components in bred populations and cultivars of winter-green Setaria sphacelata at two levels of applied nitrogen fertiliser

1994 ◽  
Vol 34 (2) ◽  
pp. 153 ◽  
Author(s):  
JB Hacker
Keyword(s):  
Seed Production ◽  
Germination Percentage ◽  
Nitrogen Fertiliser ◽  
Setaria Sphacelata ◽  
Low Levels ◽  
Tiller Density ◽  
Seed Yields ◽  
Positive Effect ◽  
Inflorescence Length ◽  
Applied Nitrogen

Seed production of 2 experimental winter- green varieties of Setaria sphacelata, EHB (released as cv. Solander) and EHC, was compared with the winter-green cv. Narok in a split-plot experiment with 2 levels of applied nitrogen (N) fertiliser. The experiment continued for 3 years (6 harvests), and 3 subharvests at 1-2-week intervals were taken at each major harvest to allow for possible phenological differences between varieties. Total numbers of basal tillers, and of basal and aerial tillers with inflorescences, were counted at each harvest. Ripe and shedding inflorescences were counted, dried, and threshed by hand, and the seed was sieved and aspirated. The aspirated seed was stored for 6 months, the percentage of spikelets containing caryopses was evaluated, and samples were germinated in petri dishes. Aspirated seed yields of Solander were mostly 50-100% higher than those of Narok, except where yields were generally low, associated with low levels of applied N, and in later harvests of the experiment. All 3 entries showed a progressive decrease in seed production over time, and no consistent phenological difference was apparent. The improved seed production of Solander was associated with a markedly higher tiller fertility, lower basal tiller density, and slightly longer inflorescences. Germination percentage of Solander was consistently lower than that of Narok, and it was postulated that this was due to a higher level of seed dormancy. Nitrogen fertiliser had a marked positive effect on seed production, inflorescence numbers, tiller fertility, basal tiller density, and inflorescence length in all populations.

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