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.

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 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.

Pollination mechanism of seed orchard interior spruce

1995 ◽  
Vol 25 (9) ◽  
pp. 1434-1444 ◽  
Author(s):  
C. John Runions ◽  
Glenda L. Catalano ◽  
John N. Owens
Keyword(s):  
Temporal Correlation ◽  
Seed Orchard ◽  
Pollination Mechanism ◽  
Pollination Success ◽  
Engelmann Spruce ◽  
Interior Spruce ◽  
Pollination Drop ◽  
Cone Development ◽  
Dry Conditions ◽  
Natural Range

The pollination mechanism of interior spruce (white spruce, Piceaglauca (Moench) Voss, or Engelmann spruce, Piceaengelmannii Parry, and their hybrid) trees growing in a seed orchard was studied. Seed orchards are established in areas that are warmer and drier than the parent tree natural range. Hot, dry conditions during the pollination period adversely affected secretion of the pollination drop in unbagged seed cones as compared with bagged cones on the same tree. Unbagged cones remained open and apparently receptive for pollination for 5.3 ± 1.6 days (100 ± 31 h at >10°C), but pollination drops did not appear during this period. Pollination drops were secreted as cones began to close. The temporal correlation observed between cone closure and pollination drop secretion occurred as well in the higher relative humidity environment within pollination bags. Pollination drops in unbagged cones were smaller and did not persist as long as those in bagged cones. The micropylar arms, which capture pollen prior to pollination drop secretion, withered completely in unbagged cones before pollination drops were observed. Some withering of micropylar arms during cone receptivity is natural but complete withering means that the arms can not function in pollen capture throughout the period during which cones remain open. For this reason, supplemental mass pollination is best carried out early during the receptive period for trees growing in hot, dry environments. Overhead misting, used periodically during the receptive period to cool orchard trees, might slow seed-cone development and reduce micropylar arm withering, thereby increasing pollination success after supplemental mass pollination.

scholarly journals Ultrastructural Changes in the Pancreata of Selenium-Vitamin E-Deficient Chicks

1977 ◽  
Vol 14 (6) ◽  
pp. 629-642 ◽  
Author(s):  
A. H. Rebar ◽  
J. F. Van Vleet
Keyword(s):  
Endoplasmic Reticulum ◽  
Vitamin E ◽  
Acinar Cell ◽  
Interstitial Fibrosis ◽  
Ultrastructural Changes ◽  
Zymogen Granules ◽  
Cell Cytoplasm ◽  
Torula Yeast ◽  
Cell Changes ◽  
Ductular Proliferation

Three hundred and seventy 1-day-old male, white Leghorn chicks were divided into seven groups and fed a series of semipurified torula yeast diets either deficient in or supplemented with selenium and vitamin E. Chicks in each group were necropsied sequentially and the pancreata examined by light microscopy. Selected pancreata of selenium deficient chicks in various stages of the deficiency disease were examined by electron microscopy. Supplements of either selenium (0.2 mg/kg) or vitamin E (100 IU/kg diet) resulted in protection against pancreatic lesions. Changes in pancreata of selenium deficient chicks progressed from cytoplasmic vacuolation of acinar cell cytoplasm to focal disseminated acinar necrosis. There was ductular proliferation and interstitial fibrosis in advanced lesions. Acini around islets were less frequently affected than acini further away. Ultrastructurally, the mildest lesions were focal dilation of the endoplasmic reticulum and autophagic vacuoles in acinar cell cytoplasm. Necrotic areas contained both membranous and granular debris and fragments of intact endoplasmic reticulum. In fibrotic pancreata the main acinar cell changes were uniform dilation of endoplasmic reticulum and reduction in number of zymogen granules.

scholarly journals Floral Biology and Seed Production in Cultivated North American Ginseng (Panax quinquefolius)

2000 ◽  
Vol 125 (5) ◽  
pp. 567-575 ◽  
Author(s):  
Cayetana Schluter ◽  
Zamir K. Punja
Keyword(s):  
Seed Production ◽  
North American ◽  
Age Groups ◽  
Morphological Characteristics ◽  
Floral Biology ◽  
American Ginseng ◽  
Panax Quinquefolius ◽  
Flowering Period ◽  
Pollination Success ◽  
Pollen Release

Morphological characteristics of flowers, duration of flowering, degree of self-pollination, and extent of berry and seed production in North American ginseng (Panax quinquefolius L.) were studied under controlled environmental conditions as well as under field conditions. A comparison was also made between plants of 3 and 4 years of age at two field locations. The duration of flowering was ≈4 weeks and was similar in plants of both age groups grown in the two environments; however, 4-year-old plants produced an average of 40% more flowers (≈100 per plant in total) compared to 3-year-old plants. Flowers were comprised of five greenish-colored petals, five stamens, and an inferior ovary consisting of predominantly two fused carpels and stigmatic lobes. Anthers dehisced in staggered succession within individual flowers, and flowering began with the outermost edge of the umbel and proceeded inwards. At any given time during the 4-week flowering period, ≈10% of the flowers in an umbel had recently opened and were producing pollen. Stigma receptivity was associated with separation of the stigmatic lobes; this occurred at some time after pollen release. Growth of pollen tubes through the style in naturally pollinated flowers was most evident when the stigmatic lobes had separated. The proportion of flowers that developed into mature berries (pollination success rate) was in the range of 41% to 68% for both 3-year-old and 4-year-old plants. However, when the inflorescence was bagged during the flowering period, berry formation was increased by 13% to 21% in 4-year-old plants, depending on location. A majority of the berries (92% to 99%) contained one or two seeds in an almost equal frequency, with the remaining berries containing three seeds. In 4-year-old plants, the frequency of two-seeded berries was increased by ≈13% by bagging the inflorescence. These observations indicate that P. quinquefolius is highly self-fertile and that several physiological and environmental factors can affect seed production.

Sexual reproduction in western red cedar (Thuja plicata)

1980 ◽  
Vol 58 (12) ◽  
pp. 1376-1393 ◽  
Author(s):  
John N. Owens ◽  
M. Molder
Keyword(s):  
Sexual Reproduction ◽  
Seed Production ◽  
Low Temperatures ◽  
Female Gametophyte ◽  
Seed Set ◽  
Thuja Plicata ◽  
Insect Damage ◽  
Red Cedar ◽  
Pollination Drop ◽  
Micropylar Canal

Pollen cones and seed cones ended dormancy in mid-February, microsporogenesis occurred in late February, and pollination occurred for about 1 week in early March. Pollen was shed at the two-celled stage. Pollination drops were exuded from only a few ovules at one time. Pollen contacting the pollination drop was rapidly taken in. The pollination drop was withdrawn into the micropyle which was later sealed by enlargement of cells lining the micropylar canal. Megasporogenesis occurred in late February but female gametophytes did not mature and fertilization did not occur until late May. An archegonial complex formed containing seven to nine archegonia, of which several usually were fertilized. Proembryo development varied depending upon the size and shape of the archegonia. Usually, a 12-celled, three-tiered proembryo formed by mid-June. Cleavage polyembryony was not observed. Embryos were mature by mid-August and most seed was shed in September and October.The potential seed set was only 16 seeds per cone and filled seed averaged only 2.6 per cone. Most potential seed was lost because of early ovule abortion from unknown causes, insect damage, or low temperatures at or shortly after pollination. Some potential seeds were lost because the ovules were not pollinated or the embryos aborted. These seeds were soft but nearly normal appearing and contained spongy female gametophyte tissue. Methods of maximizing seed production are suggested.

scholarly journals In situ X-ray scattering evaluation of heat-induced ultrastructural changes in dental tissues and synthetic hydroxyapatite

2014 ◽  
Vol 11 (95) ◽  
pp. 20130928 ◽  
Author(s):  
Tan Sui ◽  
Michael A. Sandholzer ◽  
Alexander J. G. Lunt ◽  
Nikolaos Baimpas ◽  
Andrew Smith ◽  
...  
Keyword(s):  
Heat Exposure ◽  
Organic Matrix ◽  
Material Design ◽  
Ultrastructural Changes ◽  
X Ray ◽  
Ultrastructural Alterations ◽  
Dental Tissues ◽  
X Ray Scattering ◽  
Ray Scattering

Human dental tissues consist of inorganic constituents (mainly crystallites of hydroxyapatite, HAp) and organic matrix. In addition, synthetic HAp powders are frequently used in medical and chemical applications. Insights into the ultrastructural alterations of skeletal hard tissues exposed to thermal treatment are crucial for the estimation of temperature of exposure in forensic and archaeological studies. However, at present, only limited data exist on the heat-induced structural alterations of human dental tissues. In this paper, advanced non-destructive small- and wide angle X-ray scattering (SAXS/WAXS) synchrotron techniques were used to investigate the in situ ultrastructural alterations in thermally treated human dental tissues and synthetic HAp powders. The crystallographic properties were probed by WAXS, whereas HAp grain size distribution changes were evaluated by SAXS. The results demonstrate the important role of the organic matrix that binds together the HAp crystallites in responding to heat exposure. This is highlighted by the difference in the thermal behaviour between human dental tissues and synthetic HAp powders. The X-ray analysis results are supported by thermogravimetric analysis. The results concerning the HAp crystalline architecture in natural and synthetic HAp powders provide a reliable basis for deducing the heating history for dental tissues in the forensic and archaeological context, and the foundation for further development and optimization of biomimetic material design.

scholarly journals Ultrastructural study of maturing pollen in Arabidopsis thaliana (L.) Heynh. (Brassicaceae)

2014 ◽  
Vol 66 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Krystyna Zając
Keyword(s):  
Arabidopsis Thaliana ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Spherical Shape ◽  
Ultrastructural Changes ◽  
Lipid Bodies ◽  
Cell Cytoplasm ◽  
Cell Form ◽  
Microspore Stage ◽  
Pollen Stage

Ultrastructural changes in <em>Arabidopsis thaliana</em> pollen, between late microspore stage and mature pollen stage were described. When the generative cell was peeled off from the intine, it was of spherical shape and had all usual organelles with the exception of plastids. The cytoplasm transformation of the vegetative cell included an increase in the number of mitochondria and changes in the accumulation of starch and lipid bodies. The starch plastids were observed at the bicellular and early tricellular pollen stages and next starch was utilized during the maturation procces. The lipid bodies of the vegetative cell form a very regular sheath around the generative cell and then, around the sperm cells. Before anthesis the lipid bodies were dispersed within the whole vegetative cell cytoplasm.

scholarly journals Correlated seed failure as an environmental veto to synchronize reproduction of masting plants

2017 ◽  
Author(s):  
Michał Bogdziewicz ◽  
Michael A. Steele ◽  
Shealyn Marino ◽  
Elizabeth E. Crone
Keyword(s):  
Seed Production ◽  
Large Scale ◽  
Pollen Limitation ◽  
Reproductive Failure ◽  
Pollination Success ◽  
Proximate Mechanisms ◽  
Weather Events ◽  
Resource Dynamics ◽  
Resource Budget Model ◽  
Necessary And Sufficient

Highly variable, synchronized seed production, called masting, is a widespread reproductive strategy in plants. Resource dynamics, pollination success, and, as described here, environmental veto, are possible proximate mechanisms of masting. We extended the resource budget model of masting with correlated and uncorrelated reproductive failure, and ran this model across its parameters space. Next, we parametrized the model based on a 16-year seed production data for red (Quercus rubra) and white (Q. alba) oaks. Simulations showed that resource dynamics and reproduction failure produce masting even in the absence of pollen coupling. In concordance, in both species, among-year variation in resource gain and correlated reproductive failure were necessary and sufficient to produce masting. Environmental variation is a form of reproduction failure caused by environmental veto that may drive large-scale synchronization without density-dependent pollen limitation. Reproductive-inhibiting weather events are prevalent in ecosystems, suggesting that these described mechanisms likely operate in many masting systems.

scholarly journals Change of physical and chemical properties clinoptilolite after mechanical activation

2015 ◽  
Vol 11 (2) ◽  
pp. 58-61
Author(s):  
Anastasiya G Bebiya ◽  
Pavel Y Gulyaev ◽  
Irina V Milyukova
Keyword(s):  
Mechanical Activation ◽  
Chemical Properties ◽  
Optimal Time ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sorption Ability ◽  
Maximum Sorption ◽  
Activation Times ◽  
Physical And Chemical ◽  
And Chemical Properties

Presents experimental data depending on the specific surface area and sorption properties of the clinoptilolite powder mechanical activation times. Carried out X-ray diffraction and spec-troscopic analysis of mechanically activated zeolite. Find the optimal time and mechanical activation modes which relate the maximum sorption ability.

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