THE INITIATION AND EARLY DEVELOPMENT OF THE SEED CONE OF DOUGLAS FIR

1964 ◽  
Vol 42 (8) ◽  
pp. 1031-1047 ◽  
Author(s):  
John N. Owens ◽  
Frank H. Smith
Keyword(s):  
Early Development ◽  
Subsequent Development ◽  
Peripheral Zone ◽  
Leaf Axil ◽  
Cortical Cells ◽  
Lateral Buds ◽  
Seed Cone ◽  
Lateral Shoots ◽  
Similar Growth ◽  
Growth Periodicity

The initiation and early development of lateral vegetative, megasporangiate, and microsporangiate buds is described. The subsequent development of the megasporangiate cone prior to dormancy is described in detail. Initiation of lateral buds from cortical cells above the leaf axil occurs early in April and is similar in the three bud types. Apical zonation becomes apparent by mid-May but is less distinct in the microsporangiate primordium because of its smaller size. The microsporangiate bud remains distinctly smaller until microsporophyll initiation. Apical enlargement occurs in mid-July, at the end of the period of cataphyll initiation, and marks the onset of subsequent foliar initiation (leaves, bracts, and microsporophylls). Like the cataphylls, these foliar organs are presaged by procambial differentiation from the peripheral zone outward to the base of the presumptive primordium. No distinct apical initials appear in any of the foliar organs. A group of subapical initials is active during early development but they soon differentiate and further elongation occurs by intercalary growth. Bract initiation ends early in October. The apices of the three bud types show a similar growth periodicity and become greatly reduced in size and distinctness of zonation during foliar initiation. Scale initiation in the megasporangiate bud begins early in September and continues until the cones become dormant early in November. Scales are initiated from axillary cells at the base of the bracts. Apical zonation similar to other lateral shoots is present during early development but the organization changes to a type of submarginal growth.

DEVELOPMENT OF THE SEED CONE OF DOUGLAS-FIR FOLLOWING DORMANCY

1965 ◽  
Vol 43 (2) ◽  
pp. 317-332 ◽  
Author(s):  
John N. Owens ◽  
Frank H. Smith
Keyword(s):  
Early Development ◽  
Maximum Size ◽  
Developmental Cycle ◽  
Surface Layers ◽  
Adaxial Surface ◽  
Single Leaf ◽  
Separate Branch ◽  
Cycle Growth ◽  
Seed Cone ◽  
Lateral Shoots

Development of the megasporangiate cone during the period of enlargement and maturation following dormancy is described in detail. This work, in conjunction with the early development previously described, provides a complete description of the 17 month developmental cycle. Growth of the megasporangiate cone is resumed in early March near Corvallis, Oregon, and the cone buds burst about 1 month later. The cone elongates rapidly by intercalary growth. Bracts enlarge but the shape of the bract established prior to dormancy is essentially maintained. The scale assumes a spoon-shaped appearance as a result of a form of marginal growth. Vascularization, and development of other tissues within the bract and scale, indicates that bracts are homologous to leaves and basically similar in structure, but scales are highly modified fertile lateral shoots. Each bract is supplied by a single leaf trace and each scale by two separate branch traces. The seed wings differentiate from adaxial surface layers of each scale. A large zone of macrosclereids differentiates in the basal abaxial portion of the scale. The cone reaches its maximum size early in July and maturation of tissues occurs in July and August, and is generally complete early in September. Cone opening results from drying and shrinkage of the macrosclereids at the base of the scale.

Changes in the rate of cell divisions in the course of early development of diploid and haploid loach embryos

Development ◽  
1968 ◽  
Vol 20 (2) ◽  
pp. 141-150
Author(s):  
N. N. Rott ◽  
G. A. Sheveleva
Keyword(s):  
Cell Division ◽  
Early Development ◽  
Subsequent Development ◽  
Nuclear Function ◽  
Second Stage ◽  
Cell Divisions ◽  
Genetic Activity ◽  
Synchronous Cell ◽  
Nuclear Synthesis ◽  
Two Stages

The period of development preceding gastrulation can be divided into two stages. The first is characterized by rapid synchronous cell division. True interphase, which is characterized by the fusion of karyomers and the occurrence of a nucleolus, is absent at this stage. During the second stage the rate of cell division decreases and divisions are asynchronous. The process of cell division is antagonistic to genetic activity of nuclei, as nuclear synthesis of m-RNA appears to cease during mitosis. Consequently, one can suggest that the increase of the length of interphase is necessary for the onset of morphogenetic nuclear function, which ensures gastrulation and subsequent development (Neyfakh, 1959). The present investigation was designed first to determine exactly the time of the appearance of the changes in the rate of cell division and to compare it with the time of onset of morphogenetic nuclear function.

scholarly journals A POSSIBLE MECHANISM FOR THE MORPHOGENESIS OF LAMELLAR SYSTEMS IN PLANT CELLS

1956 ◽  
Vol 2 (5) ◽  
pp. 597-608 ◽  
Author(s):  
A. J. Hodge ◽  
J. D. McLean ◽  
F. V. Mercer
Keyword(s):  
Normal Development ◽  
Layer Structure ◽  
Subsequent Development ◽  
Peripheral Zone ◽  
Compound Layer ◽  
Prolamellar Body ◽  
Membrane Structures ◽  
Prolamellar Bodies ◽  
Precursor Material ◽  
The Individual

A mechanism for the formation of lamellar systems in the plant cell has been proposed as a result of electron microscope observations of young and mature cells of Nitella cristata and the plastids of Zea mays in normal plants, developing plants, and certain mutant types. The results are compatible with the concept that lamellar structures arise by the fusion or coalescence of small vesicular elements, giving rise initially to closed double membrane Structures (cisternae). In the chloroplasts of Zea, the cisternae subsequently undergo structural transformations to give rise to a compound layer structure already described for the individual chloroplast lamellae. During normal development, the minute vesicles in the young chloroplast are aggregated into one or more dense granular bodies (prolamellar bodies) which often appear crystalline. Lamellae grow out from these bodies. In fully etiolated leaves lamellae are absent and the prolamellar bodies become quite large, presumably because of inhibition of the fusion step which appears to require chlorophyll. Lamellae develop rapidly on exposure of the plant to light, and subsequent development closely parallels that seen under normal conditions. The plastids of white and very pale green mutants of Zea similarly lack lamellae and contain only vesicular elements. A specialized peripheral zone immediately below the double limiting membrane in Zea chloroplasts appears to be responsible for the production of vesicles. These may be immediately converted to lamellae under normal conditions, but accumulate to form a prolamellar body if lamellar formation is prevented, as in the case of etiolation and chlorophyll-deficient mutation, or when the rate of lamellar formation is slower than that of the production of precursor material (as appears to be the case in the early stages of normal development).

scholarly journals The Nature of Shoot Dominance in White Yam Tubers (Dioscorea rotundata Poir)

1969 ◽  
Vol 68 (4) ◽  
pp. 335-340
Author(s):  
Osi Mozie
Keyword(s):  
Apical Dominance ◽  
Distal Region ◽  
Proximal Region ◽  
Basal Region ◽  
Middle Region ◽  
Ambient Conditions ◽  
Dioscorea Rotundata ◽  
Lateral Buds ◽  
Lateral Shoots ◽  
White Yam

The nature of shoot dominance in white yam tubers (Dioscorea rotundata Poir) was studied under ambient conditions in the conventional yam storage barn. Whole tubers sprouted only at the proximal ends (i.e. the morphological bases). The single basal shoot formed per sprouting whole tuber inhibited the formation of lateral shoots along the tuber axis. Separating the basal end by sectioning the tuber into three regions namely "head" (i.e. basal or proximal region), middle region and "tail" (i.e. apical or distal region), appeared to stimulate the formation of lateral shoots on the surfaces of the tuber pieces below the basal region. Separating the basal region from the entire tuber by sectioning appeared to remove the stress under which the lateral buds had existed in the intact tuber. This response indicated a strong "basal dominance" of basal shoots in sprouting intact or whole yam tubers. The physiology of shoot dominance in whole yam tubers could be described as "basal dominance" rather than "apical dominance", since in sprouting intact or whole tuber it is the basal shoot (i.e. shoot of the morphological base or proximal end) that inhibits the development of lateral shoots along the tuber axis.

Bud development in Sitka spruce. II. Cone differentiation and early development

1976 ◽  
Vol 54 (8) ◽  
pp. 766-779 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Phenolic Compounds ◽  
Early Development ◽  
Shoot Elongation ◽  
Picea Sitchensis ◽  
Lateral Shoot ◽  
Bud Development ◽  
Seed Cone ◽  
Mitotic Frequency ◽  
Mother Cells ◽  
Pollen Cone

Pollen-cone and seed-cone buds of Picea sitchensis (Bong.) Carr. are found as either terminal or axillary buds. Pollen cones are most likely to develop from small axillary apices on vigorous distal shoots or small terminal apices on less vigorous, proximal shoots. Seed cones are most likely to develop from large, distal axillary apices on vigorous shoots or smaller terminal apices on less vigorous shoots. All apices became mitotically active late in March, passed through a 3.5-month period of bud-scale initiation, and in mid-July became differentiated as vegetative, pollen-cone, or seed-cone apices. Potentially pollen-cone apices were smaller, had a lower mitotic frequency during bud-scale initiation, and produced fewer bud scales than apices which developed into seed-cone or vegetative buds. During bud-scale initiation all apices had a few strands of cells containing phenolic compounds in the developing pith. At the time of bud differentiation, the pith of vegetative apices accumulated more phenolic compounds and non-phenolic ergastic materials, whereas the pith of reproductive apices did not. This was followed by a marked increase in mitotic frequency in reproductive apices, resulting in changes in apical size and shape. Leaf, bract, and microsporophyll initiation began about the end of July. All microsporophylls were initiated by the end of August. Sporogenous cells developed, but meiosis did not occur before the pollen cones became dormant at the end of October. Two-thirds of the bracts were initiated by the end of August. The remaining bracts were initiated more slowly until dormancy. Ovuliferous scales were initiated for 3 months beginning in September, and megaspore mother cells appeared but did not undergo meiosis before seed cones became dormant at the end of November. There was no difference in the time of vegetative, pollen-cone, and seed-cone bud differentiation, which occurred at the end of lateral shoot elongation.

Shoot ontogeny in Arctostaphylos uva-ursi (bearberry): the annual cycle of apical activity

1984 ◽  
Vol 62 (9) ◽  
pp. 1925-1932 ◽  
Author(s):  
W. R. Remphrey ◽  
T. A. Steeves
Keyword(s):  
Leaf Primordia ◽  
Growth Strategy ◽  
Bud Burst ◽  
Foliage Leaf ◽  
Lateral Buds ◽  
Previous Season ◽  
Lateral Shoots ◽  
Terminal Buds ◽  
Floral Bracts ◽  
Vegetative Bud

Phenological investigation of shoot ontogeny in the prostrate shrub Arctostaphylos uva-ursi (L.) Spreng. (bearberry) at two sites in Saskatchewan, Canada, revealed that most growth occurred from May to July. Vegetative bud swell and leaf primordium initiation began around the 1st of May. Following bud burst in late May, elongation of most shoots continued for 3 to 5 weeks. Most bearberry shoots were not completely preformed; that is, several neoformed foliage leaves were initiated during current-year shoot extension in addition to the leaves that had been preformed during the previous season and had overwintered in the bud. In many shoots, a terminal inflorescence was initiated in the latter part of May of the year prior to anthesis. During conversion to the flowering state, the terminal apex initiated seven to nine floral bracts, each subtending a bud. In vegetative terminal shoots, bud-scale initiation also began in mid-May to late May and new terminal buds were first evident in early to mid-June. Following the initiation of bud scales and transitional leaves, the production of preformed foliage-leaf primordia continued until about August 1. Protruding lateral buds were evident histologically in the axils of preformed leaves during the initial stages of bud swell. On long, dominant shoots numerous neoformed leaves were initiated and shoot extension was often prolonged well into August. Second-flush terminal and lateral shoots, which resulted from the expansion of neoformed leaves and internodes, were also observed. The occurrence of neoformed growth in a large proportion of shoots suggests an exploitive, opportunistic growth strategy in this species.

Timing of insecticidal sprays to control the wheat-bulb fly, Leptohylemyia coarctata (Fall.)

1969 ◽  
Vol 58 (4) ◽  
pp. 793-801 ◽  
Author(s):  
D. C. Griffiths ◽  
G. C. Scott
Keyword(s):  
Field Trial ◽  
Large Field ◽  
Leaf Stage ◽  
Stage Of Development ◽  
Lateral Buds ◽  
Sowing Dates ◽  
Lateral Shoots ◽  
Fly Larvae ◽  
Main Growth ◽  
Shoot Meristems

The timing of sprays in relation to the stage of development of wheat plants and larvae of the wheat-bulb fly, Leptohylemyia coarctata (Pall.), was studied in the laboratory and field. The main growth of young wheat plants was of the centre shoot and such plants died when the centre shoot meristems were destroyed. Older plants survived by growth of lateral shoots. Sprays of dimethoate, trichloronate and thionazin applied before the larvae had emerged did not kill many larvae in the soil, and only insecticide that entered the plants was effective. Severely attacked two-leaf plants yielded little, whether sprayed or not, whereas three-leaf plants sprayed in early March gave a worth-while increase in yield: older plants had enough shoots to give moderate yields even when not sprayed.In a large field trial, plants from two sowing dates, 22nd October and 1st November, were both at the late two-leaf stage of growth in late February. Wheat-bulb fly larvae had entered nearly all the shoots but plants from both sowings had buds or small lateral growths hidden beneath the outer leaves. The yields of October-sown plots sprayed on 22nd February, 2nd March, 9th March or 16th March were 28·2, 28·8, 25·5 and 23·2 cwt. grain per acre, respectively, (yield of unsprayed plots = 18.9 cwt./acre) and of November-sown plots were 31·0, 27·5, 17·9 and 14·9 cwt. per acre, respectively, (yield of unsprayed plots = 116 cwt. per acre). Sprays had most effect when applied soon after larvae had entered the plants. Spraying severely-attacked late two-leaf to three-leaf plants gave the greatest benefits because these plants recovered by growth of lateral buds or small lateral shoots.

scholarly journals TREE TRAINING PROCEDURES FOR HIGH-DENSITY SWEET CHERRY PRODUCTION ON VIGOROUS ROOTSTOCKS

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1122d-1122 ◽  
Author(s):  
Stephen M. Southwick ◽  
James T. Yeager
Keyword(s):  
Shoot Formation ◽  
Training Methods ◽  
Lateral Shoot ◽  
High Productivity ◽  
Lateral Buds ◽  
Lateral Shoots ◽  
Sweet Cherries ◽  
Dormant Season ◽  
Spur Formation ◽  
Slow Growing

Sweet cherries produce vigorous upright growth from Apr.-Sept. and are slow to bear in California. Our tree training objectives include earlier bearing, easier harvesting, high productivity of good quality fruit. `Bing' cherry on mazzard and mahaleb rootstock were planted in 7 blocks and trained 6 ways. One group was headed 12-18 inches above the bud union and 4 branches were retained at the 1st dormant pruning. Lateral buds were treated with promalin at bud-break to induce lateral shoot formation. Trees were spring-summer pruned to reduce terminal growth. At the second dormant pruning, strong shoots were removed and lateral shoots were treated with promalin to induce spur formation. Trees were treated likewise through the 3rd dormant season and produced a fair crop in the 4th season. Central leader trees were created by tying/weighting limbs, dormant and summer pruning, and retaining less vigorous limbs as well as utilizing promalin. Slow growing trees tended to bear fruit more rapidly. Both training methods yielded fruit in the 4th season while traditional pruning procedures produced few fruit. Data and procedures will be presented to document these practices.

scholarly journals Early Development of Powdery Mildew on Cucumber Leaves Acclimatized to Illumination with Different Red-to-far-red Ratios

HortScience ◽  
2016 ◽  
Vol 51 (5) ◽  
pp. 530-536 ◽  
Author(s):  
Kaori Itagaki ◽  
Toshio Shibuya ◽  
Motoaki Tojo ◽  
Ryosuke Endo ◽  
Yoshiaki Kitaya
Keyword(s):  
Powdery Mildew ◽  
Early Development ◽  
Near Infrared ◽  
Light Emitting Diode ◽  
Subsequent Development ◽  
Conidial Germination ◽  
Limiting Factors ◽  
Powdery Mildew Fungus ◽  
Light Emitting ◽  
Conidial Development

The development of powdery mildew fungus (Podosphaera xanthii) is suppressed on cucumber (Cucumis sativus L.) seedlings acclimatized to higher red-to-far-red ratio (R:FR) than natural R:FR (≈1.2), but its early development and any limiting factors are still unclear. The present study evaluated conidial germination, initial invasion, and subsequent development of P. xanthii on cucumber seedlings raised under light-emitting diode (LED) lights with R:FRs of 1.2, 5.0, or 10. There were no differences in conidial germination or initial invasion between the treatments, so there was no effect of acclimatization to R:FR on either. But, the development of hyphae, hyphal cells, and haustoria after inoculation were suppressed on seedlings acclimatized to higher R:FR. Because differences occurred only after the initial invasion, nonstructural properties of the host leaves may have affected conidial development. Higher R:FR also suppressed conidial development under natural light filtered through a photo-selective film, which absorbs near-infrared (NIR)-light. However, this effect was reduced when the plants were moved to natural R:FR after inoculation, possibly because of reacclimatization of the seedlings.

Growth response of young balsam fir fertilized with nitrogen, phosphorus, potassium, and lime

1977 ◽  
Vol 7 (3) ◽  
pp. 441-446 ◽  
Author(s):  
V. R. Timmer ◽  
E. L. Stone ◽  
D. G. Embree
Keyword(s):  
Growth Responses ◽  
Short Term ◽  
N Application ◽  
Christmas Trees ◽  
Lateral Buds ◽  
Lateral Shoots ◽  
Main Effect ◽  
Four Levels ◽  
Terminal Buds ◽  
Nitrogen Phosphorus

Growth responses of a young, naturally regenerated Abiesbalsamea stand managed for Christmas trees in Nova Scotia were measured over the 2 years after application of dolomitic limestone and factorial combinations of four levels of N, two levels of P, and two levels of K. In the first season, nitrogen-treated trees were darker green and had heavier terminal buds. Other significant responses owing to nitrogen were greater numbers of apical and lateral buds in the second season and greater length of leaders, lateral shoots, and needles in both seasons. The only significant main effect of P was on bud development. Neither K nor lime had any significant influence, and no significant interactions among any nutrients were detected. Growth responses did not differ significantly among three rates of N application over the 2-year period indicating.that for short-term cultural purposes the higher rates are inefficient on this site.

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