Bud development in western hemlock. I. Annual growth cycle of vegetative buds

1973 ◽  
Vol 51 (11) ◽  
pp. 2223-2231 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Mitotic Activity ◽  
Shoot Elongation ◽  
Growth Cycle ◽  
Leaf Primordia ◽  
Annual Growth ◽  
Western Hemlock ◽  
Bud Burst ◽  
Bud Development ◽  
Vegetative Buds ◽  
Number Of Leaves

Vegetative apices of mature Tsnga heterophylla (Raf.) Sarg. were studied throughout the annual growth cycle. Apices become mitotically active during the last week of March. Leaf primordia elongate, causing the buds to swell, while the apex remains small and produces bud scales. Axillary buds are initiated about mid-April. Little shoot elongation occurs before vegetative buds burst in mid-May. After bud burst, rapid shoot elongation occurs for about 7 weeks, during which time the apex also elongates and the rest of the bud scales are initiated. There is a marked increase in mitotic activity in the apex during the transition from bud-scale initiation to leaf initiation, which occurs early in July when the grand phase of shoot elongation is complete. This is believed to be the time when vegetative apices undergo transition to become reproductive apices. Leaf primordia are initiated in rapid succession until mid-August, when two-thirds of the final number of leaves are initiated and the subtending shoot is fully elongated. From mid-August until mid-November, no shoot elongation occurs, leaf primordia are initiated more slowly, and mitotic activity in the apex gradually decreases. After all of the next season's leaves have been initiated, about mid-November, mitotic activity in the apex stops and the vegetative buds become dormant.

Bud development in Sitka spruce. I. Annual growth cycle of vegetative buds and shoots

1976 ◽  
Vol 54 (3-4) ◽  
pp. 313-325 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Early Period ◽  
Shoot Elongation ◽  
Growth Cycle ◽  
Picea Sitchensis ◽  
Leaf Primordia ◽  
Annual Growth ◽  
Bud Burst ◽  
Leaf Initiation ◽  
Number Of Leaves ◽  
Vegetative Bud

Vegetative apices of Picea sitchensis (Bong.) Carr. were studied throughout the annual growth cycle. Apices became mitotically active late in March and the shoot axis and leaf primordia elongated causing the bud to swell. New axillary apices were initiated in mid-April and the terminal apex and new axillary apices initiated bud scales until early in July. Vegetative bud burst occurred early in June and shoot elongation was completed by mid-July. The end of shoot elongation coincided with the onset of leaf initiation. The change from bud-scale to leaf initiation was characterized by a period of increased mitotic activity and rapid apical growth. About half of the final number of leaves were initiated during the early period of rapid leaf initiation. The remaining leaf primordia were initiated more slowly over the next 3 months. Buds became dormant by mid-November.

Bud development in Picea engelmannii. I. Vegetative bud development, differentiation, and early development of reproductive buds

1983 ◽  
Vol 61 (9) ◽  
pp. 2291-2301 ◽  
Author(s):  
Derek L. S. Harrison ◽  
John N. Owens
Keyword(s):  
Shoot Elongation ◽  
Longitudinal Axis ◽  
Leaf Primordia ◽  
Axillary Buds ◽  
Picea Engelmannii ◽  
Bud Burst ◽  
Bud Development ◽  
Vegetative Buds ◽  
Terminal Buds ◽  
Mother Cells

Vegetative buds of Engelmann spruce (Picea engelmannii Parry) from the Prince George Forest District (British Columbia) were collected and studied. In mid-April, dormancy ended as determined from mitotic divisions within the leaf primordia; 2 weeks later mitotic activity occurred in the bud apices. Bud-scale initiation began in terminal buds by late May followed by that in axillary buds 2 weeks later. Shoot elongation began in late May, bud burst occurred in late June, and both shoot elongation and bud-scale initiation were complete by late July. Terminal buds began to differentiate by the initiation of leaf primordia, into vegetative buds early in August whereas axillary buds began to differentiate 1 week later. Leaf initiation was completed in all vegetative buds by late September and buds were dormant by mid-October. Pollen cones initiated microsporophylls after bud-scale initiation. Microsporangial initiation began in late August. Microsporangial enlargement began in mid-September and continued until dormancy when pollen mother cells were observed in a premeiotic stage. Seed cones initiated bracts directly after bud-scale initiation. In mid-August, ovuliferous scales began to be initiated. Two ovule primordia formed adaxially, one on each side of the median longitudinal axis of each ovuliferous scale. Each ovule formed one large central megaspore mother cell which overwintered in a premeiotic stage.

Bud development in Picea glauca. I. Annual growth cycle of vegetative buds and shoot elongation as they relate to date and temperature sums

1977 ◽  
Vol 55 (21) ◽  
pp. 2728-2745 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder ◽  
Hilary Langer
Keyword(s):  
Picea Glauca ◽  
Shoot Growth ◽  
Shoot Elongation ◽  
Growth Cycle ◽  
Bud Dormancy ◽  
Annual Growth ◽  
Bud Development ◽  
Leaf Initiation ◽  
Vegetative Buds ◽  
Vegetative Bud

Vegetative buds of Picea glauca (Moench) Voss were studied throughout the annual growth cycle in several trees in 1975 and 1976 and bud development was related to lateral vegetative shoot growth, date, and temperature sums.Vegetative buds became mitotically active in mid-April at lower elevations and about 6 weeks later at higher elevations. Shoot elongation was characterized by similar smooth sigmoid curves in both years. Shoot growth was slow for the 1st month, rapid during the 2nd month, and slow again for the 3rd month and ended by early August. Temperature sums related best to percentage of shoot elongation if the end of vegetative bud dormancy was used as the starting date and 5 °C was used as the threshold temperature. Arbitrarily chosen starting dates and threshold temperatures gave temperature sums which were related to shoot elongation only when shoot elongation was nearly completed. Generally, if the end of vegetative bud dormancy is known, the number of days from that time is nearly as accurate as the more complex use of temperature sums in predicting the percentage of shoot elongation or the stage of vegetative bud development.Bud-scale initiation occurred during shoot elongation. Axillary buds were initiated in mid-May and flushing occurred when shoots had elongated to about 30% of their final length in late May or early June. The end of shoot elongation coincided with the onset of leaf initiation on all trees in both years. The change from bud-scale initiation to leaf initiation was preceded by a marked increase in apical width and a slight increase in apical height and mitotic frequency. Leaf initiation was rapid for 6 weeks then slower for the last 4 weeks. Vegetative buds became dormant in mid-October.Vegetative bud development is closely related to shoot elongation. Breaking of vegetative bud dormancy was not affected by temperature but shoot elongation and flushing were affected by temperatures which occurred after dormancy was broken.

Bud development in grand fir (Abiesgrandis)

1984 ◽  
Vol 14 (4) ◽  
pp. 575-588 ◽  
Author(s):  
John N. Owens
Keyword(s):  
Shoot Elongation ◽  
Lower Surface ◽  
Growth Cycle ◽  
Axillary Buds ◽  
Bud Burst ◽  
Leaf Initiation ◽  
Cone Production ◽  
Vegetative Buds ◽  
Seed Cone ◽  
Terminal Buds

Vegetative buds of mature Abiesgrandis (Dougl.) Lindl. (grand fir) were studied throughout the annual growth cycle. Vegetative buds became mitotically active in mid-March, bud burst occurred in mid-May, and shoot elongation continued until the end of June. Bud scales were initiated during shoot elongation. In mid-April axillary buds were initiated on elongating shoots. They were initiated subterminally in the axils of the first-formed bud scales and laterally in the axils of leaf primordia. Axillary buds followed the same developmental sequence as terminal buds. The end of bud-scale initiation was preceded by rapid apical enlargement and followed by a period of rapid leaf initiation. The rate of leaf initiation slowed in mid-August but continued until vegetative buds became dormant in mid-November. Seed cones are axillary on the upper surface of vigorous shoots in the upper region of the crown. Pollen cones are axillary on the lower surface of shoots below the seed cone bearing region of the crown. Bract and microsporophyll initiation began in early to mid-July, was rapid at first, until about two-thirds of the primordia were initiated, then slower until all primordia were initiated. All bracts and ovuliferous scales were initiated and seed-cone buds became dormant in early November. All microsporophylls were initiated by early September, microsporangial development began in mid-August, and pollen-cone buds became dormant in early November. The cyclic nature of cone production in Abies is discussed in relation to cone-bud initiation, cone maturation, and photosynthate utilization in developing shoots.

Vegetative bud development and the time and method of cone initiation in subalpine fir (Abies lasiocarpa)

1982 ◽  
Vol 60 (11) ◽  
pp. 2249-2262 ◽  
Author(s):  
John N. Owens ◽  
Hardev Singh
Keyword(s):  
Shoot Elongation ◽  
Axillary Bud ◽  
Abies Lasiocarpa ◽  
Bud Burst ◽  
Rapid Phase ◽  
Bud Development ◽  
Vegetative Buds ◽  
Seed Cone ◽  
Pollen Cone ◽  
Vegetative Bud

Vegetative terminal and axillary bud development and the time and method of cone initiation and cone bud development are described for Abies lasiocarpa (Hook.) Nutt.Cell divisions began in vegetative buds early in April. A brief period of apical enlargement was followed by bud-scale initiation for 10 weeks. Buds were initiated in the axils of some leaf primordia about the time of vegetative bud burst, 1 month after vegetative bud dormancy ended. All buds completed bud-scale initiation by the end of June, which coincided with the end of the rapid phase of lateral shoot elongation. This was followed by a 2-week period of bud differentiation, during which time few primordia were initiated, apical size increased, and apical shape and zonation changed more in reproductive than in vegetative apices. Leaf and bract initiation began by mid-July and continued until mid-October, when vegetative and seed-cone buds became dormant. Microsporophyll initiation began earlier and was nearly completed by the end of July; pollen-cone buds became dormant in mid-September.The number of cone buds is determined by the proportion of axillary bud primordia that fully developed and the pathway along which they developed. Potential seed-cone buds may become latent but more commonly differentiate into vegetative buds of low vigor. Potential pollen-cone buds frequently become latent but have not been observed to differentiate into vegetative buds. The position of the axillary bud on the shoot and of the shoot in the tree strongly influences axillary bud development in Abies.

Vegetative bud development and cone differentiation in Abies amabilis

1977 ◽  
Vol 55 (8) ◽  
pp. 992-1008 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Shoot Elongation ◽  
Leaf Primordia ◽  
Bud Burst ◽  
Lateral Shoot ◽  
Vegetative Buds ◽  
Seed Cone ◽  
Mitotic Frequency ◽  
Mother Cells ◽  
Pollen Cone ◽  
Vegetative Bud

In the trees studied, vegetative buds began development in early April, bud burst occurred in early June and shoot elongation was completed by late July. Vegetative buds initiated bud scales from mid-April until mid-July and then initiated leaf primordia until the vegetative buds became dormant in November. All axillary buds were initiated in mid-May and their bud scales were initiated until early July. During bud-scale initiation, distal vegetative lateral apices were more conical but had a mitotic frequency similar to other lateral apices. Near the end of bud-scale initiation, vegetative apices accumulated more phenolic and ergastic compounds in future pith cells than did potential seed-cone or pollen-cone apices. Bud differentiation occurred in mid-July at the end of lateral shoot elongation. During bud differentiation the mitotic frequency of pollen-cone and seed-cone apices increased much more than that of distal vegetative apices. This resulted in a marked increase in apical size and a change in apical shape and zonation that made reproductive apices easily distinguishable from vegetative apices. Bracts began to be initiated in mid-July, and ovuliferous scales, in mid-August. Both continued to be initiated until seed-cone buds became dormant in November. A single megaspore mother cell formed in each ovule before dormancy. Microsporophylls were initiated from mid-July until early September. Microsporangia began to differentiate in September and contained microspore mother cells when pollen cones became dormant in mid-October. Meiosis did not begin before dormancy. A few potential vegetative and many potential seed-cone and potential pollen-cone apices became latent during bud-scale initiation. Some potential seed-cone apices became vegetative buds. Consequently, the number of cone buds formed was determined primarily by the proportion of apices that developed fully and the pathway along which they developed.

Bud development in Larix occidentalis. I. Growth and development of vegetative long shoot and vegetative short shoot buds

1979 ◽  
Vol 57 (7) ◽  
pp. 687-700 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Growth And Development ◽  
Shoot Elongation ◽  
Growth Cycle ◽  
Leaf Primordia ◽  
Axillary Buds ◽  
Larix Occidentalis ◽  
Short Shoot ◽  
Bud Development ◽  
Shoot Buds ◽  
Vegetative Bud

Vegetative terminal long shoot buds (TLSB) and short shoot buds (SSB) were studied throughout the annual growth cycle in several trees over several years. TLSB were not totally preformed. The dormant TLSB consisted of bud scales enclosing some basal leaves and both were borne on a broad receptacle. Centripetal to the basal leaves, a series of axial leaf primordia was borne on the flanks of the apex. After dormancy a second series of axial leaves was initiated above those initiated before dormancy. Basal and both series of axial leaves elongated during shoot elongation as the terminal apex again initiated axial leaves, bud scales, and then basal leaves. After shoot elongation the first series of axial leaves was initiated before the TLSB became dormant in October. No dimorphism occurred between predormancy and postdormancy axial leaves or axial and basal leaves. Axilliary buds were initiated in the TLSB about the time of flushing. All leaves did not bear axillary buds. All axillary buds rapidly initiated a series of bud scales and then entered a slower phase of bud-scale initiation and rapid apical enlargement. Leaf primordia then were initiated at the base of the apex and borne on the broad receptacle. Apices then differentiated into axillary long shoot buds (ALSB) or SSB. ALSB developed similarly to TLSB, whereas axillary SSB initiated leaf primordia at the base of the apex and all but the last primordia to be initiated were borne on the broad receptacle. Axillary SSB were preformed but ALSB were not completely preformed and both became dormant in mid-October. The apex of a short shoot lived for up to 8 to 10 years. In each successive year it passed through phases of bud-scale initiation and leaf initiation to form a dormant preformed SSB which flushed after overwintering. Annual short shoot elongation was about 1 mm. The LSB and SSB apices varied in shape and size during the year but apical zonation was similar in all apices. Larix vegetative bud development is compared with that found in other gymnosperms.

Bud development in mountain hemlock (Tsuga mertensiana). I. Vegetative bud and shoot development

1984 ◽  
Vol 62 (3) ◽  
pp. 475-483 ◽  
Author(s):  
John N. Owens
Keyword(s):  
Growth Cycle ◽  
Shoot Development ◽  
Bud Development ◽  
Vegetative Buds ◽  
Lateral Shoots ◽  
Tsuga Mertensiana ◽  
Terminal Buds ◽  
Lateral Branches ◽  
Relationship Of ◽  
Vegetative Bud

Vegetative buds of mature Tsuga mertensiana (Bong) Carr. (mountain hemlock) were studied throughout the annual growth cycle. Cell divisions began in vegetative buds in mid-April and shoots and leaves elongated within the bud scales causing the buds to burst in late June. Lateral shoots completed elongation by the end of July. Vegetative terminal apices from lateral branches began bud-scale initiation when bud dormancy ended. All bud scales were initiated by the end of July. Leaf primordial initiation occurred from that time until mid-October when vegetative buds again became dormant. Axillary buds were initiated on the elongating shoots in early June then followed the same phenology as vegetative terminal buds. Vegetative bud and shoot development are compared with that of western hemlock and certain other members of the Pinaceae. The relationship of bud development to shoot development is discussed for mountain hemlock and other conifers having a similar pattern of vegetative bud development.

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

1989 ◽  
Vol 19 (8) ◽  
pp. 1051-1058 ◽  
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.

A study of DNA and mitotic activity in the vegetative apex of Douglas fir during the annual growth cycle

1973 ◽  
Vol 51 (7) ◽  
pp. 1395-1409 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Mitotic Activity ◽  
Dna Content ◽  
Peripheral Zone ◽  
Growth Cycle ◽  
Nuclear Volume ◽  
Annual Growth ◽  
Axillary Shoots ◽  
Volume Percentage ◽  
Leaf Initiation ◽  
Mother Cells

Vegetative apices of Pseudotsuga menziesii (Mirb.) Franco were studied throughout the annual growth cycle. When observations based on anatomy, histochemistry, and external morphology are combined, the growth cycle of the vegetative apex should be subdivided into five stages: (1) dormancy, (2) early bud-scale initiation, (3) late bud-scale initiation and rapid apical enlargement, (4) early, rapid leaf initiation, and (5) late, slow leaf initiation. The same cytohistological zonation pattern is present in vegetative apices throughout the growth cycle and usually consists of apical, peripheral, and rib meristem zones. During dormancy, early bud-scale initiation, and early leaf initiation, the apical zone is separated into apical initials and central mother cells based on nuclear characteristics and mitotic activity. Cytohistological zonation is supported by constant differences in nuclear volume, mitotic activity, and DNA content between zones. The peripheral zone is mitotically more active than the apical zone; however, the apical zone is not quiescent. Zones vary in size, prominence, and mitotic activity, which often relates to a particular developmental stage of the apex. The dormant apex has no mitotic activity, and cytohistological zonation is present but not distinct. Zonation increases throughout the first half of the growing season, reaches a maximum during late bud-scale and early leaf initiation, and decreases as dormancy approaches. In general, increases in nuclear volume, percentage of nuclei at 4C, and average DNA content per nucleus correlate with increases in the prominence of zonation. Zonation did not result from different zones being "held" at certain C levels of DNA. Although nuclear volume was used in calculating the DNA content, the DNA level often varied independently of volume. Mitotic activity and dormancy appear to be related to carbohydrate levels within the bud and subtending shoot. The period of most prominent zonation is also the period of most active primordial initiation, largest apical size, and the time when new axillary shoots become determined in their pathway of development.

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