Development Time of ‘Cara Mia’ Rose Shoots as Influenced by Pruning Position and Parent Shoot Diameter1
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Abstract:
Abstract Shoots of ‘Cara Mia’ rose ( Rosa hybrida L.) arising from buds higher on the parent shoot become salable more quickly than those arising from lower buds. Those developing above the 10th or below the 6th true leaf are shorter, of smaller diameter and weigh less. Shoot development is also strongly influenced by shoot diameter at the point of origin. Larger parent shoots give rise to shoots that become salable more quickly, are longer, weigh more, and are larger in diameter than those from smaller parent shoots. Buds from larger-diameter shoots are of larger diameter and have more leaf primordia than those from smaller-diameter shoots, but the diameter of their apical dome is not greater.Keywords:
Primordium
Pruning
Lateral shoot
Apical dominance
A mature, quiescent, primary axillary bud on the main axis of a flowering Nicotiana tabacum cv. Wisconsin 38 plant, when released from apical dominance and before forming its terminal flower, produced a number of nodes which was dependent upon its position on the main axis. Each bud produced about one more node than the next bud above it. The total number of nodes produced by an axillary bud was about 6 to 8 greater than the number of nodes present above this bud on the main axis. At anthesis of the terminal flower on the main axis, mature, quiescent, primary axillary buds had initiated 7 to 9 leaf primordia while secondary axillary buds, sometimes present in addition to the primary ones, had initiated 4 to 5 leaf primordia. When permitted to grow out independently, primary and secondary axillary buds located at the same node on the main axis produced the same number of nodes before forming their terminal flowers. In contrast, immature primary axillary buds which had produced only 5 leaf primordia and which were released from apical dominance prior to the formation of flowers on the main axis produced only as many nodes as would be produced above them on the main axis by the terminal meristem, i.e., “extra” nodes were not produced. Therefore, it is the physiological status of the plant and not the number of nodes on the bud at the time of release from apical dominance that influenced the node‐counting process of a bud. When two axillary buds were permitted to develop on the same main axis, each produced the same number of nodes as single axillary buds developing at these nodes. Thus, the counting process in an axillary bud of tobacco is independent of other buds. Axillary buds on main axes of plants that had been placed horizontally produced the same number of nodes as identically‐positioned axillary buds on vertical plants, indicating that gravity does not play a major role in the counting, by an axillary bud, of the nodes on the main axis.
Primordium
Apical dominance
Bud
Lateral shoot
Main stem
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Primordium
Apical dominance
Bud
Lateral shoot
Main stem
Anthesis
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The influence of temperature on the timing of budbreak in woody perennials is well known, but its effect on subsequent shoot growth and architecture has received little attention because it is understood that growth is determined by current temperature. Seasonal shoot development of grapevines (Vitis vinifera) was evaluated following differences in temperature near budbreak while minimizing the effects of other microclimatic variables. Dormant buds and emerging shoots of field-grown grapevines were heated above or cooled below the temperature of ambient buds from before budbreak until individual flowers were visible on inflorescences, at which stage the shoots had four to eight unfolded leaves. Multiple treatments were imposed randomly on individual plants and replicated across plants. Shoot growth and development were monitored during two growing seasons. Higher bud temperatures advanced the date of budbreak and accelerated shoot growth and leaf area development. Differences were due to higher rates of shoot elongation, leaf appearance, leaf-area expansion and axillary-bud outgrowth. Although shoots arising from heated buds grew most vigorously, apical dominance in these shoots was reduced, as their axillary buds broke earlier and gave rise to more vigorous lateral shoots. In contrast, axillary-bud outgrowth was minimal on the slow-growing shoots emerging from buds cooled below ambient. Variation in shoot development persisted or increased during the growing season, well after temperature treatments were terminated and despite an imposed soil water deficit. The data indicate that bud-level differences in budbreak temperature may lead to marked differences in shoot growth, shoot architecture and leaf-area development that are maintained or amplified during the growing season. Although growth rates commonly are understood to reflect current temperatures, these results demonstrate a persistent effect of early-season temperatures, which should be considered in future growth models.
Apical dominance
Lateral shoot
Growing season
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Intact and decapitated 6-node shoots of Hygrophila sp. were grown aseptically immersed in liquid half-strength Knop's solution with microelements and 2% (w/v) sucrose (control medium), and in medium with 0.1 mg l−1 benzyladenine (BA). In intact shoots grown in control medium apical dominance suppressed outgrowth of the lateral buds; in decapitated shoots buds grew out at several of the most apical nodes, increasing in size acropetally. There was a lag in outgrowth of the bud at the most apical node, attributable to its initially smaller size. Lateral shoots grew out first at basal nodes of intact shoots in BA medium, decreasing in size acropetally; in decapitated shoots in BA medium lateral shoots of approximately equal size grew out at all nodes. Differential effects of decapitation and cytokinin treatment on lateral shoot outgrowth along the shoot could be interpreted by postulating a basipetally decreasing gradient of endogenous auxin concentration in the intact shoot. Application of 20 mg l−1 indoleacetic acid (IAA) in agar to decapitated shoots completely prevented bud outgrowth for at least 7 d in control medium, inhibiting it thereafter, and inhibited bud outgrowth in BA medium, thus supporting the hypothesis. Comparison of lateral shoot outgrowth in whole decapitated shoots and severed decapitated shoots (isolated nodes) lent no support to the alternative hypothesis that there might be an acropetally decreasing concentration gradient of a bud-promoting substance in the intact shoot, and demonstrated much greater lateral shoot growth in isolated nodes. The results emphasize important correlative relationships between the parts of a shoot with several nodes.
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Lateral shoot
Apical cell
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Vigorous shoots in chrysanthemums (Chrysanthemum morifolium) often develop from shoot tips (apical meristems with two leaf primordia) cultured in vitro following particle bombardment. The average fresh weight of regenerated shoots from a bombarded shoot tip of chrysanthemum ‘Jinba’ was 10 times more than that regenerated from unbombarded shoot tips. The average number of leaves per bombarded shoot tip was also more than that from an unbombarded shoot tip. The average number of leaves developing from a shoot tip increased with an increase in the amount of gold particles shot into the shoot tips. In addition, when the area destroyed in a shoot apical meristem (SAM) was varied by bombardment through nylon mesh with different pore sizes, the total number of leaves produced from each shoot tip increased with the size of the destroyed SAM area. Knowing the origin of these vigorous shoots, which may be from the bombarded meristem or from the lateral meristems, is important for the screening of transgenic plants. When the entire surface of a SAM was destroyed by bombardment, it was unable to rebuild itself; instead, lateral meristems were initiated at the base of the leaf primordia. Furthermore, the initiation of lateral meristems at the base of the leaf primordia was also observed in instances of restoration of the area of a partially destroyed SAM. This result indicates that vigorous lateral shoots initiate and develop from the bases of leaf primordia when SAMs are damaged to varying degrees. When leaf primordia-free shoot apical meristems (LP-free SAMs) were cultured after bombardment, vigorous shoots failed to develop from the wounded SAM; instead, the wounded LP-free SAMs regenerated a SAM by repairing the wounded areas and developed a non-vigorous single shoot. It was concluded the vigorous shoots do not participate in transgenic plant production because vigorous shoots arise from unbombarded lateral meristems. Finally, an effective and versatile method for transgenic plant production was established by combining micro-wound treatment on a SAM by bombardment and LP-free SAM culture to suppress the growth of vigorous lateral shoots after wounding.
Primordium
Lateral shoot
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SummaryUnfeathered maiden trees of apple Stark Earliest (syn. Scarlet Pimpernel) were pruned back in winter to a height of 70 cm. The following spring five shoots were allowed to grow out, the others being removed. When the leading shoots were about 12 cm. long the trees were sprayed once with various concentrations of GA, TIBA, CCC and B.9 (see below), other trees being left unsprayed as controls. Subsequent effects on shoot growth were analysed in terms of leaf number and internode length. Apical dominance was destroyed or greatly reduced by GA (200 p.p.m.), TIBA (200 p.p.m.) and CCC (5,000 p.p.m.) and these substances all increased leaf number on the lower shoots. B.9 (2,000 p.p.m.) had no effect on apical dominance. TIBA, CCC and B.9 reduced mean internode length on all shoots, whereas GA increased internode length on the lower shoots only.CCC caused only a temporary check to growth, but the growth-retarding effects of B.9 and TIBA persisted throughout the growing season. The possible mode of action of these growth regulators is discussed in relation to current theories of shoot growth and apical dominance.
Apical dominance
Dominance (genetics)
Lateral shoot
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Malus
Lateral shoot
Apical dominance
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The development of axillary buds, terminal buds, and the shoots extended from them was studied inHydrangea macrophylla. The upper and lower parts in a nonflower-bearing shoot are discernible; the preformed part of a shoot develops into the lower part and the neoformed part into the upper part (Zhou and Hare, 1988). These two part are formed by the different degrees of internode elongation at early and late phases during a growth season, respectively. Leaf pairs in the neoformed part of the shoot are initiated successively with a plastochron of 5–20 days after the bud burst in spring. The upper axillary buds are initiated at approximately the same intervals as those of leaf pairs, but 10–30 days later than their subtending leaves. Changes in numbers of leaf pairs and in lengths of successive axillary buds show a pattern similar to the changes in internode lengths of the shoot at the mature stage. The uppermost axillary buds of the flower-bearing shoot often begin extending into new lateral shoots when the flowering phase has ended. The secondary buds in terminal and lower axillary buds are initiated and developed in succession during the late phase of the growth season. Internode elongation seems to be important in determining the degrees of development of the axillary buds. Pattern of shoot elongation is suggested to be relatively primitive. Significances of apical dominance and environmental conditions to shoot development are discussed.
Elongation
Apical dominance
Lateral shoot
Bud
Dominance (genetics)
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The upper shoot on decapitated rose branches ( Rosa hybrids cv. Marimba) grows faster than lower shoots on the same branch. Transport of radioactive assimilates to the upper shoot is higher than to the lower ones. Darkening of the uppermost shoot resulted in the reduction of growth and I4 C‐assimilate accumulation in the darkened shoot as well as the promotion of growth and 14 C transport to the lower 2 shoots, thereby rendering dominance to the second shoot. Benzyladenine treatment to the uppermost shoot reversed the effect of darkening and restored the apical control of this shoot.
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Lateral shoot
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An investigation was made of the number of preformed organs in winter buds of 3‐year‐old reiterated complexes of the ‘Granny Smith’ cultivar. Winter bud content was studied with respect to bud position: terminal buds were compared on both long shoots and spurs according to branching order and shoot age, while axillary buds were compared between three zones (distal, median and proximal) along 1‐year‐old annual shoots in order 1. The percentage of winter buds that differentiated into inflorescences was determined and the flowers in each bud were counted for each bud category. The other organ categories considered were scales and leaf primordia. The results confirmed that a certain number of organs must be initiated before floral differentiation occurred. The minimum limit was estimated at about 15 organs on average, including scales. Total number of lateral organs formed was shown to vary with both bud position and meristem age, increasing from newly formed meristems to 1‐ and 2‐year‐old meristems on different shoot types. These differences in bud organogenesis depending on bud position, were consistent with the morphogenetic gradients observed in apple tree architecture. Axillary buds did not contain more than 15 organs on average and this low organogenetic activity of the meristems was related to a low number of flowers per bud. In contrast, the other bud categories contained more than 15 differentiated organs on average and a trade‐off was observed between leaf and flower primordia. The ratio between the number of leaf and flower primordia per bud varied with shoot type. When the terminal buds on long shoots and spurs were compared, those on long shoots showed more flowers and a higher ratio of leaf to flower primordia.
Primordium
Lateral shoot
Bud
Apical dominance
Organogenesis
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Citations (38)