NODE COUNTING IN AXILLARY BUDS OF NICOTIANA TABACUM CV. WISCONSIN 38, A DAY‐NEUTRAL PLANT
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Abstract:
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.Keywords:
Primordium
Apical dominance
Bud
Lateral shoot
Main stem
Apical dominance
Lateral shoot
Bud
Apex (geometry)
Dominance (genetics)
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Young, non- induced to flowering cuttings of the non-branching chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura) 'Iwanohakusen' were exposed to 30/20°C (day/night) to test whether the treatment inhibited differentiation of axillary buds from the shoot meristem. For comparison, comparable cuttings were grown at 20/15°C (control). Axillary bud initiation on plants, grown at 30/20°C, occurred, and the initials developed to a shell zone and a small mound of meristematic tissue in the leaf axils. However, they did not progress to the prophyll and leaf primordial stages as did the axillary buds of the control plants. Thus, the elevated temperature treatment did not affect the initiation of axillary buds, but it inhibited the meristem to differentiate further. Therefore, we consider that exposure to high temperature prevents differentiation of the prophyll and leaf primordium.
Primordium
Cutting
Lateral shoot
Bud
Apical dominance
Branching (polymer chemistry)
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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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This is a study of the vegetative growth of the banana plant, with special reference to the structure of the shoot apex, the origin of the leaf primordia and buds, and the growth of the leaf base into the pseudostem. The various regions in which intercalary growth contributes to the vegetative plant body are described. The anatomical structures observed are illustrated by photomicrographs. Binucleate cells are conspicuous in the leaf bases and in cells produced by intercalary men-stems. The formation of the air chambers which are characteristic of the mature leaf and of the septa, which are formed as persistent sheets of cells which bound these chambers, is described. The cell divisions which build the septa, and also those which cause the eccentric growth of the midrib are noted, and their proximity to adjacent vascular strands is stressed. Other marginal meristems build the lamina of the leaf. The function of the central apical meristem of the shoot is not to create a massive axis which grows in length, for this vegetative function is taken over by the lateral organs, the growth of which greatly overshadows that in the main axis. However, as the vegetative shoot grows older, its central mass of meristem does become progressively larger. Cell divisions in this central area are sparse, though sufficient to increase its bulk slowly, while the main organ-building and cell-multiplying functions are delegated to the lateral organs. This condition changes on flowering when a massive, true, erect stem forms. Axillary buds do not occur in the vegetative shoot, but adventitious buds appear in an anomalous situation. The vegetative shoot behaves as though there is an extremely strong apical dominance, which suppresses all buds and growth in the axis itself. But an elusive question is the mechanism which stimulates, or controls, the behaviour of so many dividing cells, distributed so widely, through so many discrete areas of cell division or intercalary meristematic activity. The frequent proximity of vascular strands, as probable sources of both nutrients and stimuli to cell division, is suggestive here.
Primordium
Lateral shoot
Apex (geometry)
Lamina
Vegetative reproduction
Apical dominance
Main stem
Vascular tissue
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Sumary: Higher plants develop species-specific architectures by continuously generating lateral structures such as leaves and flowers from the shoot apical meristem post-embryonically. Their primordia are generated with phyllotactic patterns of species-specific manner and develop autonomously from the shoot apical meristem. In addition, axillary shoots, which form in the axils of leaves develop autonomously from the main axis and affect the final architecture of a plant. The variations of different developmental patterns in these lateral structures give rise to a variety of plant morphology. In this review, we focus on molecular mechanisms that regulate development of lateral structures.
Primordium
Lateral shoot
Apical dominance
Apical cell
Phyllotaxis
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SummaryThe initiation of leaves and flowers by selected axillary buds of the glasshouse rose cultivar Sonia (syn. Sweet Promise) has been studied both while their extension growth was inhibited by apical dominance and after the inhibition had been removed at one of two times (“early” or “late”). Leaf initiation occurred during growth inhibition so that leaf primordia accumulated in the axillary buds. Flower initiation began, with both treatment times, only after removing apical dominance. Although the total number of leaf primordia formed before the flower was greater in plants of the “late” treatment, the axillary shoots produced in both treatments had similar numbers of leaves with expanded leaflets. Thus many leaf primordia of the “late” treatment plants became scales. The evidence suggests that flower initiation cannot begin while an axillary bud is subject to apical dominance, and that after its removal another factor results in the production of shoots with a relatively constant number of leaves with expanded leaflets.
Primordium
Apical dominance
Lateral shoot
Bud
Dominance (genetics)
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Primordium
Lateral shoot
Apical dominance
Bud
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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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