Flowering in tobacco: The course of floral induction under controlled conditions and in the field

Hopkinson, J.M.; Hannam, Rae V

doi:10.1071/ar9690279

Cited by 18 publications

(6 citation statements)

References 6 publications

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“…The acquisition of this state appears to be an inductive process in which a developmental signal acts on competent cells to bring about a specific state of determination (11,12). This inductive process in day-neutral tobacco is similar to that described for photoperiodic tobacco (13,14).…”

Section: Methodsmentioning

confidence: 82%

Floral determination in internode tissues of day-neutral tobacco first occurs many nodes below the apex

Singer¹,

McDaniel²

1987

Proc. Natl. Acad. Sci. U.S.A.

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The temporal and spatial patterns of floral determination in cultured internode segments of Nicotiana tabacum L. cv. Wisconsin 38 were investigated. Segments from internodes, when cultured on hormone-free medium, either produced some de novo floral shoots or produced only vegetative shoots. Segments that produced some floral shoots were considered to contain florally determined tissues. The first internode tissues to exhibit floral determination were located 24 nodes (about 15 cm) below the terminal meristem on plants that had 21 leaves of length :3 cm (i.e., plants of age 21). Since the terminal meristem was morphologically vegetative at this age, floral determination in internode tissues did not result from a signal emanating from floral structures. As the plant continued growing, internode tissues progressively higher on the main axis gained the capacity to produce de novo floral shoots in culture. These data indicate that the inductive signal which elicited the state offloral determination in internode tissues was active in the upper half of the plant beginning at about age 21.Determination is the stable commitment of a cell or group of cells to a developmental pathway. Determination for floral development occurs in both the terminal bud and axillary buds of day-neutral Nicotiana tabacum prior to morphological initiation of floral structures (1-3). Floral determination also occurs in internode tissues, since tissues from the inflorescence and the internodes just below the inflorescence are capable of forming de novo floral shoots in situ and in culture, whereas comparable tissues from more basal areas of flowering plants, as well as tissues from vegetative plants, produce only vegetative structures in culture (4, 5). A similar pattern of floral determination is observed in superficial cell layers excised and cultured from different positions on flowering day-neutral tobacco plants (6). Thus, floral determination in N. tabacum occurs both in buds and in internode tissues. Here we investigate whether floral determination occurs in internode tissues before or after the terminal bud becomes determined for floral development, and we establish the position of the internode tissues that first exhibit floral determination.We employ two assays for assessing floral determination in day-neutral tobacco. In the first, a bud is assayed by rooting the bud. When rooted, florally determined buds produce few nodes, along with a terminal flower, and this number of nodes is comparable to that produced by equivalent buds in situ (1, 3). In the second assay, cross-sectional segments of an internode are cultured on hormone-free medium. If some of the regenerated shoots formed on the segments from an internode are floral, the internode is considered to contain florally determined tissues. In previous work (3) employing the first assay, we established that the terminal bud became florally determined about the time that the plant had 21 leaves of length ¢a3 cm. This process of floral determination was cryptic, in that the me...

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Section: Methodsmentioning

confidence: 82%

Floral determination in internode tissues of day-neutral tobacco first occurs many nodes below the apex

Singer¹,

McDaniel²

1987

Proc. Natl. Acad. Sci. U.S.A.

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“…Although some changes in the cellular components in other zones ofthe meristem are also associated with this developmental transition period, they are generally not as dramatic and therefore, were not included in this study. The transition to full commitment to flowering is quite prolonged in Nicotiana species (Waterkeyn et al, 1965;Hopkinson and Hannam, 1969;Thomas et al, 1975), and this cultivar was observed to require at least 13 consecutive exposures to an inductive photoperiod for floral evocation to occur (Fig. 1, 2).…”

Section: • Controlmentioning

confidence: 99%

“…IN PLANTS of Nicotiana tabacum, the time of floral initiation is of considerable economic importance since leafnumber becomes limited to the number present at the time ofevocation (Bonnand, 1956(Bonnand, , 1959Hopkinson and Hannam, 1969;Thomas et al, 1975). It has been shown for some species that quantitative information on ultrastructural changes in cellular and organelle composition of the shoot apex as it progresses from the vegetative to reproductive stage of growth is useful in the development of a better understanding of the flowering process (Gifford and Stewart, 1965;Havelange and Bernier, 1974;Havelange, Bernier, and Jacqmard, 1974;Lin and Gifford, 1976;Auderset and Greppin, 1977;Havelange, 1980).…”

mentioning

confidence: 99%

“…Most of the studies on flowering physiology have typically used absolute and rapidly transforming photoperiodic species, e.g., Sinapis alba (Bernier, Bronchart and Kinet, 1970;Bernier et al, 1974;Havelange et al, 1974;Bodson, 1975), Xanthium strumarium (Jacqmard et al, 1976;Havelange, 1980), Chenopodium album (Gifford and Tepper, 1962;Gifford and Stewart, 1965;Gifford and Corson, 1971). The flue-cured cultivars of Nicotiana tabacum, however, exhibit a quantitative response to photoperiod, and for these plants the floral transition is not as rapid as in absolute species (Waterkeyn, Martens and Nitsch, 1965;Hopkinson and Hannam, 1969;Thomas et al, 1975). Stereological methods are currently available for accurate measurement of differences in the ultrastructural composition of cells in different parts ofthe shoot apex (Mauseth and Niklas, 1979;Mauseth, 1981aMauseth, , b, 1982.…”

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confidence: 99%

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Stereological Study of Ultrastructural Changes in the Shoot Apical Meristem of Nicotiana Tabacum During Floral Induction

Kanchanapoom

Thomas

1987

American J of Botany

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Shoot apices of a short‐day sensitive line of Nicotiana tabacum L. cv. NCTG‐22 have been examined by electron microscopy for ultrastructural changes which occurred in the central zone over a 17‐day period during the transition from vegetative to reproductive growth. Plants were grown in controlled‐environment chambers of the NCSU Phytotron and exposed to an inductive photoperiod after a 6‐wk juvenile phase. Ultrastructural changes were investigated from photomicrographs using a semi‐automatic stereological procedure and a microcomputer. After exposure to only one inductive cycle cell and nuclear cross sectional areas in short‐day plants were significantly larger than in long‐day controls. Subsequently, under short days cross sectional areas of cells, nuclei, vacuoles and proplastids decreased, while mitochondrial cross sectional area and relative volume increased during the course of the induction period. In induced apices as cross sectional areas and relative volumes of vacuoles and proplastids decreased, their profile numbers increased. The reduction in cross sectional areas of cells and most organelles was associated with an increase in rate of leaf initiation and size of the apical dome. The demand for sufficient energy input to maintain the surge in growth and activity preceding floral initiation was reflected by the significant increases in cross sectional area, profile numbers and density of the mitochondria population. Even though the transition period is quite long for Nicotiana, cells and organelles in the central zone were observed to progress through similar changes in morphology that are known to occur in Sinapis and Xanthium which exhibit a more rapid and absolute response to photo‐induction.

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“…More needs to be known about this phenomenon if carbon usage is to be predicted accurately.. The demand limitation, if it does exist, is presumably due to the strong apical dominance in tobacco and the lack of heavy accumulation of primordia on the stem apex (Hopkinson and Hannam 1969).…”

Section: Discussionmentioning

confidence: 99%

An Exploration of the Carbon Economy of the Tobacco Plant I. Inferences From a Simulation

Hackett¹

1973

Aust. Jnl. Of Bio. Sci.

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The question of whether photosynthesis may frequently be suppressed in the tobacco plant due to lack of demand for assimilates was examined using simulation techniques.The growth of the tobacco crop of Petrie et al. (1939) was first reproduced by use of growth analysis methods. Then the carbon estimated to be required for each day's growth and respiration was compared with that estimated to be potentially available, after allowing for leaf senescence. In making these calculations it was assumed (1) that all leaves were capable of photosynthesis at the nominated rate (20 mg CO2 dm-2 hr-i) for the whole period of light saturation, and (2) that light intensity was above saturation level for 10 hr daily, at least for the first 67 % of the growth period. (The grounds for these and other assumptions are discussed.) On this basis, the calculated potential photosynthetic capacity exceeded that required by 70-170%, depending on the stage of growth. Input values had to be varied to extreme limits to eliminate this excess.These calculations, which were intended to stimulate experiment on the carbon budget of tobacco, led to the following conclusions: that rates of photosynthesis of tobacco leaves may commonly be suppressed due to shortage of demand; that photosynthesis cannot therefore be reliably estimated for this crop from environmental analysis unless an effective ontogenetic routine is run concurrently; that accurate prediction of respiration rates will be less important for simulation purposes in tobacco than in the more common cases where the supply of assimilates is limiting; and that many aspects of the physiology of the tobacco plant might be better understood by treating the plant more as an integrated system than has been done previously.

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Flowering in tobacco: The course of floral induction under controlled conditions and in the field

Cited by 18 publications

References 6 publications

Floral determination in internode tissues of day-neutral tobacco first occurs many nodes below the apex

Floral determination in internode tissues of day-neutral tobacco first occurs many nodes below the apex

Stereological Study of Ultrastructural Changes in the Shoot Apical Meristem of Nicotiana Tabacum During Floral Induction

An Exploration of the Carbon Economy of the Tobacco Plant I. Inferences From a Simulation

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