In Vitro Culture and Plant Regeneration in Vicia faba subsp. Equina (var. Spring Blaze)

Explants of stem, leaves, roots, and cotyledons from etiolatedaxenically grown Vicia faba seedlings were cultured on a rangeof media. Shoot organogenesis was only obtained with nodal stemand cotyledonary node explants when cultured on MS medium with3% sucrose, 2.0 mg 1^–1 BAP and 02 mg 1^–1 NAA. Callusproliferation accompanied shoot organogenesis from nodal stemexplants. Successive subculture of nodal stem callus resultedin proliferation of regenerative callus which contained severalshoot bud initials. The capacity for shoot regeneration fromthis callus was maintained for 9 months. Histological studiesreveal de novo formation of meristematic centres in callus andtheir further development into bud primordia. High frequencyrooting of these adventitious shoots was obtained on half-strengthMS medium with 1.5% sucrose, 0.1 mg 1^–1 NAA and 0.5 mg1^–1 kinetin. Key words: Vicia faba, adventitious shoots, axillary shoots, de novomeristem formation, organogenesis, tissue culture     

The Carnation Succulent Plantlet -- A Stable Teratological Growth

Axillary buds of carnation (cv. Cerise Royalette) cultured invitro, frequently became ‘succulent’ plantlets,which proved to be a teratalogical stable type of growth. Agarconcentration (0.8–1.2 per cent) in the medium influencedthe type of development, and 0.05, 1 or 2 mg l^–1 of NAAin the medium did not change the results. The succulent plantletsdid not revert to normal growth when transferred to medium containingmore agar, which favoured normal plantlet development. Succulentexcised meristems developed mainly into succulent plantlets. A hypothesis is made that a rearrangement of the meristem occursin the first days of growth, the consequence of which is thesucculent plantlet, which is no longer influenced by agar concentrationin the medium. Carnation, Dianthus caryophyllus L. cv. Cerise Royalette, vegetative shoot meristem, agar effect, meristem organization     

Quantitative analysis of the combined effects of temperature, evaporative demand and light on leaf elongation rate in well-watered field and laboratory-grown maize plants

The respective effects of meristem temperature, vapour pressuredeficit (VPD) and photosynthetic photon flux density (PPFD)on leaf elongation rate (LER) of maize, in the absence of waterdeficit in the soil have been quantified. This analysis wascarried out in a series of field experiments in northern andsouthern France over several seasons and years, and in growthchamber experiments. LER was measured with 10 min steps, togetherwith meristem temperature, VPD and PPFD at leaf level in threetypes of experiments: in growth chamber experiments with stepsin PPFD or VPD at constant meristem temperature, in growth chamberexperiments with several combinations of constant, but contrasting,PPFDs, VPDs and meristem temperatures, and in the field withfluctuating conditions, (i) When evaporative demand was low(night or day with low air VPD), LER was only linked to meristemtemperature, regardless of other climatic conditions, (ii) Lighthad no effect per se on LER in the range from 0 to 1500 molm^–2 s^–1 for time-scales longer than 2 h, providedthat its indirect effects on meristem temperature and on evaporativedemand were corrected (in the growth chamber) or taken intoaccount (in the field), and provided that cumulated PPFD overa weekly time-scale was compatible with field conditions, (iii)Evaporative demand sensed by growing leaves, as estimated bymeristem-to-air vapour pressure difference, markedly affectedLER in the range from 1–4 kPa, at all time-scales understudy, with a unique relationship in the growth chamber (constantconditions) and in the field (fluctuating conditions). Thiseffect was only observed when PPFD was high enough for stomatato open. The negative effect of evaporative demand on LER wasprobably not due to long distance root-to-shoot signalling,since soil was wet, calculated root water potential remainedclose to 0 MPa and concentration of ABA in the xylem sap wasvery low. Therefore, it is proposed to model maize LER witha two-step process, involving the calculation of the maximumLER at a given meristem temperature and then the calculationof the reduction in LER due to evaporative demand. Joint analysisof the whole set of data by using the two equations yieldeda r² of 0.75. This two-step process would be more accurate thanthe provision of LER from temperature only in cases where airVPD frequently exceeds 2 kPa. Key words: Leaf growth, light, evaporative demand, temperature, thermal time, water deficit, ABA, Zea mays L.     

Nuclear and Cell Sizes in Different Regions of Root Meristems of Zea mays L.

Nuclear volumes and cell areas were determined for seven regionsof the meristem of roots of Zea mays. Roots were fixed in 10per cent neutral buffered formalin, in 3 per cent glutaraldehydeor in acetic acid/alcohol; they were prepared as sections oralls were teased apart. Mean volumes of interphase nuclei weresimilar in all regions of the root except the vascular tissueof the stele. Mean nuclear volumes and the overall range ofvolumes were similar in sub-populations of cells with differentproportions of G¹, S and G² cells, e.g. in row I of root capinitials, whose cells lack a G¹ phase, and in quiescent centrecells, which are mainly in G¹. Nuclear volume does not appearto be closely correlated with DNA content. Nuclear volumes covereda 6 to 12-fold range within a meristem and even within specificregions, in which cells are part of the same cell lineages,there was a 4- to 9-fold range. Nuclear volumes were comparedin sister cells in rows I and II of the root cap initials. In10 per cent of the pairs, sister nuclei had identical volumes;the other pain had different volumes and mean difference was68 µm³. Mechanisms by which this variability could begenerated are discussed, particularly asymmetry, at mitoses,of factors that regulate nuclear growth. Zea mays L., nuclear volume, cell size, root mcristem, DNA content, mitosis     

Developmental Responses to Drought and Abscisic Acid in Sunflower Roots: 2. MITOTIC ACTIVITY

Mitotic activity was studied in the root apices of aeroponicallygrown sunflower seedlings (Helianthus annum L. var. RussianGiant) which were draughted or treated with abscisic acid (ABA)over a 7 d period. Labelling index (LI) and mitotic index (MI)were scored from autoradiographs of median longitudinal sectionsof [³H] methyl-thymidine treated root apices. Both drought stressand ABA-treatment (at a concentration of 10^–2 mol m^–3inhibited DNA synthesis and mitosis within the first 6 h oftreatment. The depression of mitotic activity was first evidentin the proximal regions of the meristem (1000–1500 µmfrom the cap junction). This was followed by a general depressionof mitotic activity throughout the meristem which was, in turn,followed by a partial recovery of mitotic activity in the distalregions of the meristem. The beginning of this partial recoverywas concurrent with the activation of the quiescent centre (QC).Treatment with lower concentrations of ABA (10^–3 mol m^–3and 10^–4 mol m^–3) also inhibited mitotic activity.Exogenous supplements of sucrose to the plant did not alleviatethe inhibition of mitotic activity by drought or ABA. Thesefindings support the hypothesis that ABA mediates drought-inducedchanges in the primary development of sunflower roots. Key words: Abscisic acid, drought, mitotic activity     

Localization of Nucleic Acid Synthesis in Root Meristems

Adenine-8-C1¹⁴ was supplied to roots of Vicia faba and Alliumascalonicum and its incorporation into DNA was studied fromautoradiographs of hydrolysed sections. These roots have a quiescentcentre to the meristem where the cells do not synthesize DNAand probably, therefore, play no part in the construction ofthe root. The boundary between the quiescent centre and thecentral cap initials is clearly denned and this suggests thatthere is as little cell interchange between the histogens asthere is in roots with visibly discrete histogens.     

Evidence against involvement of circadian floral rhythm in the critical daylength measurement in Lemna gibba G3

Using the min-LD method, light requirements of the L1- and L2-phasesof L. gibba G3 were found to be satisfied by only 5 min illuminationgiven respectively from CT 0:00 to 0:05 and from CT 11:55 to12:00. This rigorous time sense was displayed without any alterationeven in the presence of iron reagents, e.g., 10^–5 M o-phenanthroline,10^–5M,'-dipyridyl and 10–6 M kinetin, which completely eliminatedcircadian rhythmicity in reproductive (flower production) aswell as vegetative (frond production) response to a light pulsescanning a continuous dark period. Circadian rhythms of metabolicactivities, e.g., active K⁺ ion uptake and respiratory CO₂ output,were not changed at all by the iron reagents. These and relevantresults suggested that in this long-day duckweed, the circadianoscillator, probably located in the meristem and sensitive toiron deficiency, only modulates the frond and flower productionin the meristem and is not related to the critical daylengthmeasurement. (Received December 18, 1978; )     

In Vitro Micropropagation of Delphinium malabaricum (Huth) Munz.--a Rare Species

A micropropagation technique was developed for Delphinium malabaricumusing nodes from inflorescence stalks Maximum shoot proliferationwas obtained on Murashige and Skoog's medium supplemented with2-1P (10 mg l^–1) and inositol (100 mg l^–1) Fromthe sixth passage onwards, shoots could be multiplied by omissionof inositol and reduction of 2-1P (0.5 mg l^–1) concentrationBest rooting response was obtained with a 24-h pulse treatmentof shoots with 0.5 mg I^–1 IBA in the dark, transfer oftreated shoots to hormone-free half-strength MS medium and incubationunder 24-h light. Regenerated plants were established successfullyin the field Cytological examination of root tips of in vitroand control plants showed identical chromosome number (2n =16) Delphinium malabaricum (Huth) Munz, micropropagation, tissue culture, rare plant     

Scanning Electron Microscope Studies of Multiple Shoot Production by Meristem Tip Cultures of Solarium x curtilobum

A meristem tip culture isolated from Solatium x curtilobum cv.Mallku produced a limited amount of callus at the cut surfaceof the explant when cultured on Murashige and Skoog medium containing1 mg dm³ 6--{dimethylallylamino)purine and O.01 mg dm³ naphthaleneacetic acid. A single sheet of cuticle-like material develops on localizedregions of the callus surface and the cells beneath it decreasein mean cell size. These meristematic centres develop into fullyorganized shoot meristems, and each will grow out into a leafyshoot when the culture is transferred to growth medium containingo.1 mg dm³ gibberellic acid (GA₃) as the only growth hormone.This system has considerable value in the rapid clonal propogationof Solanum species, since as many as fifty shoots can be producedfrom a single meristem tip culture.     

Micropropagation of Indian Rosewood by Tissue Culture

Multiple shoots were induced on excised hypocotyl segments andshoot tips of in vitro germinated seedlings of Indian rosewood(Dalbergia latifolia) on Murashige and Skoog's medium supplementedwith cytokinins and auxins. Roots were induced when individualshoots were treated first with half strength MS medium supplementedwith NAA, IAA and IBA (1 mg 1^–1 each) and subsequentlytransferred to hormone-free half-strength MS medium. The plantletswere then transferred to pots and grown in the greenhouse. Dalbergia latifolia, micropropagation, tissue culture, clonal propagation     

Distribution of Radioactivity from Exogenously Supplied [1-14C]Indol-3-yl-acetic Acid and [3, 4-3H (N)] Gibberellin A, in Geotropically-stimulated Picea abies (L.) Karst. Roots

The distribution of exogenously-supplied radioactive labelledindol-3-yl-acetic acid (IAA) and gibberellin A₁ (GA₁) in geotropicallystimulated roots of Norway spruce (Picea abies (L.) Karst.)has been demonstrated. Seedlings were positioned with theirroot tips in 2.1 x 10^–6 M [¹⁴C]IAA or 1.3 x 10^–8m ³H-GA₁ for 4 and 20 h, respectively. After geotropic stimulationfor 90 min in the horizontal position the root tips were cutlongitudinally in 50 µm thick sections, using a freeze-microtome.The radioactivity in the ¹⁴C-IAA treated roots occurred in higherconcentration in the lower than in the upper halves (ratio 1.25:1). A similar trend was observed in the [³H]GA₁-treated rootswhere the ratio lower: upper halves was 2.04: 1. The ratio ofradioactivity in right and left halves of vertical roots wasapproximately the same in roots supplied with [¹⁴C]IAA and [³H]GA₁(1.09: 1). The supplied radioactive compounds were analysed chromatographicallyafter extraction in methanol of 6 mm apical root segments. Onlya small fraction (7–8 per cent) of the supplied [¹⁴C]IAAwas revealed unchanged in the segments. The major part of thechromatographed, labelled compound has not been identified,but on basis of its R_F value it is suggested that it may beindol-3-acetyl-aspartic acid (IAAasp). The chromatographic analysis of the [³H]GA,-treated segmentsshowed that only small fractions of this gibberellin has beenconverted to other compounds. These results have been discussed and correlated with knowledgeof plant growth regulators and their participation in root geotropism. Picea abies, spruce, geotropism, gibberellin A₁, indol-3-yl-acetic acid, growth regulators, redistribution in roots     

Zinc-induced Vacuolation in Root Meristematic Cells of Cereals

In the absence of Zn, vacuolar volume fractions of root meristematiccells of Secale cereale L. cv. K2, Triticum aestivum L. cv.Chinese Spring and Oryza sativa L. cv. IR34 were 5.64 x 10^–2,2.17 x 10^–2 and 1.63 x 10^–2 µm³ vacuole µm^–3tissue, respectively. A 4-d exposure to a subtoxic concentrationof zine (0.2 µg Zn cm^–3) induced a 2.93-fold anda 6.78-fold increase in the total vacuolar volume fraction inOryza and Triticum, respectively, whereas no significant increasewas observed for Secale. It is proposed that this Zn-inducedvacuolation represents a compartmentalization mechanism. Theinitial total vacuolar volume fraction in Secale was greaterthan that for Oryza and Triticum and this may enable compartmentalizationof the metal soon after the onset of treatment so reducing itscytotoxic effects. These findings are similar to those observedin contrasting cultivars of Festuca rubra L. Triticum aestivum L, Secale cereale L, Oryza sativa L, zinc, root meristem, vacuolation     

A Method for in Vitro Storage of Lolium multiflorum Lam

A means of storing Lolium multiflorum Lam. stock plants in vitrohas been developed over a period of three years. Variousexplantsand cultureconditions were examined. Shoot tips 0.3–0.9mm long were found to be best for establishing storage culturesbecause they gave a high yield of plantlets in culture and importantpathogens are eliminated. For sub-culturing, after each annualcycle of storage at 2–4 °C, shoot tips, tiller buds,tiller bases and nodes can be used. Tiller buds were most abundantand best for increasing the number of stored plantlets whennecessary. There was no advantage of including an auxin in theculture medium for shoot tips and Murashige and Skoog's mediumwith 0.2 mg l^–1 kinetin has been adopted for initiating,sub-culturing and storing cultures. The optimum temperaturerange for regenerating plantlets was 20–25 °C. Lightwas necessary for a high rate of plantlet regeneration and lightquality and intensity affected their growth. Lolium multiflorum Lam., ryegrass, storage in vitro, tissue culture     

Organelle DNA Synthesis in the Quiescent centre of Arabidopsis thaliana (Col.)

The behaviour of cell nuclei and organelle nucleoids (organellenuclei) was studied in the root apical meristem of 3-d-old seedlingsof Arabidopsis thaliana (Col.). Samples were embedded in Technovit7100 resin, cut into thin sections and stained with 4'-6-diamidino-2-phenylindole(DAPI) for observation of DNA. DNA synthesis in cell nucleiand organelle nucleoids was investigated using the incorporationof [³H] thymidine or 5-bromo-2'-deoxyuridine (BrdU). Incorporated[³H] thymidine and BrdU were detected by microautoradiographyor immunofiuorescence microscopy, respectively. Central cellsand cells just above the central cells of the quiescent centre(QC) showed an extremely low activity of DNA synthesis. However,DNA synthesis occurred in at least one organelle nucleoid ofall cells in the QC within 24 h. This suggests the cells inthe QC are quiescent with regard to nuclear DNA synthesis, butnot with regard to the organelle nucleoids. Key words: Arabidopsis thaliana, quiescent centre, root apical meristem, mitochondrial nucleoid (nuclei), plastid nucleoid (nuclei)     

Ion Imbalance in Capsicum annum scarbrous diminutive a Wilty Mutant of pepper: II.RUBIDIUM FLUX

Root tips of the wilty pepper mutant scarbrous diminutive accumulateless rubidium than those of the normal genotype. This phenomenonwas evident in root tips excised from plants maintained for2 d in CaSO₄ solution (low salt plants), especially in the lowerexternal concentration range (0.1– 1.0 mM) of RbCl. Theefflux rate of Rb⁺ from mutant root tips was twice as high asin normal root tips. These results indicate that the ability of the mutant rootsto absorb and accumulate Rb⁺ and K⁺ is impaired. This defectcould be a consequence of either an impaired Na⁺/K⁺ carriersystem, or increased leakiness of mutant membranes, or both. The fact that the normal roots can accumulate Rb⁺ much fasterthan mutant roots supports the first alternative, i.e. thatthe high affinity carrier system was impaired in the mutantroots. However, the higher efflux rate of Rb⁺ from the mutantroots suggests that membrane leakiness was also affected.     

Ochna pulchra Hook: Leaf Growth and Development Related to Photosynthetic Activity

Ochna pulchra Hook. is a deciduous broad-leaved tree in theMixed Bushveld vegetation of the Northern Transvaal. The growthand development of leaves taken from trees in the field werestudied from a stage shortly before bud break, in late spring,until they were fully expanded and at the peak of photosyntheticactivity. Leaf area was measured by photographing the leaf against a transparentmm² grid. Finally a constant relationship between leaf area(A) and the linear dimension of length (L) and breadth (B) wasestablished: A = b x LB, where coefficient b = 0.72. Transverse sections of the lamina of the youngest leaves showeda five-layered plate meristem with a few functional conductingelements in the midrib. During further leaf development, celldivision was followed by means of autoradiography using [³H]thymidine.It was most active during the week after bud break. Leaf cell increment following on cell division made the majorcontribution to leaf growth resulting in a lamina that was atleast 90% expanded 4 weeks after bud break. The histologicalchanges accompanying cell division were observed using lightand electron microscopy. Even in late stages of leaf development mature and differentiatingstomata occurred together, limited to the abaxial epidermisand the midrib. Scanning electron microscopy showed stomataldistribution, their increasing density and gradual opening.The structure of these sunken stomata could reduce the outwarddiffusion of water vapour and increase the diffusion resistanceto carbon dioxide. Carbon assimilation rates of the developing leaves were measuredusing an IRGA (infra-red gas analyser) and their chlorophyllvalues were calculated. Photosynthesis was first measured amonth after bud break when the leaves were fully expanded, over50 % of the stomata exposed and leaf mesophyll tissue differentiatedwith mature chloroplasts. Net photosynthetic rates and chlorophyllvalues peaked 1 month later. Ochna pulchra Hook., photosynthesis, leaf development, leaf area, stomata, chlorophyll, savanna     

THE STRUCTURE AND DISTRIBUTION OF PERIPHERAL CILIATED RECEPTORS IN THE BIVALVE MOLLUSCS DONAX SERRA AND D. SORDIDUS

The siphons and mantle edge of Donax serra and D. sordidus possesstwo types of ciliated sensory receptor. Type 1 has > 7 ciliawith an exposed length of 0.7–2.4 µm. Type II hasfewer cilia (2–5) which are 2–6 µm long. Athird type (Type III) described from the tips of the tentaclesof the siphon and mantle edge of D. sordidus, possesses twotufts of cilia which are 12 µm long. All three receptortypes appear to be primary receptors. Estimates of abundanceshow that receptors are most numerous on the tips of the siphontentacles (9.75 x 10³. mm^–2), and it is suggested thatthese receptors function as chemoreceptors. (Received 11 May 1983;     

A Maize Mutant with an Altered Vascular Pattern

A recessive maize mutant with disrupted seedling developmentwas isolated following transpositional mutagenesis with Mutator.This mutant, initially identified during germination on thebasis of abnormal growth of the scutellar node, was designatedlsn1 (l arge s cutellar n ode). The mutant seedling exhibitsan enlarged primary root with a longitudinal groove and multipleseparate root tips. The mutant root is shorter than normal,because of defective cell elongation, and lacks lateral roots.The mutant plant shows defective leaves and reduced internodeelongation. Histological analyses on primary root, shoot, scutellarnode and juvenile leaves revealed a series of defects, all relatedto an irregular differentiation of vascular elements. In addition,in situ hybridization of mutant leaves demonstrates an abnormalpattern of expression of Knotted-1, a marker of meristem function.The presence of multiple roots fused together can be interpretedas suppression of the negative control responsible for the differentiationof only one root primordium. Therefore, the data obtained onseedlings of lsn1 point to a relationship between meristem activity,vascular differentiation and auxin polar transport, and mayallow the identification of a gene which is active during embryogenesis.Copyright2000 Annals of Botany Company Auxin, defective seedling, maize, meristem activity, vascular differentiation, Zea mays.     

Development and Control of the Number of Flowers per Node in Pisum sativum L.

Non-dormant flower initials are laid down in the axils of successiveleaf initials as they are formed by the apical meristem of Pisumsativum L. In cultivars with a maximum capability of two flowersper raceme, the undeveloped flower meristem divides into twoportions. One forms the first flower and the other either developsinto a small protrusion on one side of the first flower or becomesthe second flower, depending on the prevailing environment.Flower development in conditions favouring single-flowered racemeswas advanced by one plastochron. Variation in the number offlowers per raceme occurs between cultivars and between environments.The number of double flowers formed was favoured by higher lightintensity (120 Js^–1 m^–2) and carbon dioxide concentration(330 µ11^–) and lower temperature (15°C). Incultivars producing more than two flowers per raceme, lowerlight intensity (60 Js^–1 m^–2) plus higher temperature(20°C) increased the mean number of flowers per raceme.Soluble sugar levels in all varieties were higher (36.05 mgeq glucose g^–1 fresh weight) in the low temperature/highlight environment than the high temperature/low light environment(14.80 mg eq glucose g^–1 fresh weight). The flowering potential and stability of 13 cultivars have beenassessed in controlled environment and in sowing date trialsin the field. A stable variety, which consistently producedtwo flowers per raceme, was identified in controlled environmentand its stability was maintained in field trials. A linear regressionof stability of flower number in the field on stability in controlledenvironment accounted for 89.6 per cent of the variance (P<5per cent), but the flowering potential in a sowing date experimentwas not related to temperature or radiation intensity.     

Effects of Light on the Production and Degradation of Caffeine in Camellia sinensis L. Seedlings

Light enhanced the growth of tea seedlings but the amount ofcaffeine produced in light was almost identical to that in theshade, indicating that more synthesis and/or less degradationof caffeine Occur(s) in shaded seedlings. Administering [N¹-methyl-¹⁴C]-caffeinecaffeine to tea shoot tips showed that light promotes the degradationof caffeine only slightly. (Received January 28, 1985; Accepted February 25, 1985)