Floral activity in solutions of deoxyribonucleic Acid extracted from tobacco stems

For Nicotiana tabacum cv. Wis. 38 plants, the capabilities of solutions containing DNA, extracted from either homogenates of stems in a floral state or nuclei of stems in a vegetative state, to effect flowering of vegetative plants have been studied. Previous work indicates that the DNA from homogenates of stems in a floral state is mainly nuclear. If DNA solutions are supplied to axillary buds of vegetative plants and if the axillary buds are defoliated every 4th day for 12 days, the buds supplied a solution of DNA from stems in a floral state initiate flowers under noninductive conditions, and the buds supplied a solution of DNA from stems in a vegetative state remain vegetative. Heating and rapidly cooling a solution of DNA from stems in a floral state enhances its floral activity. Heating and cooling a DNA solution also results in novel flowers showing up in many treated plants. Novel flowers are more striking in the offspring than in the parents. The capabilities of heated-cooled DNA solution to initiate flowers in noninductive conditions and to cause novel flowers are eliminated completely by treating (before heating and cooling) the DNA solution with deoxyribonuclease. Heated-cooled solutions of DNA extracted from nuclei of either vegetative stems or vegetative leaves contain no floral activity.     

Flower Formation in Excised Tobacco Stem Segments: III. Deoxyribonucleic Acid Content in Stem Tissue of Vegetative and Flowering Tobacco Plants

A method has been developed that extracts DNA from stem tissue of flowering tobacco plants, Nicotiana tabacum cv. Wis. 38. The DNA content of stem tissue from a flowering tobacco plant is correlated with its capacity to flower in vitro. Stem segments known to form 100% floral buds contain 10 times more DNA per gram fresh weight than segments that form 5% floral buds and 95% vegetative buds, and in the uppermost 28 centimeters of flowering tobacco plant stems the DNA content decreases roughly in parallel with the floral gradient.     

Occurrence of the plant growth regulator jasmonic acid in plants

The natural occurrence of jasmonic acid and its methyl ester in plants has been studied using different methods such as GC, GC-MS, HPLC, radioimmunoassay, and bioassay. Jasmonic acid was detected in several Leguminosae plants and a number of species belonging to nine other Angiospermae families. Highest amounts occurred in fruit parts, especially the immature pericarp, but it was found also in flowers and vegetative plant parts, e.g. leaves, stems, and germs. Young apple fruits contain both jasmonic acid and methyl jasmonate, and in Douglas fir, the only Gymnospermae species studied, only the methyl ester could be detected. Jasmonic acid is discussed as an endogenous plant growth regulator widely distributed in higher plants.     

Characterization of the most rapidly renaturing sequences in mouse main-band DNA

The most rapidly renaturing sequences in the main-band DNA of Mus musculus, isolated on hydroxyapatite, are found to consist of two discrete families: a presumed “foldback” DNA fraction and a fraction renaturing bimolecularly. The latter family, which we call “main-band hydroxyapatite-isolated rapidly renaturing DNA”, has a kinetic complexity about an order of magnitude greater than that of mouse satellite DNA. It shows about twice as much mismatching as renatured mouse satellite, as judged by its thermal denaturation curve. In situ hybridization localizes the sequences to all chromosomes in the mouse karyotype, and to at least several regions of each chromosome. The in situ result and solution hybridization studies eliminate the possibility that the main-band rapidly renaturing DNA is composed of mouse satellite sequences attached to sequences of higher buoyant density. Nuelease S₁ digestion experiments disclose that even at low molecular weight there are unrenatured “tails” attached to the rapidly renaturing sequences. When the main-band DNA fragment size is increased the amount of rapidly renaturing sequences remains constant, but the amount of attached tails of unrenatured DNA increases as judged by S₁ nuclease digestibility, hyperchromicity and buoyant density. It is concluded that at least 5% of the mouse genome is composed of segments of the rapidly renaturing sequences averaging about 1500 base pairs, alternating with segments of more complex DNA averaging about 2200 base pairs. This interspersion of sequences is compared to that found in several other organisms. The properties of the foldback DNA are similarly investigated as a function of DNA fragment size.     

DNA reassociation kinetics and chromosome structure in the crabs Cancer borealis and Libinia emarginata

DNA reassociation kinetics have been partly elucidated for the higher crabs C. borealis and L. emarginata, using calf thymus DNA as a standard. These crabs contain no detectable repeated DNA in the approximate multiplicity frequency range 2-100 copies, which is unusual for invertebrate DNAs. Each species contains a component renaturing at an intermediate rate, and also a very rapidly renaturing fraction. The very rapidly renaturing fraction is considerably larger than the cesium chloride-resolvable satellites of each species. The fraction reassociating at an intermediate rate includes sequences with a reiteration frequency of up to 9.0 X 10(4) copies. This is unusually high for invertebrate DNAs. The nearly exact correlation between kinetic complexity and independently determined haploid genome size leads to the conclusion that the most slowly renaturing sequences of both crab species are present only once per haploid genome. Therefore the chromatids of these species are uninemic structures, and there has been no detectable occurrence of polyploid speciation in the recent evolutionary history of either species.     

The small-scale spatial distribution of male and female plants

Summary There are many reports of dioecious flowering plants with positive spatial association of gender, such that males and females tend to occur at different sites. This pattern has been interpreted as demonstrating environmenal heterogeneity, the two sexes having different habitat preferences. However, it is not clear: (a) to what extent the literature reflects the greater likelihood of publishing striking positive results; and (b) whether the association of stems of like gender within habitats is caused by differences in microhabitat preference rather than by vegetative ramification. We surveyed natural populations of ten sexually heteromorphic species in southern Quebec, and found that five showed positive association and four showed no association between the genders. With one exception (Silene cucubalus) these results appeared to reflect the presence or absence of vegetative ramification. We conclude that the demonstration of spatial association cannot be used to infer the existence of microenvironmental heterogeneity except in species with no capacity for vegetative ramification. The tenth species, Silene alba, showed negative association, with an excess of neighbouring pairs of unlike gender, but we were unable to reproduce this phenomenon experimentally.     

Disturbance in the allocation of carbohydrates to regenerative organs in transgenic Nicotiana tabacum L

Transgenic tobacco (Nicotiana tabacum L, cv. SR-1) expressing mannitol 1-phosphate dehydrogenase, MTLD, in chloroplasts and myo-inositol O-methyltransferase, IMT1, in the cytosol after crossing of lines which expressed these foreign genes separately has been analysed. Plants expressing both enzymes accumulated mannitol and D-ononitol in amounts comparable to those following single gene transfer and showed phenotypically normal growth during the vegetative stage. Induction of flowering for transgenovar and wild-type occurred at the same time, but during flowering the phenotype of the transformed plants changed. Compared to wild-type, transgenic plants were characterized by curled, smaller upper leaves and elongated stems during flowering; incomplete development of flower buds with shorter sepals and pedicels resulted in increased abortion. Flowers completing development were normal. The vegetative biomass of the transformed plants was slightly higher than that of wild-type. Concentrations of soluble sugars and potassium were lower than in wild-type only in the apical parts of the transgenic plants. Both enzymes, under control of the CaMV 35S promoter, promoted accumulation of mannitol and D-ononitol in the youngest leaves close to the vegetative meristem and in flowers, suggesting that their presence could signal lower sink demand leading to a decrease in carbon import to flowers and developing seed capsules. The interpretation here is that increases of inert carbohydrates in developing sinks interfere with metabolism, such as respiration or glycolysis. This interference may be less significant in source tissues during vegetative growth than in sink tissues during seed development.     

The rates of shoot and root growth in intact plants of pea mutants in leaf morphology

Isogenic lines of pea (Pisum sativum L.) with the genetically determined changes in leaf morphology, afila (af) and tendril-less (tl), were used to study the relationship between shoot and root growth rates. The time-course of shoot and root growth was followed during the pre-floral period in the intact plants grown under similar conditions. The af mutation produced afila leaves without leaflets, whereas in the case of the tl mutations, tendrils were substituted with leaflets, and acacia-like leaves were developed. Due to the changes in leaf morphology caused by these mutations, pea genotypes differed in leaf area: starting from day 7, the leaf area was lower in the af plants and larger in the tl plants as compared to the wild-type plants. Such divergence was amplified in the course of plant development and reached its maximum immediately before the transition to flowering. Plants of isogenic lines did not notably differ in stem surface areas. In spite of significant difference in total leaf area, the wild type and tl plants did not differ in leaf dry weight. Starting from leaf 9, the af plants lagged behind two leaflet-bearing genotypes (wild type and tl) in leaf dry weight, whereas stem dry weight was similar in the wild type and tl forms and slightly lower in the af plants. Root dry weights were practically similar in the wild type and tl plants until flowering. The reduction of leaf area in the af plants drastically reduced root dry weight. In other words, the latter index was related to the total weight and total area of leaves and stems. The correlation analysis demonstrated an extremely low relationship between leaf and stem area and dry weight and those of roots early in plant development (when plants develop five to seven leaves). Later, immediately before flowering (nine to eleven leaves), root weight was positively related to leaf weight and area; however, stem area and root weight did not correlate. Thus, in three genotypes (wild type, af, and tl), at the end of their vegetative growth phase, leaf and root biomass accumulated in proportion, independently of leaf area expansion.     

Sequence heterogeneity in kinetoplast DNA: Reassociation kinetics

Melting and reannealing of purified kinetoplast DNA (kDNA) from Crithidia fasciculata, Trypanosoma mega, and T. brucei have been studied with an automated optical system. The slow reassociation rate of trypanosome kDNA is due neither to the formation of hyperpolymers nor to mispairing of bases and certainly reflects extensive sequence heterogeneity. Simulation of the reassociation kinetics indicates that the kDNA comprises essentially two kinetic components: a fast renaturing component which might be a common sequence present in all the minicircles and a slow renaturing component which is responsible for minicircle heterogeneity. The rapidly renaturing component is more abundant in Crithidia than in trypanosomes.     

Occurrence of the plant growth regulator jasmonic acid in plants

The natural occurrence of jasmonic acid and its methyl ester in plants has been studied using different methods such as GC, GC-MS, HPLC, radioimmunoassay, and bioassay. Jasmonic acid was detected in several Leguminosae plants and a number of species belonging to nine other Angiospermae families. Highest amounts occurred in fruit parts, especially the immature pericarp, but it was found also in flowers and vegetative plant parts, e.g. leaves, stems, and germs. Young apple fruits contain both jasmonic acid and methyl jasmonate, and in Douglas fir, the only Gymnospermae species studied, only the methyl ester could be detected. Jasmonic acid is discussed as an endogenous plant growth regulator widely distributed in higher plants.     

A yeast mitotic activator sensitises the shoot apical meristem to become floral in day-neutral tobacco

True day-neutral (DN) plants flower regardless of day-length and yet they flower at characteristic stages. DN Nicotiana tabacum cv. Samsun, makes about forty nodes before flowering. The question still persists whether flowering starts because leaves become physiologically able to export sufficient floral stimulus or the shoot apical meristem (SAM) acquires developmental competence to interpret its arrival. This question was addressed using tobacco expressing the Schizosaccharomyces pombe cell cycle gene, Spcdc25, as a tool. Spcdc25 expression induces early flowering and we tested a hypothesis that this phenotype arises because of premature floral competence of the SAM. Scions of vegetative Spcdc25 plants were grafted onto stocks of vegetative WT together with converse grafts and flowering onset followed (as the time since sowing and number of leaves formed till flowering). Spcdc25 plants flowered significantly earlier with fewer leaves, and, unlike WT, also formed flowers from axillary buds. Scions from vegetative Spcdc25 plants also flowered precociously when grafted to vegetative WT stocks. However, in a WT scion to Spcdc25 stock, the plants flowered at the same time as WT. SAMs from young vegetative Spcdc25 plants were elongated (increase in SAM convexity determined by tracing a circumference of SAM sections) with a pronounced meristem surface cell layers compared with WT. Presumably, Spcdc25 SAMs were competent for flowering earlier than WT and responded to florigenic signal produced even in young vegetative WT plants. Precocious reproductive competence in Spcdc25 SAMs comprised a pronounced mantle, a trait of prefloral SAMs. Hence, we propose that true DN plants export florigenic signal since early developmental stages but the SAM has to acquire competence to respond to the floral stimulus.     

Shifting season of fire and its interaction with fire severity: Impacts on reproductive effort in resprouting plants

Fire regimes shape plant communities but are shifting with changing climate. More frequent fires of increasing intensity are burning across a broader range of seasons. Despite this, impacts that changes in fire season have on plant populations, or how they interact with other fire regime elements, are still relatively understudied. We asked (a) how does the season of fire affect plant vigor, including vegetative growth and flowering after a fire event, and (b) do different functional resprouting groups respond differently to the effects of season of fire? We sampled a total of 887 plants across 36 sites using a space‐for‐time design to assess resprouting vigor and reproductive output for five plant species. Sites represented either a spring or autumn burn, aged one to three years old. Season of fire had the clearest impacts on flowering in Lambertia formosa with a 152% increase in the number of plants flowering and a 45% increase in number of flowers per plant after autumn compared with spring fires. There were also season × severity interactions for total flowers produced for Leptospermum polygalifolium and L. trinervium with both species producing greater flowering in autumn, but only after lower severity fires. Severity of fire was a more important driver in vegetative growth than fire season. Season of fire impacts have previously been seen as synonymous with the effects of fire severity; however, we found that fire season and severity can have clear and independent, as well as interacting, impacts on post‐fire vegetative growth and reproductive response of resprouting species. Overall, we observed that there were positive effects of autumn fires on reproductive traits, while vegetative growth was positively related to fire severity and pre‐fire plant size.     

Kinetic complexity of chloroplastal deoxyribonucleic acid and mitochondrial deoxyribonucleic acid from higher plants

1. Chloroplasts and mitochondria were isolated by aqueous and non-aqueous cell-fractionation techniques. In a variety of higher plants the mitochondrial DNA bands in a caesium chloride gradient at 1.706g.cm.(-3), whereas chloroplastal DNA has a buoyant density of 1.697g.cm.(-3). 2. In total cellular DNA of moderate molecular weight, the chloroplastal DNA is found within the Gaussian distribution of the nuclear DNA and is not resolved as a satellite. 3. Both chloroplastal DNA and mitochondrial DNA from lettuce renature rapidly. 4. The kinetic complexity of mitochondrial DNA is > 10(8) daltons. 5. Chloroplastal DNA is made up from fast and slow renaturing sequences with kinetic complexities of 3x10(6) and 1.2x10(8) daltons respectively. 6. From the discrepancy between analytical and kinetic complexity it is concluded that chloroplastal DNA is extensively reiterated.     

Effects of soil properties and clonal growth on the apparent sex ratio of the flowering stems of the dioecious clonal shrub Aucuba japonica var. borealis growing in an evergreen coniferous secondary forest

In dioecious plants, the frequencies of flowering stems in each sex produced through clonal growth provide important information on the potential for reproductive success in the populations. However, apart from the light environment in their habitat, the factors affecting the flowering of each sex have not been well documented in shrub species that can maintain their populations in shady environments. In this research, we investigated seven soil variables and the flowering of stems of Aucuba japonica var. borealis in patches of this dioecious clonal shrub with different apparent stem sex ratios in an evergreen coniferous secondary forest with a shady forest floor. Of the 53 patches examined, 52 contained stems with flowers. Flowering stem ratios exhibited a positive relationship with available soil phosphate but a marginal negative relationship with exchangeable magnesium, whereas soil water content was associated with a female-biased flowering sex ratio. Stem density tended to be negatively related to flowering stem ratios in patches containing stems with female flowers but not males. While the results demonstrate that abundant amounts of certain nutrients and moisture in soils promote the production of flowers and/or a bias toward femaleness in patches, it is suggested that antagonistic effects of cations in the soil can inhibit the flowering of both sexes. In addition, the trade-off between sexual reproduction and clonal propagation in the females may amplify the variations in flowering in the population.     

Auxins of non-flowering plants. I. Occurrence of 3-indoleacetic acid and phenylacetic acid in vegetative and fertile fronds of the ostrich fern (Matteucia struthiopteris)

Gas chromatography-mass spectrometry evidence is presented for the presence of both phenylacetic acid (PAA) and 3-indoleacetic acid (IAA) in vegetative and fertile tissues of the sporophyte of the ostrich fern [ Matteucia struthiopteris (L.) Todaro]. 3-Indolepropionic acid, tryptamine and 3-indoleacetonitrile were not found in tissue extracts, although small amounts of 3-indolebutyric acid and tryptophol may have been present. PAA was present in amounts higher than those found in flowering plants, while LAA levels fall within the angiosperm range. The levels of both auxins were higher in the younger vegetative tissues than in mature vegetative or fertile pinnae. Recent evidence for the occurrence of angiosperm growth hormones in ferns is discussed.     

CHARACTERIZATION OF STARCH GRAINS IN THE NONARTICULATED LATICIFER OF EUPHORBIA PULCHERRIMA (POINSETTIA)

Starch grain morphology in laticifer amyloplasts of Euphorbia pulcherrima Willd. (poinsettia) was examined for evidence of starch metabolism in vegetative and flowering plants. Laticifer starch grains in vegetative plants were rod shaped with lengths ranging from 3 to 60 μm. Average grain size was significantly larger in stems than leaves, and in older than younger tissues. Starch grain length frequency was unimodal and approximated a normal probability distribution in stems, but was skewed positively toward smaller grains in leaves. Frequency distributions were shifted toward larger grains in older tissues. Under short-day photoperiod (flowering) conditions, round starch grains formed in latex of stems, and the average length of rod-shaped grains decreased in latex of stems and leaves. Round grains did not occur in laticifers of leaves or bracts. Round starch grains often occurred in aggregates of two or more subunits. Changes in size and shape of latex starch grains indicate that amyloplasts in fully differentiated laticifers metabolize starch. Identification of metabolically active amyloplasts in differentiated laticifers suggests that the function of these organelles may involve starch mobilization under certain physiological conditions.     

Effect of photoperiod during growth of Chenopodium rubrum mother plants on properties of offspring

Using in vitro culture, we determined the effect of photoperiod during growth of Chenopodium rubrum mother plants on vegetative and reproductive development of offspring. Photoperiod during flowering induction of mother plants (the first 6 d after the germination) has the key influence on seed germination and offspring growth, while offspring flowering and seed maturation is determined by photoperiod their mothers experienced during, and shortly after, flowering induction. The mechanism can be through changes in seed protein pattern which we found dependent on photoperiod experienced by mother plants.