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As a result of its domestication, breeding and subsequent commercialization, African violet (Saintpaulia ionantha H. Wendl.) has become the most famous and popular Saintpaulia species. There is interest in producing cultivars that have increased resistance to pests and low temperature, in the introduction of novel horticultural characteristics such as leaf shape, flower colour, size and form, and in improved productivity and enhanced flower duration in planta. In African violet, techniques such as the application of chemical mutagens (ethylmethanesulfonate, N-nitroso-N-methylurea), radiation (gamma (γ)-rays, X-rays, carbon ion beams) and colchicine have been successfully applied to induce mutants. Among these techniques, γ radiation and colchicine have been the most commonly applied mutagens. This review offers a short synthesis of the advances made in African violet breeding, including studies on mutation and somaclonal variation caused by physical and chemical factors, as well as transgenic strategies using Agrobacterium-mediated transformation and particle bombardment. In African violet, Agrobacterium-mediated transformation is affected by the Agrobacterium strain, selection marker, and cutting-induced wounding stress. Somaclonal variation, which arises in tissue cultures, can be problematic in maintaining true-to-type clonal material, but may be a useful tool for obtaining variation in flower colour. The only transgenic African violet plants generated to date with horticulturally useful traits are tolerant to boron (heavy metal) stress, or bear a glucanase-chitinase gene.

In this study, we revealed how the petals of Saintpaulia fuse into a corolla by using pinwheel phenotype cultivars. Striped patterns in petal, called pinwheel in Saintpaulia, are attractive phenotypes and thought to be the result of periclinal chimerism. For the selection of a genuine periclinal chimeric cultivar from three pinwheel cultivars, adventitious shoots were induced from leaf lamina. Shoot regeneration was observed from the epidermis in all cultivars by microscopic observation. All regenerated shoots from ‘Kaname’ flowered as monochromatic pink flowers, corresponding to an L1 phenotype of the cultivar. From the other two cultivars, many shoots flowered not only as an epidermal phenotype but also as a phenotype of the inner layer. In addition, shoot regeneration was induced from epidermis-peeled petioles from these three cultivars. All shoots from ‘Kaname’ flowered as monochromatic blue flowers, corresponding to an L2 phenotype. On the other hand, many shoots from ‘Kilauea’ flowered not only as monochromatic flowers, corresponding to an L2 phenotype, but also as bi-colored flowers. ‘Innocent Pink’ did not produce shoots from epidermal-peeled petioles. These results suggested that ‘Kaname’ is a genuine periclinal chimera, while the other two cultivars have other mechanisms for pinwheel expression. Genomic PCR using primers that amplifies almost the full length of flavonoid 3′,5′-hydroxylase (F3ʹ5ʹH) revealed the gene to be non-functional in pink flowers from L1 of ‘Kaname’. From monochromatic pink plants and pink portions of the corolla of ‘Kaname’, full-length F3ʹ5ʹH was not amplified. Similar results were obtained by quantitative PCR. Finally, we observed the fused portion of the petals and revealed that the petal fusion did not occur by postgenital fusion but by “connection”. The process, in Saintpaulia, comprises periclinal cell division in L1 during petal development, active cell division at the edge of the petal, adhesion to the next petals, and fusion. These steps create a striped flower color in Saintpaulia.

African violet (Saintpaulia ionantha H. Wendl.) (Gesneriaceae) is a popular ornamental pot plant that is easy to culture ex vitro and in vitro relative to other herbaceous ornamentals. This quality makes it an ideal system for in vitro regeneration experiments. This review summarizes the studies that have been conducted on the in vitro culture and micropropagation of this plant. Although shoot regeneration from internodes, floral buds, anthers and protoplasts has been achieved, leaf blades and petioles have been a popular source tissue for regeneration. An effective and reproducible protocol for the direct induction of shoots, without the formation of any intermediary callus, involves the use of a cytokinin like BA or kinetin, usually in combination with an auxin like NAA, both within a concentration range of 0.1 to 1 mg/L, and on a Murashige and Skoog basal medium. Shoots can form in both light and darkness, but most effectively in the light, and rooting can be induced from shoots, even in the absence of an auxin, although a low concentration (0.1–0.5 mg/L) of NAA or IAA is recommended. African violets acclimatize easily, even in a simple soil-based substrate, and can flower within 4 months of transfer to ex vitro conditions. These protocols, including somatic embryogenesis and cryopreservation, may also benefit the in vitro culture and conservation of wild species of Saintpaulia.

Background The African violets are endangered plant species restricted mainly to the Eastern Arc Mountains biodiversity hotspots in Kenya and Tanzania. These plants grow well in shaded environments with high humidity. Given their restricted geographical range and published evidence of dependance on insect vectors to facilitate sexual reproduction, understanding their pollination biology is vital for their survival. Methods We conducted an empirical study using flower visitor observations, pan trapping and bagging experiments to establish the role of flower visitors in the fruit set of a locally endemic and critically endangered species of African violet in Taita Hills, Kenya, Streptocarpus teitensis. Results The study found that fruit set is increased by 47.8% in S. teitensis when flowers are visited by insects. However, it is important to note the presence of putative autogamy suggesting S. teitensis could have a mixed breeding system involving self-pollination and cross-pollination since bagged flowers produced 26.9% fruit set. Conclusions Insects appear to be essential flower visitors necessary for increased fruit set in S. teitensis. However, there is evidence of a mixed breeding system involving putative self-pollination and cross-pollination suggesting that S. teitensis is somewhat shielded from the negative effects of pollinator losses. Consequently, S. teitensis appears to be protected to a degree from the risks such as reproduction failure associated with pollinator losses by the presence of a safety net in putative self-pollination.

The color of African violet flowers (Saintpaulia ionantha Wendl.) is derived from anthocyanin pigments. A mutation in the L1 layer of the SAM suppresses the anthocyanin biosynthesis pathway and eventually generates a pinwheel phenotype of periclinal chimera (cells of different genotypes). The aim of the present research was to understand the coloration pathway of petals and how color changes with phenotype. Flower development was investigated by light and scanning electron microscopy (SEM). Expression of nine genes involved in anthocyanin biosynthesis pathway in monochromatic and pinwheel phenotypes were evaluated by Real-Time PCR. Anthocyanin present in pinwheel petals was analyzed by HPLC. Microscopic studies revealed that the ventral petals were formed before the dorsal petals and that the petal primordia separated in the early stages of floral development. Saintpaulia flower is protandry and the tapetum layer is of the secretory type. The ovules are anatropous and are within the superior ovary with lateral placentation. Gene expression analysis showed that CHS and CHI genes were expressed at all stages of floral development, but hydroxylase genes increased during intermediate stages. Biosynthetic genes were highly expressed in the purple sections of the pinwheel petals, whereas the expression of F3H gene was significantly lower in the white section. The WDR transcription factor appears to have no association with the anthocyanin biosynthesis pathway genes in the white section. HPLC analysis showed that when F3H gene expression was reduced in the white part of the petals, the product of this gene (dihydrokaempferol component) did not accumulate. Color change is one of the most effective methods to create new cultivars. Details of floral pigment biosynthesis pathway and the production of new cultivars can respond to consumer demand and market preservation.

To optimize the production of anther-derived haploid plants of the genus Saintpaulia, the effect of plant growth regulator (PGR) concentration in the induction medium was investigated for six Saintpaulia species and eight cultivars of S. ionantha. The most effective PGR concentration for shoot formation was 1.0 mg l−1 for both N6-benzyladenine and α-naphthaleneacetic acid among the nine combinations of three concentrations (0.1, 1.0 and 10.0 mg l−1) of each PGR. Microspores at the uninucleate stage, which is the most suitable stage for anther culture, were observed in buds 2–3 mm (in Saintpaulia species) or 3–5 mm (in S. ionantha cultivars) in length. The frequency of shoot formation from anther-derived calli ranged from 0 to 63 % for Saintpaulia species and 0 to 100 % for S. ionantha cultivars. Five Saintpaulia species and seven S. ionantha cultivars formed shoots under the same PGR concentrations. These results demonstrated the versatility of the optimized conditions for anther cultures of diverse genotypes in Saintpaulia. Microscopic observation of the chromosomes of root-tip cells of anther-derived plants showed that the haploid efficiency was 40.0–85.7 % (average 66.6 %). Some haploid individuals showed phenotypic differences from the diploid parents in flower color and shape. Significant differences in stomatal guard cell lengths were observed between the diploid parent and some of the anther-derived haploids. The described protocol enabled haploids of Saintpaulia species to be obtained in a minimum of 286 days.

Saintpaulia ionantha is propagated by adventitious buds in horticulture, and periclinal chimeric cultivars are usually difficult to propagate. However, some periclinal chimeric cultivars can be propagated with adventitious buds, and the mechanism of which has been unknown. Striped flower cultivars “Kaname”, “Concord”, and “Monique” were used to investigate what causes flower color separation in adventitious shoot-derived plants by tissue culture. These cultivars were revealed to have mutated flavonoid 3', 5' hydroxylase (SiF3'5'H), WDR1 (SiWDR1), or flavonoid 3 hydroxylase (SiF3H), respectively, in their L1 layer. From our previous study using “Kaname”, all flowers from adventitious shoots were colored pink, which was the epidermal color of mother plants’ flowers. We used “Concrd” and “Monique” from which we obtained not only monochromatic-colored plants the same as the epidermal color of mother plants, but also plants with a monochromatic colored plants, same as the subepidermal color, and a striped flower color the same as mother plants. Histological observations revealed that epidermal cells divided actively at 14 d after culture and they were involved in the formation of adventitious shoots in the cultured leaf segments of “Kaname”. On the other hand, in “Concord” and “Monique”, the number of divided cells in the subepidermis was rather higher than that of epidermal cells, and subepidermal cells were sometimes involved in shoot formation. In addition, the plant and leaf size of L1-derived plants from “Concord” and “Monique” were non-vigorous and smaller than those derived from the subepidermal layer. In conclusion, periclinal chimeric cultivars of Saintpaulia can be divided into two types. One type has a high cell division activity in the L1 layer, from which only single flower-colored plants derived from L1 can be obtained as adventitious shoots. Another type has a low cell division activity in the L1 layer, from which striped flower-colored plants the same as mother plants derived from several layers including L1 can be obtained as adventitious shoots. In the periclinal chimeric cultivar capable of propagation with adventitious shoots, the possibility was shown that cells in the L2 layer could form shoots by involving cells of the L1 layer with a low division activity.

For rapid multiplication and genetic manipulation of African violets (Saintpaulia ionantha Wendl.) was aimed at developing a rapid and efficient regeneration and adaptation system from leaf explants. Using RM medium supplemented with different combinations of growth regulators, we developed a highly efficient and time-saving in vitro regeneration protocol. The developed system was also successfully applied for plant regeneration from petiole and internode explants of several Saintpaulia cultivars at a high efficiency. Regeneration occurred through both somatic embryogenesis and shoot organogenesis at a high frequency. Also, we developed a rapid root formation protocol followed by their efficient adaptation for in vitro regenerated plantlets. Plant Tissue Cult. & Biotech. 24(1): 37-45, 2014 (June) D. O. I. http://dx.doi.org/10.3329/ptcb.v24i1.19194

Resumen Las “violetas africanas” Saintpaulia ionantha H. Wendl. (Gesneriaceae) son plantas ornamentales muy valoradas en el mundo por su belleza y capacidad de dar flores durante todo el ano. Esto ha conllevado a que su demanda sea mayor, pues es idonea para decorar espacios interiores del hogar. Por ello, su cultivo con fines comerciales ha aumentado, siendo la propagacion in vitro y su posterior aclimatacion una buena alternativa de emprendimiento en floricultura. Sin embargo, ante escasa informacion referida a la aclimatacion ex vitro de S. ionantha , se propuso como objetivo estandarizar un protocolo de aclimatacion. Para ello, se seleccionaron plantulas in vitro del Laboratorio de Biotecnologia del Instituto de la Papa y Cultivos Andinos, las cuales fueron transportadas al invernadero para su siembra, empleandose diferentes sustratos, constituidos por: T1 = arena + musgo + humus; T2 = arena + musgo; T3 = arena + humus y T4 = arena. Se encontraron diferencias estadisticamente significativas, siendo el tratamiento T1 el que evidencio un buen porcentaje de plantas aclimatadas, el mayor porcentaje de plantas enraizadas, el mayor numero promedio de hojas, el mayor numero promedio de raices normales, y la mayor longitud y ancho promedio de hoja. Se concluye que el sustrato constituido por arena + musgo + humus es el mas optimo para la aclimatacion ex vitro de S. ionantha . Palabras clave: aclimatacion, plantulas, in vitro , Saintpaulia , “violeta africana”. Abstract “African violets” Saintpaulia ionantha H.Wendl. (Gesneriaceae) are ornamental plants very valued in the world for their beauty and ability to give flowers throughout the year. This has brought an increase in their demand, as they are suitable for decorating interior spaces at home. That is the reason because their cultivation for commercial purposes has increased, and the propagation in vitro and its subsequent acclimation is a good alternative of entrepreneurship in floriculture. However, the scarce information of ex vitro acclimation of S. ionantha leads us to propose a standard acclimation protocol. For this purpose, we selected in vitro seedlings from the Biotechnology Laboratory of the Potato and Andean Crops Institute. They were transported to greenhouse for planting using different substrates consisting of: T1 = sand + moss + humus; T2 = sand + moss; T3= sand + humus and T4 = sand. Statistically significant differences were found, with treatment T1 showing a good percentage of acclimated plants, the biggest percentage of rooted plants, the biggest average number of leaves, the biggest average number of normal roots and the biggest average leaf length and width. It was concluded that the substrate constituted by sand + moss + humus is the most optimal for ex vitro acclimation of S. ionantha . Keywords: acclimation, seedlings, in vitro, Saintpaulia ; “african violet”.

Within the family Gesneriaceae, the two related genera Saintpaulia and Streptocarpus contain species that are used as ornamental potted plants. Crosses within the genus Streptocarpus subgenus Streptocarpella and between Streptocarpus and Saintpaulia ionantha were carried out to produce new ornamental plants. Crossing barriers were localised, and methods to overcome these barriers were tested. The in vitro germination ability of pollen was determined; germination varied from 3 to 85% among genotypes. A high correlation coefficient of 0.99 was found between the assessment of pollen viability using staining with 2,5-diphenyl tetrazolium bromide (MTT) and in vitro germination. From crosses of nine Streptocarpus species from the subgenus Streptocarpella, 11 hybrids were established. Hybridity was confirmed in five of these crosses by morphological and RAPD (random amplified polymorphic DNA) marker analysis. An embryo rescue technique was used in an attempt to overcome existing post-zygotic barriers in intergeneric crosses between S. ionantha and Streptocarpus species. Despite swelling of the ovules, which is usually considered as an indicator for successful fertilisation, no germination of plants from embryos was observed with this method.

This study has been performed to investigate the efficiency of the chemical mutagen ethyl methanesulphonate (EMS) to induce mutations in Saintpaulia. In vitro leaf sections of Saintpaulia cv. Crystobal were exposed to various EMS treatments at 0%, 0.2%, 0.4%, and 0.6% for 30, 60, 120, and 240 min after which adventitious shoots were recovered from the treated explants. Shoots producing at least six leaves were induced to root and the resulting plantlets were transplanted to soil. A total of 1838 plantlets was grown to flowering stage and 10 mutants were identified. Four of the mutants were variegated leaf chimeras and the remaining six presented variations at the level of flower color and/or fringe. Results in the present study showed the efficiency of EMS to induce in vitro mutation of Saintpaulia and the method can be used in the future to assist breeding in this popular ornamental plant. Saintpaulia (family Gesneriaceae), commonly known as African Violet, is a popular houseplant as a result of its compact size, tolerance of shaded conditions, ease of vegetative propagation, and potential to flower year round. To date 20,000 varieties have been produced globally by conventional hybridization techniques and spontaneous mutation, and annually, several hundred new cultivars are released (Ghisleni and Martinetti, 1995). The breeding of Sainpaulia is nevertheless hampered by the low number of wild species available for crosses and the low spontaneous mutation frequencies. For commercial floriculture, development of new and improved varieties is important because it will keep up the interest of the consumers. Today, biotechnological approaches (e.g., mutation breeding, genetic transformation) have proved to be a powerful tool to complement the traditional breeding works in many ornamental species. Mutation breeding has become increasingly popular in recent times as an effective tool for crop improvement, and more than 2250 mutant cultivars have been released worldwide (Ahloowalia et al., 2004). Artificial mutation induction can be carried out using physical and chemical mutagens and mutation induction with radiation was the most frequently used method to develop direct mutant varieties (Ahloowalia et al., 2004). Several reports on the induced mutation of Saintpaulia using physical mutagens such as ion beam, x-ray, and gamma ray were published in the past (Leenhoots et al., 1982; Wongpiyasatid et al., 2007; Zhou et al., 2006). In these works, although variants were observed in the regenerated shoot population, the procedure required expensive units to operate, which is out of scope for most research and commercial laboratories. Chemical mutagens could be successfully applied to induce mutations where no irradiation facility is available. In some cases, the efficiency of chemical mutagens has proved to be greater than those of physical mutagens (Jacobs, 2005; Rego and Faria, 2001). Among the chemical mutagens, EMS is considered very effective and its effectiveness has largely been demonstrated in cereal crops such as rice (Bhan and Kaul, 2003), wheat (Bozzini and Mugnozza, 2003), and barley (Nicoloff, 2003) as well as in Arabidopsis thaliana (Jacobs, 2005). Recently, this mutagen has also been used to treat seeds and in vitro propagules of many species (Basu et al., 2008; Latado et al., 2004; Luan et al., 2007). To our knowledge, there is no report so far on the EMS use in Saintpaulia; it is therefore our objective to study the possibility of using this mutagen to induce mutations in in vitro-grown Saintpaulia. Materials and Methods Saintpaulia cv. Crystobal is a standardsized cultivar with a rosette growth habit. Its flowers are double ( 3 to 4 cm in diameter), magenta in color, and present a white fringe around the lobes. The leaves are plain green. This cultivar is fast-growing, moderately tolerant to heat so it is popularly sold in warm climate countries such as Taiwan. For the initiation of aseptic culture, young expanding leaves were dissected and washed under running tap water for 5 min to remove superficial dirt. They were then washed with a detergent solution (consisting of one drop of household detergent in 100 mL of water) for 10 min. After several rinses with tap water, the leaves were transferred inside a laminar flow cabinet. Surface sterilization of the leaves was carried out with 70% ethanol for 1 min followed by 0.5% sodium hypochlorite disinfection for 10 min; a few drops of Tween-20 were added as a surfactant. Both steps were conducted on an orbital shaker set at 150 rpm. The leaves were finally rinsed three to four times with sterile distilled water to remove traces of sodium hypochlorite. Sterilized leaves were cut into 0.5 cm · 0.5cm sections and each section was placed, with its abaxial side touching the medium, in a test tube containing 15 mL of the African Violet Multiplication (AVM) medium. The AVM medium consisted of full-strength Murashige and Skoog (MS) (Murashige and Skoog, 1962) salts and vitamins, 30 g L sucrose, 0.5 mg L benzyl adenine, 0.1 mg L a-naphtaleneacetic acid, and 7 g L agar. The pH of the medium was adjusted to 5.7 before sterilization in an autoclave at 121 C, 15 psi for 15 min. The explants were maintained on AVM medium for a total duration of 8 weeks. Induced adventitious shoots were transferred into 175-mL glass jars containing 60 mL of MS medium devoid of growth regulators for further shoot development. Two months later, leaves were excised from the grown up shoots and cut into 0.5 cm · 0.5-cm sections again and thus initiating a new multiplication cycle. The shoots obtained after several multiplication cycles were then used for the mutation experiment. EMS is a potential carcinogen so its preparation and handling were conducted inside a chemical fume hood. A 1% stock solution of EMS was first prepared using distilled water. This stock solution was then used to prepare 0%, 0.2%, 0.4%, and 0.6% EMS solutions using 0.1 M phosphate buffer (pH 7.2). The various EMS solutions were filter-sterilized (through a 0.2-mm membrane) before use. Leaf sections measuring 0.4 cm · 0.4 cm were immersed in 0%, 0.2%, 0.4%, and 0.6% EMS solutions for 0, 30, 60, 120, and 240 min with constant swirling throughout the treatment. After the treatments, the explants were rinsed three times with sterile distilled water and blotted dried on a sterile filter paper. They were plated on AVM medium for shoot regeneration. The frequency of explant survival was recorded at Week 4 and the frequency of explants producing shoots was observed at both Weeks 4 and 8 after EMS application. Explants were considered alive if they Received for publication 14 Apr. 2011. Accepted for publication 30 May 2011. To whom reprint requests should be addressed; e-mail jyfang@mail.npust.edu.tw. HORTSCIENCE VOL. 46(7) JULY 2011 981 exhibited any kind of growth. The EMS experiment was arranged in a completely randomized design. There were 20 leaf explants per treatment and the experiment was conducted twice. Data were subjected to analysis of variance (Version 9.0; SAS Institute Inc., Cary, NC) and treatment means were ranked according to Duncan’s multiple range test and difference tested at 5% probability. By the end of the eighth week, regenerated shoots were transferred onto plant growth regulator-free MS medium and the subculture was conducted every 30 d. Two months later, the in vitro plantlets were acclimatized and grown in a pre-sterilized substrate composed of peat, vermiculite, and perlite at a ratio of 1:1:1. Selection of mutants was conducted at the flowering stage of the plants. All the cultures (i.e., in vitro and acclimatized plantlets) were maintained at 25 ± 2 C with a 16-h photoperiod provided by 40 mmol m s L cool white fluorescent lamps.

We have developed LED (light emitting diode) induced fluorescence transient imaging instrumentation to image the plant health/stress status by calculation of two images: Fv/Fm (variable fluorescence over saturation level of fluorescence) and the time response, tTR, of the fluorescence time curve. Within a short time interval (˜580 ms) multiple images (typically 20) are captured using the LEDs in the pulsed mode. For each pixel of the fluorescence image Fv/Fm and tTR are calculated and presented as images that correlate with the quantum yield of PSII photochemistry and the time response of this process, respectively. The advantage of the technology lies in the imaging of photosynthetic parameters within a short time interval, remotely and under light conditions. This was accomplished by the development of a high intensity pulsed LED light source (total 5 kW electrical power) and using the LEDs in the pulsed mode with a pulse width of 15 ms and time between sequential pulses of 14 ms. Using this instrumentation we investigated the effect of herbicide treatment, Sencor, on black nightshade (Solanum nigrum L.) plants. Effects of the herbicide on the first fluorescence images could be detected. At the saturation level of the fluorescence this effect disappeared. The effect of the herbicide was visualized on the Fv/Fm image and the time response tTR image. Healthy and herbicide treated parts of the plant yielded average values of Fv/Fm=0.81±0.03 and 0.06±0.02, respectively. Furthermore, the effect of drought stress was investigated on saintpaulia (Saintpaulia ionantha) plants. Under dark conditions no differences in the image of Fv/Fm and tTR could be detected between the control and the plant with drought stress. Under actinic light of 90 µmol m-2 s-1 differences were observed in images of (Fm’-F’)/Fm’ and tTR’. We conclude that for the first time images of a time response of the photosynthesis of leaves are presented. Furthermore, the proposed instrumentation can be used for high throughput screening, as a sensor in sorting machines and has potential greenhouse applications.

The Gesneriaceae (Lamiales) is a family of flowering plants comprising >3000 species of mainly tropical origin, the most familiar of which is the cultivated African violet ( Saintpaulia spp.). Species of Gesneriaceae are poorly represented in the lists of taxa sampled for genome size estimation; measurements are available for three species of Ramonda and one each of Haberlea , Saintpaulia, and Streptocarpus , all species of Old World origin. We report here nuclear genome size estimates for 10 species of Sinningia , a neotropical genus largely restricted to Brazil. Flow cytometry of leaf cell nuclei showed that holoploid genome size in Sinningia is very small (approximately two times the size of the Arabidopsis genome), and is small compared to the other six species of Gesneriaceae with genome size estimates. We also documented intraspecific genome size variation of 21%–26% within a group of wild Sinningia speciosa (Lodd.) Hiern collections. In addition, we analyzed 1210 genome survey sequences from S. speciosa to characterize basic features of the nuclear genome such as guanine–cytosine content, types of repetitive elements, numbers of protein-coding sequences, and sequences unique to S. speciosa. We included several other angiosperm species as genome size standards, one of which was the snapdragon ( Antirrhinum majus L.; Veronicaceae, Lamiales). Multiple measurements on three accessions indicated that the genome size of A. majus is ∼633 × 106 base pairs, which is approximately 40% of the previously published estimate.

Mating among closely-related individuals in small and isolated plant populations may result in reduced vigour of the inbred offspring, i.e. inbreeding depression, especially in naturally outbreeding plants. Occurrence of inbreeding and inbreeding depression was studied in Saintpaulia ionantha ssp. grotei, a threatened endemic plant species with a narrow ecological amplitude from the East Usambara Mountains. The level of inbreeding (measured as the fixation index, F) was investigated in twelve populations by analyzing variation at one microsatellite marker locus. The effect of one generation of selfing and outcrossing on the progeny fitness was studied by controlled crosses in two small patches that differ in the level isolation. The fixation index (F) across the populations was on the average 0.21 and varied among the populations from substantial inbreeding (F = 0.58) to surplus heterozygosity (F = −0.29). High inbreeding depression (δ) was observed at early and late stages of the life-cycle. The isolated patch exhibited lower inbreeding depression than did the non-isolated patch. The results of this study suggest that inbreeding and subsequent inbreeding depression are potential threats to the survival of Saintpaulia populations. Resume L’accouplement d’individus etroitement lies, dans des petites populations vegetales isolees, peut aboutir a une vigueur moindre de la progeniture de meme souche, c’est-a-dire une depression due a l’endogamie, specialement chez des plantes qui sont naturellement exogames. L’occurrence de l’endogamie et de la depression qui y est liee a eteetudiee chez le Saintpaulia ionantha spp. grotei, une plante endemique menacee qui n’a qu’une faible amplitude ecologique dans l’est des Usambara Mountains. On a recherche le taux d’endogamie (mesure par l’indice de fixation F) dans 12 populations en analysant la variation d’un locus microsatellite marqueur. L’effet d’une generation d’auto- et d’allofecondation sur l’aptitude (fitness) de la progeniture a eteetudie par des croisements controles dans deux petites parcelles dont le degre d’isolement differait. L’indice de fixation F dans les populations etait en moyenne de 0,21 et il variait d’une autofecondation substantielle (F = 0,58) a une heterozygosite en surplus (F = −0,29). Une forte depression due a l’endogamie (δ) a ete observee aux stades precoce et tardif du cycle vital. La parcelle isolee a presente une depression liee a l’endogamie moins forte que celle de la parcelle non isolee. Les resultats de cette etude suggerent que l’auto-fecondation et la depression qui en resulte sont des menaces potentielles pour la survie des populations de Saintpaulia.

Saintpaulia (H. Wendl.) is a forest-dependent, endangered plant genus endemic to Tanzania and Kenya. The taxonomy of Saintpaulia from the Usambara Mountains and adjacent lowlands in north-eastern Tanzania is problematic because of the morphological similarity of the species and the presence of considerable intraspecific variation. Conventional molecular phylogenetic methods have failed to reveal the genetic structure of this Saintpaulia complex. In this study, we assessed the genetic composition of 12 Saintpaulia populations, representing four different morphotypes, from the East Usambara Mountains using inter-simple sequence repeat (ISSR) markers. Relatively high genetic diversities were observed within populations (mean h = 0.320), indicating their adaptive potential. Little genetic differentiation amongst populations (mean Fst = 0.063) and the genetic divergence of the rosulate and trailing morphotypes support the hypothesis of ongoing divergent evolution within the East Usambara metapopulation(s) of Saintpaulia. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 347–355.

Floral development and inflorescence structure within Streptocarpus and Saintpaulia were investigated using Scanning Electron Microscopy (SEM). We discuss the structure and development of the pair-flowered cyme and the floral ontogeny found in the Gesneriaceae in a phylogenetic context with particular reference to an East African clade of Streptocarpus and Saintpaulia. Current phylogenetic hypotheses divide the caulescent East African Streptocarpus species into two distinct clades, in relation to which the position of Saintpaulia is not yet clear. Variation in the branching of the inflorescence showed phylogenetic significance and included dichasial, monochasial and unbranched patterns. In four of the East African Streptocarpus species sampled a single lateral bracteole was present on the first to third axes, after which the inflorescence was ebracteolate. Our results indicate that there may be some link between bracteole suppression and an alteration in the order of sepal initiation. The loss or suppression of lateral bracteoles also appears to result in the precocious development of the lateral cyme meristem.

Climatic seasonality, local habitat quality, and edge effects created by forest fragmentation due to human activity may affect the performance of endangered rain forest understory herbs. Viability and seasonal dynamics of the populations of the endangered Saintpaulia confusa, S. difficilis, and S. grotei were studied in a protected seasonal submontane forest in NE Tanzania by examining plant life-history traits, population stage structure, and the effects of habitat quality on plant performance. The population stage structures were of the dynamic type. There was a lower frequency of seedlings (57.9%) and higher frequency of juvenile (13.3%) and adult plants (28.8%) in S. confusa than in S. difficilis (74%, 10.7% and 15.3%, respectively). Seedling recruitment occurred from May to August with an average of 54, 103 and 38 emerged seedlings per 1 m2 study plot (S. confusa, S. difficilis, and S. grotei, respectively). Presence of the seed bank was also an indication of the regeneration potential of the populations. Mortality was high during the dry and hot season from December to March. Survival was lowest in juvenile plants, higher in sterile adult plants and the highest in fertile adult plants. Because survival was the lowest on dry substrates under open canopy, our data suggest that forest fragmentation, by reducing shade and humidity, will increase mortality in Saintpaulia. Furthermore, since the mortality was highest in seedlings and juveniles, forest fragmentation is likely to impede the regeneration of the Saintpaulia populations.

The plant genus Saintpaulia (African violet) is endemic to a small area in northeastern Tanzania and has undergone a recent radiation producing species which are difficult to distinguish morphologically. Previous molecular work identified a group of eleven species of the ionantha complex that are indistinguishable using sequence analysis of the internal transcribed spacer (ITS) of the ribosomal DNA gene. Exon 2 of the chalcone synthase (CHS) gene was PCR amplified producing 21 sequences from Sa. ionantha and 11 sequences from four other Saintpaulia species. The genus Saintpaulia contains two CHS genes (SaCHSA and SaCHSD). SaCHSD was used to construct a gene tree of six species. The sequence analysis clearly distinguishes four of the five closely related species of the ionantha complex.

Knowledge of the reproductive biology of endangered plants is essential for their effective conservation. It also provides important information for understanding the evolutionary processes that affect speciation, thus helping the definition of proper units for conservation in endangered plants with problematic taxonomy. We studied the reproductive potential and possibility for hybridization in the endangered genus Saintpaulia (Gesneriaceae) by examining flowering phenology, flower and seed production and pollination of three sympatric cross-compatible Saintpaulia species in the East Usambara Mts., Tanzania. The synchrony observed in flowering in S. confusa and S. difficilis may enable hybridization between these two species, whereas partial phenological separation may contribute to the integrity of S. grotei. Although the level of flower abortion is high in S. confusa, each pollinated flower yields about 1000 seeds. Saintpaulia confusa produces fruits following both self- and cross-pollination but spontaneous self-pollination seems not to occur. Thus, seed production depends on sufficient pollinator service. Floral heteromorphy (i.e. enantiostyly) and bee pollination are likely to further enhance cross-pollination, suggesting that the genus predominantly outcrosses. Thus, Saintpaulia populations are likely to suffer from negative effects of inbreeding if they become small and isolated. Resume La connaissance de la biologie de la reproduction des plantes en danger est essentielle pour l'efficacite de leur conservation. Elle fournit aussi des informations importantes pour la comprehension des processus evolutifs qui touchent la speciation et donc pour la definition d'unites adequates pour la conservation de plantes en danger dont la taxonomie pose des problemes. Nous avons etudie le potentiel reproductif et la possibilite d'hybridation du genre menaceSaintpaulia (Gesneriaceae) en examinant la phenologie de la floraison, la production de fleurs et de semences, et la pollinisation de trois especes de Sainpaulia sympatriques de l'est des Usambara Mountains, en Tanzanie, qui peuvent se croiser. La synchronie de la floraison observee avec S. confusa et S. difficilis permet peut-etre l'hybridation entre ces deux especes, tandis qu'une separation phenologique partielle pourrait contribuer a conserver l'integrite de S. grotei. Meme si le niveau d'avortement est eleve pour les fleurs de S. confusa, chaque fleur fecondee produit environ 1000 semences. S. confusa produit des fruits apres la pollinisation par sa propre espece ou par croisement avec une autre espece, mais il semble qu'il n'y ait pas d'auto-pollinisation spontanee. Donc, la production de semences depend de l'abondance des pollinisateurs. L'heteromorphie florale (i.e. enantiomorphisme) et la pollinisation par les abeilles sont susceptibles de stimuler la pollinisation croisee, ce qui suggere que ce genre se reproduit surtout de cette facon. Il est donc probable que les populations de Saintpaulia risquent de souffrir des effets negatifs de l’inbreeding si elles deviennent trop petites et isolees.

The effects of 960 MeV carbon ion beam and 8 MeV X-ray irradiation on adventitious shoots from in vitro leaf explants of two different Saintpaulia ionahta (Mauve and Indikon) cultivars were studied with regard to tissue increase, shoots differentiation and morphology changes in the shoots. The experimental results showed that the survival fraction of shoot formation for the Mauve and Indikon irradiated with the carbon ion beam at 20 Gy were 0.715 and 0.600, respectively, while those for both the cultivars exposed to the X-ray irradiation at the same dose were 1.000. Relative biological effectiveness (RBE) of Mauve with respect to X-ray was about two. Secondly, the percentage of regenerating explants with malformed shoots in all Mauve regenerating explants irradiated with carbon ion beam at 20 Gy accounted for 49.6%, while that irradiated with the same dose of X-ray irradiation was only 4.7%; as for Saintpaulia ionahta Indikon irradiated with 20 Gy carbon ion beam, the percentage was 43.3%, which was higher than that of X-ray irradiation. Last, many chlorophyll deficient and other varieties of mutants were obtained in this study. Based on the results above, it can be concluded that the effect of mutation induction by carbon ion beam irradiation on the leaf explants of Saintpaulia ionahta is better than that by X-ray irradiation; and the optimal mutagenic dose varies from 20 Gy to 25 Gy for carbon ion beam irradiation.

To determine the effects of carbon ion beams with five different linear energy transfer (LET) values on adventitious shoots from in vitro leaf explants of Saintpaulia ionahta Mauve cultivar with regard to tissue increase, shoots differentiation and morphology changes in the shoots.In vitro leaf explant samples were irradiated with carbon ion beams with LET values in the range of 31 approximately 151 keV/microm or 8 MeV of X-rays (LET = 0.2 keV/microm) at different doses. Fresh weight increase, surviving fraction and percentage of the explants with regenerated malformed shoots in all the irradiated leaf explants were statistically analysed.The fresh weight increase (FWI) and surviving fraction (SF) decreased dramatically with increasing LET at the same doses. In addition, malformed shoots, including curliness, carnification, nicks and chlorophyll deficiency, occurred in both carbon ion beam and X-ray irradiations. The induction frequency with the former, however, was far more than that with the X-rays.This work demonstrated the LET dependence of the relative biological effectiveness (RBE) of tissue culture of Saintpaulia ionahta according to 50% FWI and 50% SF. After irradiating leaf explants with 5 Gy of a 221 MeV carbon ion beam having a LET value of 96 keV/microm throughout the sample, a chlorophyll-deficient (CD) mutant, which could transmit the character of chlorophyll deficiency to its progeny through three continuous tissue culture cycles, and plantlets with other malformations were obtained.

Hypersensitivity is induced in many species of Acanthaceae and Gesneriaceae by local mechanical wounding. Once a plant of these species sustains a wounded leaf, it exhibits a temporary hypersensitive state and severe injury easily occurrs even in unwounded leaves. Locally wounded African violet (Saintpaulia sp.) plants sometimes show severe injury even at a noninjurious temperature for this species. This study was aimed to clarify changes in the temperature sensitivity of hypersensitivity-induced African violet plants by local wounding. The basal leaves of African violet ‘Ritali’ plants were cut as a local wounding treatment. The locally wounded plants were transferred to growth chambers at various temperatures and we evaluated the degree of leaf injury using an analysis software. In locally wounded plants, temperature sensitivity increased and leaf injury was observed even at 11°C, which is a noninjurious temperature for unwounded African violet. Such a wound-induced sensitivity to low temperature treatment (7°C for 1 h) quantitatively increased with local wounding severity. For the investigation of time-course changes in the hypersensitive state (wounding memory) of locally wounded plants, the plants were transferred to low temperature conditions at various intervals after the wounding treatment. The wounding memory was short-lived, that is, it was generally observed immediately after local wounding and then almost disappeared 30 min after. In conclusion, the low temperature sensitivity of African violet plants was enhanced by prewounding treatment.

The relationship between the rate of temperature drop, observed by infrared video thermography, and leaf browning injury was investigated in Saintpaulia. The severity of leaf injury increased largely during the immersion of leaf (20°C) in water (5°C) for 10s, whereas no further increase in the severity of injury was observed thereafter. During 3s of leaf immersion at various temperatures of water, leaf injury was induced only when the rate of temperature drop was more than 3°C/s. In the case of decreasing leaf temperature from various initial temperatures (40°C, 35°C, 30°C), leaf injury was observed at smaller temperature difference between leaf and water when the initial leaf temperature was high. The rate of temperature drop was high when the leaf temperature at 33°C as dropped to 20°C (3.5°C/s) rather than from 23°C to 10°C (3.2°C/s), resulting in 53% and 32% injury on the leaf, respectively. The temperature drop of coated leaves following immersion in 7°C water showed a lower rate of temperature drop than uncoated leaves, resulting in 1/30 times of the injury in uncoated leaves. In addition, the severity of the injury decreased as the size of a water droplet decreased due to the slow drop in leaf temperature. The results suggest that a gradual drop in leaf temperature inhibits leaf injury even though the temperature difference between water and leaf is large.

FT-IR characterization of pollen biochemistry was analyzed to detect possible connection with the viability (by staining with potassium iodide, 25%) and the germination capacity (on solid nutrient medium), in 15Saintpauliagenotypes. Vibrational spectroscopy indicates that the pollen ofS. ionanthagenotype “Red Velvet” is rich in proteins, lipids, triglycerides, and esters and has a viability of 88.4% and a low germination capacity (27.16%). ForS. ionantha“Jolly Red” and “Lucky Ladybug” genotypes, pollen showed high viability (88.81–91.49%) and low germination capacity (23.02–9.17%), even though the pollen is rich in carbohydrates.S. ionantha“Aloha Orchid” genotype has the highest percentage of viability (94.32%) and germination capacity (45.73%) and a rich content of carbohydrates and polygalacturonic acids. InS. rupicolaandS. ionanthagenotypes, the rich content of polygalacturonic acids, lipids, and carbohydrates favourably influenced the germination capacity. Spectroscopic result indicates, through different absorbance band intensity, a possible link between biochemical composition, viability, and germination capacity ofSaintpauliapollen. To determine exactly the relation between biochemistry and biological processes, it is necessary to initiate quantitative researches.

Saintpaulia (African violet) leaves are known to be damaged by a rapid temperature decrease when cold water is applied to the leaf surface; the injury is ascribed to the chloroplast damage caused by the cytosolic pH decrease following the degradation of the vacuolar membrane in the palisade cells. In this report, we present evidence for the involvement of Ca(2+) in facilitating the collapse of the vacuolar membrane and in turn in the temperature sensitivity of Saintpaulia leaves. In the presence of a Ca(2+) chelator (EGTA) or certain Ca(2+) channel inhibitors (Gd(3+) or La(3+)) but not others (verapamil or nifedipine), the pH of the vacuole, monitored through BCECF (2',7'-bis(carboxyethyl)-4 or 5-carboxyfluorescein) fluorescence, did not increase in response to a rapid temperature drop. These pharmacological observations are consistent with the involvement of mechanosensitive Ca(2+) channels in the collapse of the vacuolar membrane. The high level of expression of an MCA- (Arabidopsis mechanosensitive Ca(2+) channel) like gene, a likely candidate for a mechanosensitive Ca(2+) channel(s) in plant cells, was confirmed in the palisade tissue in Saintpaulia leaves by using a newly developed method of gene expression analysis for the specialized small tissues.

The relationship between the susceptibility to rapid temperature drop induced leaf injury, i.e. “leaf spot”, and the antioxidant capacities of several Saintpaulia (African violet) cultivars was examined. Cultivars ‘Ritali’ and ‘Tamiko’, that are more susceptible to leaf spot caused by a rapid drop in leaf temperature from 30 to 15°C than are cultivars ‘Maui’ and ‘New Jersey’. The susceptible cultivars were also more susceptible to oxidative stress caused by H2O2 and active chlorine than the tolerant cultivars. Reduction of available chlorine, considered to be accelerated by antioxidants of leaf tissue, was rapid in ‘Maui’ and ‘New Jersey’. Activity of the antioxidant enzymes superoxide dismutase and catalase were higher in the leaves of ‘Maui’ and ‘New Jersey’ than in the susceptible cultivars. These findings show a correlation between leaf spot injury and antioxidant capacity in Saintpaulia leaves.

Spread of Phytophthora root and crown rot in three pot plant species was studied on ebb-and-flow benches where the nutrient solution was recirculated. The plant species and their respective pathogens were: Saintpaulia ionantha – P. nicotianae, Gerbera jamesonii – P. cryptogea, and Spathiphyllum wallissii – Phytophthora spp. Ebb-and-flow benches were infested with the pathogen using different methods: 18–25% of the plants on a bench were inoculated or potted in soil infested with the pathogen or the nutrient solution was infested by either zoospores or mycelium fragments. More than 80% of the inoculated Saintpaulia plants and 22% of plants potted in infested soil developed disease but no spread of the disease was observed. Infestation of the nutrient solution did not result in any diseased Saintpaulia plant. More than 70% of the Gerbera plants developed disease as a result of spread of the pathogen irrespective of the infestation method used. No significant spread of the disease was observed with inoculated Spathiphyllum plants nor from plants potted in infested soil. A few Spathiphyllum plants developed disease symptoms after infestation of the nutrient solution with zoospores. In one experiment, nearly all Spathiphyllum plants were diseased after infestation of the nutrient solution with mycelium fragments. The presence of an irrigation mat significantly reduced the spread of the Phytophthora disease in Gerbera and Spathiphyllum. The possibility of an irrigation mat acting as a filter for zoospores is discussed.

Erwinia chrysanthemi spp. are Gram-negative bacterial phytopathogens causing soft rots in a number of plants. The structure of the extracellular polysaccharide (EPS) produced by the E. chrysanthemi strain A350, which is a lac Z − mutant of the wild type strain 3937, pathogenic to Saintpaulia, has been determined using a combination of chemical and physical techniques including methylation analysis, low-pressure gel-filtration and anion-exchange chromatography, high-pH anion-exchange chromatography, partial acid hydrolysis, mass spectrometry and 1- and 2D NMR spectroscopy. In contrast to the structures of the EPS reported for other strains of E. chrysanthemi , the EPS from strain A350 contains d -GalA, together with l -Rha p and d -Gal p in a 1:4:1 ratio. Evidence is presented for the following hexasaccharide repeat unit: Download full-size image All the Erwinia chrysanthemi spp. studied to date have been analyzed by ribotyping and collated into families, which are consistent with the related structures of their EPS.

Summary A synopsis of the poorly known genus Linnaeopsis , endemic to the Uluguru Mts. in Tanzania, is provided. Three species are recognized: L. subscandens B. L. B urtt , L. heckmanniana E ngl . and L. alba (E. A. B ruce ) B. L. B urtt . L. heckmanniana is subdivided into two subspecies, ssp. heckmanniana and ssp. gracilis (E. A. B ruce ) W eigend , stat. nov., and also in L. alba two subspecies are distinguished, ssp. alba and ssp. edwardsii W eigend , subsp. nov. The latter is marked by rugose leaves with 5-to 6-celled trichomes on the adaxial side (vs. 3- to 4-celled hairs in ssp. alba ) and by different hair cover of the ovary and stem. The affinities of Linnaeopsis are discussed and an origin within or near Streptocarpus subg. Streptocarpus suggested. A close relationship with Saintpaulia appears rather unlikely.

Summary. Two new endemic species of Saintpaulia, S. ulugurensis Haston and S. watkinsii Haston (Gesneriaceae) are described from the Uluguru Mountains. Their discovery emphasises the need for additional floristic work to be carried out in this area and supports the calls for strong conservation measures for the fragile forest habitats of Tanzania.

Floral diversity in Streptocarpus and Saintpaulia can be classified into six distinct types on the basis of quantitative variation. Species are differentiated by overall flower size and by corolla lobe size in relation to corolla tube opening size, characteristics implicated in pollination ecology. Saintpaulia has a very short corolla tube and yellow protruding anthers, strikingly different from Streptocarpus , and probably associated with buzz pollination. Some species of Streptocarpus and all species of Saintpaulia are enantiostylous, a feature often linked to buzz pollination. Mapping of these floral characters onto a molecular phylogeny based on ITS sequence data showed that inStreptocarpus flower size evolved from small to large, with reversals in four species. The putatively bee pollinated ‘open-tubed’ type had two independent origins, and the putatively lepidopteran-pollinated ‘keyhole’ type had four separate origins. Enantiostyly had one or two origins. The degree of zygomorphy varies withinStreptocarpus/Saintpaulia. The most extreme difference is between Saintpaulia ionantha and aSaintpaulia peloric cultivar. The developmental basis of floral variation was compared using SEM in three very different types: Streptocarpus primulifolius, Saintpaulia ionantha and a Saintpaulia peloric cultivar. Differences in corolla tube length and zygomorphy are established very early in flower development. Small, early changes in flower development establish major changes in mature floral morphology.

vegetative structures among some species, and are among the few genera in the Gesneriaceac which include species with chromosome counts or 1/ = 15. The similarity of these features has indicated that the two genera are likely to be closely related. This study examines the sequences of the chloroplast gene ndhF among several representative species of SaiJJlpulIlia and representatives of Slreptocarpu.I' subgenera Strcplocarpella and StreptocarplI.l'. The results of this analysis are congruent with those of a previous analysis based on the nuclear ribosomal region, ITS. Sailltpalliia was found to be nested within Streptocarpll.l' subgenus Streprocarpella. The results raise the possibility of the taxonomic revision or these genera, and this is discussed. Comparisons between the data sets are made regarding utility of the two regions, sample size and outgroup.

The change in chlorophyll fluorescence was investigated using fluorescence microscopy at the initial stage of leaf spot occurrence in Saintpaulia ionantha H. Wendl. (African violet). When Saintpaulia leaf was exposed to a rapid temperature drop, fluorescence intensity declined very quickly within a very short time (20 s) and did not recover after rewarming. This abrupt reduction of chlorophyll fluorescence was caused even by 20°C water for just 2 s, when leaf temperature prior to treatment was 35°C. This change of chlorophyll fluorescence was observed only in the palisade cells in a leaf. In addition, ultrastructural study of the chloroplast of the palisade cells showed an abrupt disruption in the photosynthetic apparatus. These results indicate that the initial stage of leaf spot occurrence is developed very quickly within a very short time and that it might be caused by a different mechanism to conventional chilling injury.

introduction This paper is a preliminary assessment of the conservation status of Saintpaulia H. Wendl. in both the wild and in cultivation. The genus Saintpaulia has been promoted as a botanical ‘panda’ symbolizing the decline of the tropical moist forests, particularly the Eastern Arc mountains of East Africa. In spite of this and it’s familiarity through usage as a house plant there has been no recent review of the conservation needs of the genus. This paper represents an initial attempt to review the status of the genus and makes general recommendations on future conservation activities. The authors have collated and reviewed all the available current information on the genus Saintpaulia from literature, botanic garden databases, and the authors’ own field experience. Using the above information they have assigned an IUCN Category of Threat (IUCN, 1994) to each Saintpaulia species. This initial study highlights the current threats to saintpaulias in the wild, addresses some of the taxonomic problems that are in need of further research and makes recommendations for their conservation. The authors hope that the article will instigate further research, and promote collaboration between conservation organizations, governments and the horticultural industry.

Saintpaulia (Gesneriaceae) is confined in the wild to small patches of forest in East Africa (Tanzania and Kenya), with most of the species occurring in submontane or montane forest. However, a few species are known from lowland forests and this paper outlines the distribution and ecology of some of the species recorded from lowland sites. Additional sites for S. confusa B.L. Burtt, S. diplotricha B.L. Burtt, S. grotei Engl., S. ionantha H. Wendl, S. tongwensis B.L. Burtt and two, possibly new, species, have been located during recent field studies. One of the critically endangered species, S. tongwensis has featured previously in Curtis's Botanical Magazine (N.S. t. 11) and its illustration and description are repeated here.

The molecular phylogeny of African violets (Saintpaulia H. Wendl.), based on ribosomal DNA internal transcribed spacer (ITS) sequences, follows the disjunct biogeography of the genus. Sequence analysis by parsimony of 19 accessions, representing 17 currently recognized Saintpaulia species, resulted in four trees of 182 steps. The first major division is between S. goetzeana, from the Uluguru Mts, Tanzania, and the rest of the genus. The basal position of S. goetzeana, and its putative primitive characters, may indicate an Uluguru origin for Saintpaulia and subsequent colonization of the more northerly mountains. Of the remainder, S. teitensis, from the Teita Hills of Kenya, is sister taxon to the other species (which occur mainly in the Usambara Mts of north-east Tanzania). A group of nine Usambaran species that we call the 'ionantha complex' show minimal ITS genetic differentiation and are also taxonomically critical. Species diversity in the Usambara Mts appears to be the result of rapid, recent (possibly Pleistocene) radiation. This study reveals the limitations of ITS sequences for elucidating the radiation of poorly differentiated species (the ionantha complex). However, the molecular data strongly suggest that conservation of the Uluguru and Teita populations is essential for the protection of the full range of diversity within the genus.

Begonia x elatior plantlets which regenerated from leaf disk callus showed variations in plant morphology, number of flowers per plant, and flower size. Variations in flowering period, number of flowers per plant, and flower morphology were observed in Saintpaulia ionantha L. plants directly regenerated from leaf disk explants. The cytokinins, benzylaminopurine and zeatin, tested in the culture medium did not affect the basic plant characteristics including flower colour which remained stable in both species. Micropropagation of selected somaclones having the desirable trait of high number of flowers per plant was stable in the MV2 and MV3 generations.

Shoot organogenesis in African Violet was affected by factors including leaf age, wounding and leaf disc orientation. A gradient of regenerative potential was found among individual leaves on a plant. This regenerative potential was not directly proportional to the juvenility of leaf tissues. Wound treatment increased shoot organogenesis only when the wound was in direct contact with the medium, possibly by increasing nutrient and hormone uptake. Leaf disc orientation did not affect shoot number per disc but did determine the position of shoot organogenesis. Reduced gas exchange significantly reduced shoot production. This study also showed that adventitious roots originated from spongy mesophyll cells.

Recently, evidence has increased for both long- and short-distance transport of polyamines (PAs) in living organisms, but the mechanisms involved and physiological significance of PAs translocation are still not well understood. This review deals with various aspects of polyamine uptake and transport in higher plant tissues.

Phylogenetic relationships of eight species of Saintpaulia H. Wendl., 19 species of Streptocarpus Lindl. (representing all major growth forms within the genus), and two outgroups (Haberlea rhodopensis Friv., Chirita spadiciformis W. T. Wang) were examined using comparative nucleotide sequences from the two internal transcribed spacers (ITS) of nuclear ribosomal DNA. The length of the ITS 1 region ranged from 228 to 249 base pairs (bp) and the ITS 2 region from 196 to 245 bp. Pairwise sequence divergence across both spacers for ingroup and outgroup species ranged from 0 to 29%. Streptocarpus is not monophyletic, and Saintpaulia is nested within Streptocarpus subgenus Streptocarpella. Streptocarpus subgenus Streptocarpus is monophyletic. The ITS sequence data demonstrate that the unifoliate Streptocarpus species form a clade, and are also characterized by a unique 47-bp deletion in ITS 2. The results strongly support the monophyly of (1) Saintpaulia, and (2) Saintpaulia plus the African members of the subgenus Streptocarpella of Streptocarpus. The data suggest the evolution of Saintpaulia from Streptocarpus subgenus Streptocarpella. The differences in flower and vegetative characters are probably due to ecological adaptation leading to a relatively rapid radiation of Saintpaulia.

Yellow or brown spots (‘leaf spot’) often occur on Saintpaulia ( S. ionantha Wendl cv. Ritali) leaves. Leaf spot has been known to be caused by a rapid temperature drop created overhead irrigation. The sensitivity of Saintpaulia leaves to a temperature drop was investigated at intervals during the day/night cycle. In both a plastic house and a growth chamber, leaf spot sensitivity was highest during the dark period and decreased rapidly from the beginning of a light period, leading to the lowest level 4 h later. Leaf spot sensitivity was greatly influenced by environmental factors such as light, temperature, and humidity, among which light was the most important factor. After a dark period of 12 h, light reduced the sensitivity greatly within 4 h of exposure, and the resumption of dark conditions brought a large increase in the sensitivity within 2 h.

The relation between radical production and acute morphological changes of palisade cells of Saintpaulia induced by a rapid drop in leaf temperature was investigated. The drastic and apoptotic changes were observed immediately after the chilling treatment for 3 sec. OH radical production occurred immediately after the chilling treatment and then increased linearly depending on the time. The radical production might initiate and develop acute irreversible morphological changes resulting in apoptotic cell death of Saintpaulia palisade cells.