New and noteworthy species in Begonia section Gireoudia (Begoniaceae) from Mexico

Two new species are described inBegonia sectionGireoudia:B. rafael-torresii andB. mariti.Begonia karwinskyana, known previously only from its type, is described more amply and discussed.     

Studies on Middle American begonia (Begoniaceae) II

Begonia breedlovei, B. chiapensis, andB. jaliscana, new species in sectionGireoudia from Mexico, are described, illustrated, and discussed.     

Presence and Possible Mode of Action of a Proteinaceous Gonadotropin-like Growth Regulating Factor in Plant Systems

Antiserum to human chorionic gonadotropin (HCG) caused marked inhibition of adventitious rooting of Begonia semperflorens and Chrysanthemum morifolium stem cuttings. Immuno-absorption of crude protein extract from chrysanthemum foliage through a column of polymerized and unsolubilized HCG antibodies resulted in a significant reduction in adventitious root promoting activity of the extract. These results are discussed in the light of a hypothesis that an endogenous protein growth regulating substance which immunologically resembles HCG exists in plant systems. Further experimentation with HCG suggests that its mode of action is possibly via the regulation of peroxidase enzymatic control of auxin levels.     

Genetic differentiation and species cohesion in two widespread Central American Begonia species

Begonia is one of the ten largest plant genera, with over 1500 species. This high species richness may in part be explained by weak species cohesion, which has allowed speciation by divergence in allopatry. In this study, we investigate species cohesion in the widespread Central American Begonia heracleifolia and Begonia nelumbiifolia, by genotyping populations at microsatellite loci. We then test for post-zygotic reproductive barriers using experimental crosses, and assess whether sterility barriers are related to intraspecific changes in genome size, indicating major genome restructuring between isolated populations. Strong population substructure was found for B. heracleifolia (F_ST=0.364, F′_ST=0.506) and B. nelumbiifolia (F_ST=0.277, F′_ST=0.439), and Bayesian admixture analysis supports the division of most populations into discrete genetic clusters. Moderate levels of inferred selfing (B. heracleifolia s=0.40, B. nelumbiifolia s=0.62) and dispersal limitation are likely to have contributed to significant genetic differentiation (B. heracleifolia Jost''s D=0.274; B. nelumbiifolia D=0.294). Interpopulation crosses involving a divergent B. heracleifolia population with a genome size ∼10% larger than the species mean had a ∼20% reduction in pollen viability compared with other outcrosses, supporting reproductive isolation being polymorphic within the species. The population genetic data suggest that Begonia populations are only weakly connected by gene flow, allowing reproductive barriers to accumulate between the most isolated populations. This supports allopatric divergence in situ being the precursor of speciation in Begonia, and may also be a common speciation mechanism in other tropical herbaceous plant groups.     

Begonia baik and B. padawanensis spp. nov. (Begoniaceae) from sandstone areas in Sarawak,Malaysia

Two new species of Begonia (Begoniaceae), B. baik and B. padawanensis, from Sarawak are described and illustrated. Begonia baik, a member of sect. Petermannia, resembles B. conipila, but is distinguishable by having glabrous ovary (vs sparsely hispid) and margins of bracts dentate and glandular hairy (vs entire). Begonia padawanensis (sect. Reichenheimia) is similar to B. andersonii, differing in the leaves being obtriangular‐spatulate (vs orbicular) and having 5 pistillate flower tepals (vs 4). Both new species were discovered in a sandstone area in Padawan, Sarawak.     

Effect of ultraviolet light on stomatal movement

Byl pozorován uzávěr pr?duch? uBegonia semperflorens během několika minut po ozá?ení UV.     

Agrobacterium tumefaciens-mediated transformation of Elatior Begonia (Begonia×hiemalis Fotsch)

We report a method for Agrobacterium-mediated transformation of Elatior Begonia (Begonia×hiemalis Fotsch). Young leaf discs were infected with Agrobacterium tumefaciens strains AGL0 and LBA4404. Each strain has a binary vector plasmid, pIG121Hm that includes the β-glucuronidase (GUS) gene with an intron as a reporter gene, and both the neomycin phosphotransferase II and the hygromycin phosphotransferase genes as selection markers. Explants were cultured on modified MS medium supplemented with 1.0 mg/l BA, 0.5 mg/l IAA, 300 mg/l ticarcillin, and either 100 mg/l kanamycin and 5 mg/l hygromycin, or 300 mg/l kanamycin for selection and regeneration. Out of 500 explants infected with AGL0, 16 plantlets were regenerated, and out of 628 explants infected with LBA4404, two plantlets were regenerated after 4 months of culture. Transformation was confirmed by Southern blot analysis of the GUS gene and by histochemical assays of GUS activity in plant tissues. Ten in vitro transgenic plants were obtained from AGL0 infected explants only.     

A rapid leaf-disc sampler for psychrometric water potential measurements

An instrument was designed which facilitates faster and more accurate sampling of leaf discs for psychrometric water potential measurements. The instrument consists of an aluminum housing, a spring-loaded plunger, and a modified brass-plated cork borer. The leaf-disc sampler was compared with the conventional method of sampling discs for measurement of leaf water potential with thermocouple psychrometers on a range of plant material including Gossypium hirsutum L., Zea mays L., and Begonia rex-cultorum L. The new sampler permitted a leaf disc to be excised and inserted into the psychrometer sample chamber in less than 7 seconds, which was more than twice as fast as the conventional method. This resulted in more accurate determinations of leaf water potential due to reduced evaporative water losses. The leaf-disc sampler also significantly reduced sample variability between individual measurements. This instrument can be used for many other laboratory and field measurements that necessitate leaf disc sampling.     

Two New Records of Begonia L. (Begoniaceae) from China

Two species of Begonia L. (Begoniaceae), viz. Begonia demissa Craib and Begonia subperfoliata Parish ex Kurz are reported as new records in China, and the two species assigned to Begonia sect. Parvibegonia A. DC. and Begonia sect. Diploclinium (Wight) A. DC. respectively. The type locality of Begonia demissa is in Thailand and of Begonia subperfoliata in Myanmar. The distribution of Begonia demissa is now extended to Mengyuan, Mengla County of Xishuangbanna Dai Autonomous Prefecture and that of Begonia subperfoliata to Liushun Community, Pu’er City, both in Yunnan province, China.     

Physiological dormancy in seeds of two endemic species of Begonia from Yunnan Province,China: diagnosis and classification

With the purpose of assessing the status of dormancy in seeds of two Begonia species (Begonia lithophila and Begonia guishanensis), freshly matured seeds were given gibberellic acid and moist chilling and allowed to dry after ripening. The seeds were then germinated on media with or without KNO₃ at 15, 20, 25, 30 and 18/25°C. All three treatments significantly increased germination percentages. Examination by X‐ray revealed that seeds of both species have a fully developed embryo and thus have no morphological component of dormancy; seeds readily imbibed water and KNO₃ solution. Therefore, we conclude that seeds of the two Begonia species have non‐deep physiological dormancy. Although KNO₃ significantly increased germination in both species, alternating temperatures did not, suggesting that the most favorable microhabitat for germination is small‐scale disturbances under the forest canopy.     

云南秋海棠属植物有性杂交特性

通过云南秋海棠属植物属下5个系统分类组的种类及外来园艺品种共109个组合的有性杂交试验,以系统分类组合、园艺分类组合(不同茎的形态类型组合)分别进行方差分析。结果表明:云南秋海棠属植物属下等级的系统分类组内、组间的有性杂交,以及不同茎的形态类型的有性杂交均无显著差异,亲和力较强而可育性高,可在云南秋海棠属植物属内进行广泛地远缘杂交; 云南产秋海棠属植物原种与外来园艺品种间的有性杂交亲和性弱而可育性低,需选择花粉粒和胚囊正常发育的外来园艺品种大量杂交,并采用切实可行的技术措施克服远缘杂交不育,以期培育新颖奇特的秋海棠属植物新品种。     

Effects of Oxygen and Respiratory Inhibitors on Induction and Release of Dormancy in Aerial Tubers of Begonia evansiana

Effects of O₂ and some respiratory inhibitors on the induction and release of bud dormancy were examined with the aerial tubers of different ages of Begonia evansiana Andr. Oxygen was needed not only for tuber sprouting but also during the chilling process at 2 to 5 C to break tuber dormancy. If the mature tubers were exposed to blue light during the chilling period, their dormancy was strikingly released even by the chilling given under an O₂ concentration as low as 3%. Blue light pretreatment promoted photo-sprouting of immature tubers only when given under lower O₂ concentrations. On the other hand, red light became effective in inducing dormancy in the immature tubers and in prolonging dormancy in the mature tubers as O₂ tension was increased. This was also the case with the induction of dormancy in the immature tubers by exposing them to a lower temperature (17 C) in the dark. The development of dormancy was suppressed by 2,4-dinitrophenol, p-nitrophenol, and sodium azide.     

Hormonal Regulation of Pedicel Abscission in Begonia Flower Buds

In order to analyse the hormonal regulation of flower bud shedding in Begonia, levels of indoleacetic acid (IAA), abscisic acid (ABA) and ethylene were determined in buds and pedicels. The translocation and metabolism of ¹⁴C-labeled IAA in pedicel segments were also studied. In a monoecious Begonia fuchsioides hybrid, abscising male flower buds contain about 1% of the IAA present in non-abscising female flowers. In a male Begonia davisii hybrid, the seasonal variation in bud drop coincides with changes in the IAA content of the buds, while also the release of IAA from the bud to the pedicel is hampered. Abscission zones of these pedicels always contain abscission promoting ethylene concentrations. The tissue is prevented from responding with abscission by IAA from the flower buds. The buds also contain ABA but without influencing abscission considerably. Pretreatment with ethylene or ABA does not affect IAA transport in pedicel segments. The rate of this transport is 4–6 mm × h^–1:; the capacity increases with the transverse area. In young segments, IAA is decarboxylated and also otherwise metabolized.     

Transcriptome analysis reveals anthocyanin acts as a protectant in <Emphasis Type="Italic">Begonia semperflorens</Emphasis> under low temperature

Anthocyanins are natural bioactive pigments in plants that play important roles in many physiological functions. They are found in various tissues and can protect plants against different stress conditions. Anthocyanins are synthesized and accumulate in nutritional organs, which is crucial for plants to adapt to and resist adverse environmental conditions, including high exposure to light, ultraviolet light, low temperatures, drought, pests and disease. Some progress has been made in understanding the adaptability of anthocyanin to the external environment. Begonia semperflorens is an excellent model for studying the function and regulation of anthocyanin synthesis. To investigate the biosynthesis and regulation of anthocyanins, RNA sequencing techniques were employed to investigate anthocyanin biosynthesis induced by low temperature in B. semperflorens leaves. A total of 74,779 unigenes with a mean length of 1249 bp were assembled. Functional annotations were implemented using five protein databases. Differentially expressed genes involved in the process of anthocyanin biosynthesis were identified. This study represents the first report of a broad-scale gene expression study on B. semperflorens.     

Three new species of begonia (Begoniaceae) from Mexico

Begonia lyniceorum, B. multistaminea andB. sousae from the state of Veracruz in Mexico are described as new, illustrated and discussed.     

Rapid Changes in Cell Wall Yielding of Elongating Begonia argenteo-guttata L. Leaves in Response to Changes in Plant Water Status

Elongation and epidermal cell turgor (P) of Begonia argenteoguttata L. leaves were simultaneously measured to determine the wall-yielding behavior of growing leaf cells in response to changes in plant water status. Rapid changes in plant water status were imposed by irrigating the rooting media with solutions of −0.20 and −0.30 MPa mannitol. These treatments caused decreases in P of 0.09 and 0.17 MPa, respectively. The decreases in P were complete within 10 min, and P did not change thereafter. Following treatments, leaf elongation was nil for periods of 25 to 38 min. Subsequently, elongation recovered to steady rates that were 45 or 75% lower than in the well-watered controls. Leaves of plants that were pretreated with −0.30 MPa of mannitol and rewatered showed an increase in P of 0.19 MPa, which was complete within 15 min; P did not change thereafter. Rewatering caused a several-fold increase in leaf elongation rates, which subsequently declined while P was increasing, to reach steady rates similar to that of the controls. Several estimates of elastic deformation indicated that most of the elongation responses to altered P were due to changes in irreversible deformation. The results showed that the initial effects of changes in P on leaf elongation were partially compensated for by changes in the cell wall-yielding properties. We conclude that linear relationships between P and adjusted growth rates are not necessarily indicative of constant wall-yielding properties. Instead, these relationships may reflect the effect of P on wall-loosening processes.