Botanical Studies最新文献

Background: Gastrodia elata is a fully mycoheterotrophic orchid and has long been used in traditional Chinese medicine. The life cycle of G. elata requires an association with two different fungi-Mycena for seed germination and Armillaria for tuber growth. The association with Armillaria is representative of the phytophagous type of orchid mycorrhiza: the intracellular hyphae are lysed without forming condensed pelotons. However, whether the association with Mycena during seed germination belongs to the same type of orchid mycorrhiza is unknown.

Results: Histological and ultrastructural studies revealed several notable features in different developmental stages. First, a thickened cell wall with papillae-like structures appeared during fungal penetration in the suspensor end cell, epidermal cells and cortical cells of germinating embryos. In addition, the formation of two distinctive cell types in the colonized region of a protocorm (i.e., the passage canal cell filled with actively growing fungal hyphae) can be observed in the epidermal cell, and the distinctive digestion cell with a dense cytoplasm appears in the cortex. Finally, within the digestion cell, numerous electron-dense tubules form a radial system and attach to degrading fungal hyphae. The fungal hyphae appear to be digested through endocytosis.

Conclusions: The present study provides important structural evidence for the phytophagous type of orchid mycorrhiza in the symbiotic germination of G. elata with Mycena. This case demonstrates a particular nutrient transfer network between G. elata and its litter-decaying fungal partner.

Background: Hydraulically efficient xylem was evolved in the vascular plants as an apomorphy of the group. Main xylem components involved in water conduction are tracheid and vessel. Vessels, in which two ends are perforated, constituted major evolutionary innovation within vascular plants, presumably providing more efficient solute conduction. Not all vascular plants have vessels. In pteridophytes vessels are present only in seven genera. The contention lies regarding the presence and distribution of vessel in pteridophytes are the impulsive force of this investigation.

Methods: Tracheary elements are isolated following the standard maceration technique, then hand-razor cut longisections are passed through the aqueous alcohol grades and air-dried samples are placed on stub, sputter coated with gold and examined with SEM.

Results: Two thelypteroid ferns viz. Ampelopteris prolifera (Retz.) Copel. and Thelypteris interrupta (Willd.) K. Iwats. are having vessel elements in root, rhizome, stipe, rachis, primary vein/costa, root-rhizome and rhizome-petiole junction i.e. through entire vascular connection of the plant body though the vessel network is interrupted and joined with parenchyma at the end in some places. Presence of vessel elements in the costa of pteridophytic taxa is first time reported by this study. Vessel end-walls are obliquely placed (root, rhizome, and stipe) but oblique to horizontal orientation is noticed in the primary vein/costa. End-walls are with simple, intermediate and compound perforation plates observed through SEM imaging as well as with tissue specific stain. Studied taxa are grown either in terrestrial microclimate of two contrasting environments i.e. sun and shade (A. prolifera) or in open swampy land (T. interrupta) with moderate to highly disturbed places as rapid proliferating populations showing interpopulation variations of tracheary elements length-width(s) and vessel end-wall length-width(s).

Conclusion: Vessel elements are present throughout the entire vascular connections of the plant body of A. prolifera (Retz.) Copel. and T. interrupta (Willd.) K. Iwats. Interpopulation variation of tracheary elements length-width(s) and vessel end-wall length width(s) are noticed. Till date only seven genera of pteridophytes are reported for the presence of vessel and these two genera are the new addition with the previous.

Background: Orchids maintain a symbiotic relationship with mycorrhizal fungi in the lifecycle. Previous reports indicated that diverse mycobionts may have different roles during orchid growth and development. Although various mycorrhizal fungi have been isolated from Dendrobium roots and protocorms, little is known about their specific effects on seed germination and seedling growth. To understand the specific role of isolated fungal strains (i.e., Tulasnella and Sebacina), we used symbiotic culture to compare the effect of 6 fungal strains on seed germination and seedling growth of Dendrobium officinale, an important Chinese medicinal orchid.

Results: In symbiotic germination tests, 6 fungal strains (4 Tulasnella strains and 2 Sebacina strains) promoted seed germination with different efficiencies. Seeds inoculated with Tulasnella strains S6 and S7 conferred higher germination percentage and faster protocorm development than other fungal strains. In symbiotic cultures, seedlings inoculated with Sebacina strain S3 had optimal fresh and dry matter yield. Also, Tulasnella strains S6 and S7 promoted seedling growth with good fresh and dry matter yield. Sebacina strain S2 inoculation greatly enhanced root and tiller production and the content of total crude polysaccharides, although seedlings were smaller with less fresh and dry matter yield than other seedlings.

Conclusions: Tulasnella and Sebacina strains could promote seed germination and seedling growth of D. officinale with different efficiencies. Our results suggest a non-specific mycorrhizal association and development-dependent preference. Our data provide the basic knowledge for use of different fungal strains in conservation and/or production practices of D. officinale.

Background: Unintentional introgression from genetically modified (GM) oilseed rape (Brassica napus) to a relative is inevitable in the open field. A feasible and practical strategy for restricting the spread of GM offspring is to set a reasonable isolated distance between GM B. napus and the relatives. To define the isolated distance, a pollen donor/recipient pair is a prerequisite to conducting the field trial of pollen flow. However, because the cultivation of GM B. napus is prohibited in Taiwan, it is difficult to obtain relevant information. Thus, this study explored the morphological and genetic characteristics of five varieties of B. napus (donor), three varieties of B. rapa (recipient), and the 15 corresponding F₁ hybrids, aiming to construct phenotypic data and genetic variation data and to select the most appropriate pollen donor/recipient for future field trials of pollen flow.

Results: The genome size of all F₁ hybrids estimated using flow cytometry showed intermediate DNA content between B. napus and B. rapa varieties. Most of the F₁ hybrids had intermediate plant height and blooming period, and the rosette leaves type and colors resembled those of B. napus varieties. The results of sequence-related amplified polymorphism (SRAP) showed an average of 9.52 bands per primer combination and 67.87 polymorphic bands among the F₁ hybrid population. Similarity and cluster analyses revealed higher similarity between F₁ hybrids and B. napus varieties than between F₁ hybrids and B. rapa varieties. Furthermore, we identified a specific 1100-bp band (LOC106302894) in F₁ hybrids and B. napus varieties but not in B. rapa varieties.

Conclusions: The rosette leaves and the DNA marker LOC106302894 observed in F₁ hybrids are consistent phenotypic and genetic characteristics that can be used to identify the presence of unintentional hybridization from B. napus to B. rapa in Taiwan. Due to the prohibition of GM crop cultivation, the hybridization system of non-GM Brassica species in this study can be utilized as a mimic scheme to conduct pollen flow trials, thus facilitating the determination of the proper isolated distance.

Background: Both natural and human-induced disturbances are commonly responsible for an overall decrease of the world's seaweed. Along Japan's coastal areas, edible seaweed production has been decreasing for decades. In this study, a production-environmental suitability model to estimate the impacts of environmental factors on seaweed production was developed. The developed model not only estimates human-induced disturbances but also quantifies the impacts of environmental factors responsible for the decline of annual seaweed production. The model estimated the temporal variation in human-induced disturbances and the effects of environmental factors (i.e., rainfall, CO₂ concentrations, temperature, typhoons, solar radiation, water nutrient levels, and water quality) on edible seaweeds in Japan from 1985 to 2012.

Results: The environmental suitability for seaweed production in Japan was about 4.6 times greater in 1992 than in 2011, meanwhile as a result of human activities, human-induced disturbances of seaweed increased at a rate of 4.9 times faster during the period of 1998-2012 than the period of 1985-1997. The ratio of decreased production to decreased environmental suitability for seaweed production in Japan increased by 15.2% during the study years, which means that seaweed production has become more sensitive to environmental disturbances, including climatic factors and human activities in 1998-2012.

Conclusions: The results are novel in demonstrating temporal variations in the level of environmental suitability to seaweed production by using a simple mathematical model. The production-environmental suitability model successfully predicted seaweed production by reflecting the 28-year temporal variation of the observed seaweed production in Japan.

Background: Ice plant (Mesembryanthemum crystallinum L.) is a model plant for studying salt-tolerant mechanisms in higher plants. Many salt stress-responsive ice plant genes have been identified with molecular and biochemical approaches. However, no further functional characterization of these genes in host plant due to lack of easy and effective transformation protocols.

Results: To establish efficient transformation system of ice plants, three types of ice plant materials, hypocotyl-derived callus, aseptically-grown seedlings and pot-grown juvenile plants, were used to develop Agrobacterium-mediated transformation protocols. The highest transient transformation efficiency was with 5-day-old ice plant callus co-incubated with an Agrobacterium tumefaciens at 2.5 × 10⁹ cells mL^-1 for 48 h. The 3-day-old ice plant seedlings with root tip removed were successfully infected with A. tumefaciens or A. rhizogenes, and obtained 85% and 33-100% transient transformation rates, respectively. The transient transformation assays in ice plant callus and seedlings demonstrated that the concentrations of Agrobacteria, the durations of co-incubation time, and the plant growth stages were three important factors affecting the transient transformation efficiencies. Additionally, pot-grown juvenile plants were syringe-injected with two A. rhizogenes strains A8196 and NCPPB 1855, to establish transformed roots. After infections, ice plants were grown hydroponically and showed GUS expressions in transformed roots for 8 consecutive weeks.

Conclusions: Our Agrobacterium-mediated transformation protocols utilized hypocotyl-derived callus and seedlings as plant materials, which can be easily obtained in large quantity. The average successful transient transformation rates were about 2.4-3.0% with callus and 33.3-100.0% with seedlings. We also developed a rapid and efficient protocol to generate transgenic roots by A. rhizogenes infections without laborious and challenging tissue culture techniques. This protocol to establish composite ice plant system demonstrates excellent improvements in efficiency, efficacy, and ease of use over previous ice plant transformation protocols. These Agrobacterium-mediated transformation protocols can be versatile and efficient tools for exploring gene functions at cellular and organ levels of ice plants.

Background: Rice blast, caused by Magnaporthe oryzae, is an important rice disease occurring in all rice-growing areas. To manage blast disease effectively and in an environmentally friendly way, it is important to continually discover diverse resistant resources for breeding. In this study, genome-wide association study (GWAS) was used to map genes/loci resistant to rice blast in the open-access rice diversity panel 1 (RDP1), previously genotyped with a 44K single-nucleotide polymorphism array. Two geographically and genetically different M. oryzae isolates from Taiwan, D41-2 and 12YL-DL3-2, were used to challenge RDP1. Infected leaves were visually rated for lesion type (LT) and evaluated for proportion of diseased leaf area (%DLA) by image analysis software.

Results: A total of 32 quantitative trait loci (QTLs) were identified, including 6 from LT, 30 from DLA, and 4 from both LT and DLA. In all, 22 regions co-localized with previously reported resistance (R) genes and/or QTLs, including two cloned R genes, Pita and Ptr; 19 mapped R loci, and 20 QTLs. We identified 100 candidate genes encoding leucine-rich repeat-containing proteins, transcription factors, ubiquitination-related proteins, and peroxidases, among others, in the QTL intervals. Putative resistance and susceptibility haplotypes of the 32 QTL regions for each tested rice accessions were also determined.

Conclusions: By using Taiwanese M. oryzae isolates and image-based phenotyping for detailed GWAS, this study offers insights into the genetics underlying the natural variation of blast resistance in RDP1. The results can help facilitate the selection of desirable donors for gene/QTL validation and blast resistance breeding.

Encrustation and element content (Ca, Fe, K, Mg and P) of charophytes was studied along plant thalli to investigate the dependency of thallus age and site-specificity. Charophytes were collected from five sampling sites (Angersdorfer Teiche, Asche, Bruchwiesen, Krüselinsee and Lützlower See) which were distinct with respect to water chemistry. Furthermore, photosynthesis was measured to identify the physiological state of plants in habitat waters and with the addition of different ion concentrations (Ca²⁺, K⁺, Mg²⁺ and Na⁺). Age pattern on encrustation of charophytes was site-specific: carbonate content increased from the youngest to the oldest part (Angersdorfer Teiche), younger parts were less encrusted than older parts in Asche, Bruchwiesen and Krüselinsee, whereas encrustation in Lützlower See was the same along plants thallus. Charophytes showed species-specific encrustation in investigated sites. Encrustation of C. hispida in Angersdorfer Teiche was also as high as of individuals from hard-water lakes irrespective of 10.15 mS cm^-1 (salinity of 6.3). For species growing in Angersdorfer Teiche, K/Na content and photosynthesis was lowest when compared to other sites. Photosynthesis of charophytes was enhanced after the addition of KCl and adversely affected by CaCl₂, MgCl₂ and NaCl. In summary, it was shown that encrustation of charophytes in water sites with strong ion anomalies could be as high as in hard-water lakes. It is assumed that ion composition, rather than ion concentration of Na⁺, Mg²⁺ and SO₄^2-, impact on the encrustation of charophytes. The age pattern on encrustation in this study showed a strong site-specificity, whereas encrustation of charophytes was species-specific. Ion concentrations, either of habitats or actively added in laboratory measurements, impact on encrustation, element content and photosynthesis of charophytes.

Background: Three species of wintersweets: Chimonanthus salicifolius S. Y. Hu, Chimonanthus zhejiangensis M. C. Liu and Chimonanthus grammalus M. C. Liu are widely distributed in China. The three wintersweets belonging to the genus of Chimonanthus that can synthesize abundant terpenoids that are beneficial to human health. Their buds and leaves are traditional Chinese herb applied by the 'She' ethnic minority in southeast of China. Squalene is a multi-functional and ubiquitous triterpene in plants, which is biosynthesized by squalene synthase (SQS) using farnesyl diphosphate (FPP) as the substrate. The synthesis of squalene in wintersweet was not clearly. This work would provide us much help to further understand the terpene metabolism in wintersweet and its health function to people at phytochemistry and molecular levels.

Results: In this study, we identified squalene component in the extractions of leaves of three wintersweets and isolated SQS genes from leaf transcriptomes. The three SQSs were highly conservative, so CzSQS from C. zhejiangensis was just determined the enzymatic activity. The in vitro expressed CzSQS that deleted two transmembrane domains could catalyze FPP to generate squalene with the presence of NADPH and Mg²⁺.

Conclusions: The squalene was one of wintersweet leaves phytochemicals. The squalene synthases of three wintersweet plants were highly conserved. The CzSQS was capable to catalyze two FPP molecules to squalene.

Background: Sapria is a distinctive and narrowly host-specific holoparasitic genus belonging to the Rafflesiaceae. Sapria himalayana, rare throughout its range from NE India, SW China, Thailand to Vietnam, is a little-understood species first recorded for Vietnam in 1959, and only recollected there over half a century later in February 2017. This has facilitated an assessment of its taxonomic identity and our understanding of its morphology and natural history aspects.

Results: Six populations of Sapria at Vietnam's Tuyền Lâm Lake, and another two populations at the Nam Ban Protection Forest and the Cam Ly area were found, in an area of about 20 km in radius. Previously documented size attributes, morphological details and colour patterns allowed clear identification of the Vietnamese taxon as Sapria himalayana f. albovinosa. A full description of the species for Vietnam is provided. Past authors have distinguished the sexes by column form and structure, colour of the upper disk, details of the inner surface of the perigone tube, and presence of ovarial chambers below the column in the female. We present additional observations that male flowers consistently have more steeply held perigone lobes than females, in which the lobes were more spread out at wider angles in fully open flowers, and that males have a much lower cupule than females. The latter difference, especially, appears to be useful for quick determination of the sex even in the advanced floral bud stage. The host plant was the lianescent Tetrastigma laoticum (Vitaceae), but superficially it was not possible to ascertain the clonal relationship of neighbouring host lianas. Male and female flowers were found mixed together in the same cluster from one individual liana. Potential pollinators included Calliphorid and Stratiomyid flies observed visiting open flowers.

Conclusions: Our observations have added to an increased understanding of the morphology of this highly specialized parasitic life form. More than this, we have ascertained its occurrence in Vietnam, with information made available to authorities of the Lâm Đồng Province where our studies were conducted, for the sites to be specially demarcated for conservation and carefully managed tourism use.