Alyssum Montanum Research Articles

Genetic and morphological variation in the diploid–polyploid Alyssum montanum in Central Europe: taxonomic and evolutionary considerations

The genus Alyssum is one of the largest, yet least known genera of the Brassicaceae family. The present study focusses on the Central European populations of A. montanum, a species that is highly variable with respect to its morphology, ploidy levels and ecological requirements. This variation is naturally reflected in a number of recognised infraspecific taxa, and diverse opinions exist with regards to their value and circumscriptions. Based on amplified fragment length polymorphism (AFLP), as well as morphometric and flow-cytometric evidence, we demonstrate here that the variation patterns contradict the current taxonomic concepts held for this species. Our data support the division of the analysed populations into the following groupings: (i) the ‘core’ group that includes most of the Central European diploid and tetraploid populations; (ii) the diploid ‘Swiss–SW German’ group, also including the population from the type locality of A. montanum; (iii) the hexaploid A. montanum subsp. pluscanescens, a Slovenian and Croatian endemic suggested to be of hybrid origin; and (iv) the diploid ‘Serbian’ group from the sand dunes of Deliblatska Pescara. A. repens, represented by a diploid population from Austria and tetraploid populations from Romania, is confirmed to be distinct from A. montanum. On the other hand, we suggest rejecting the recognition of A. montanum subsp. brymii, an assumed endemic of Slovakia and Hungary, and A. montanum subsp. montanum and subsp. gmelinii in their traditional circumscriptions.

Three new phylogenetic lineages are the closest relatives of the widespread species Albugo candida

White blister rust caused by the obligate biotroph Albugo candida ( Albuginaceae; Oomycota) is one of the most notorious and common diseases of Brassicaceae. During the past 5 y, A. candida specimens collected from about 30 host genera were phylogenetically and morphologically investigated in several studies. These not only revealed that A. candida s.str. has a broad host range, encompassing a large number of host plants belonging to Brassicales, but also the presence of previously overlooked species of Albugo with hosts in this order. In this study, we examined specimens from Alyssum, Barbarea, and Rorippa, of which many species were commonly recorded as host plants of A. candida but could not be included in previous works due to the paucity of specimens available. It was revealed that Albugo specimens from Alyssum montanum, Barbarea vulgaris, and various Rorippa species, were placed in three phylogenetically distinct clades, but closer to A. candida s.str. than any previously reported species. Oospores were observed from Albugo specimens parasitic to Rorippa and could be distinguished morphologically from A. candida. Therefore, Albugo rorippae sp. nov. is described and illustrated here. In addition, a key of Albugo species described previously from Brassicales is given. The present study reveals that a large number of Albugo species remain still undiscovered, and that species close to A. candida exist. This could help elucidating the basis of the broad host range of A. candida as opposed to the narrow specialisation that is seemingly present in other species of Albugo on the Brassicaceae.

(1993) Proposal to conserve the name Alyssum montanum (Cruciferae) with a conserved type

basal ovule. As a result of the differing geographical focus of the two revisions, none of the Monoon species recognised by Miquel was specifically included in Polyalthia sect. Monoon by Hooker & Thomson, although it is clear that the latter authors’ application of the sectional name corresponds with the species group that includes M. canangioides (Zoll.) Miq. (= P. canangioides (Zoll.) Boerl.) and M. lateriflorum (Blume) Miq. (= P. lateriflora (Blume) King), which only have one ovule per carpel. Although the name Monoon has very rarely been used at the generic level, several authors have followed Hooker & Thomson in recognising it as a section within Polyalthia (e.g., Fries in Melchior, Nat. Pflanzenfam. 17a II: 1–171. 1959; Sinclair in Gard. Bull. Singapore 14: 149–516. 1955; Van Heusden in Blumea, suppl. 7: 1–218. 1992). In order to maintain consistency of the application of the name Monoon for those species with a single ovule per carpel (as recommended by Mols & al. in Syst. Bot. 33: 490–494. 2008), we have opted to typify the generic name using M. lateriflorum, a species currently known as P. lateriflora. The name Enicosanthum was first validly published by Beccari (l.c.) with the description of E. paradoxum Becc. as the only included species name and hence the type. Thus far 20 names have been published in the genus (IPNI, l.c.), of which 18 are currently accepted (Annonaceae checklist, l.c.). Molecular phylogenetic research has indicated that several sampled Polyalthia species, including P. lateriflora, form a well-supported clade with all sampled Enicosanthum species (Mols & al., l.c. 2004; Xue & al., l.c.). In order to ensure recognition of strictly monophyletic genera, we intend to recognise all the species in this clade under the same generic name, which will unavoidably necessitate the renaming of a large number of species currently classified in Polyalthia. With our lectotypification, application of the principle of priority would require all species in this clade to be recognised under the generic name Monoon; this would require not only the renaming of many Polyalthia species, but also the transfer of all 18 Enicosanthum species. The name Enicosanthum has been very extensively used (e.g., Fries, l.c.; Sinclair, l.c.; Walker in Contr. Gray Herb. 202: 1–131. 1971; Klucking, Leaf Venation Patterns, vol. 1, Annonaceae, 1986; Van Heusden, l.c.; Van Setten & Koek-Noorman in Biblioth. Bot. 142: 1–101 + pl. 1–50. 1992). Conservation of the name Enicosanthum is therefore proposed, enabling its continued use and avoiding the unnecessary loss of a long-established and widely used generic name.

A Comparative Study of Germination Biology and Plant Performance in Two Dry Grassland Species

Over the last 20 years, the species assemblage of the species-rich dry grassland communities of central Germany has changed due to the ongoing abandonment of traditional land-use practices. In our study we wanted to investigate the germination biology and the plant-plant interaction of the low-growing and declining forb Alyssum montanum and the increasingly dominant grass Festuca rupicola. To investigate the germination behaviour we simulated cold (8/4°C), warm (20/10°C) and hot (32/20°C) conditions under a light-dark regime (12/12 hours) as well as in constant darkness. Germination of both species was similar with almost all non-dormant seeds germinating under intermediate temperature conditions (20/10°C). Whereas F. rupicola (F) germinated equally well under light changing conditions and constant darkness, the germination of A. montanum (A) was clearly reduced in darkness, which implies a strong competitive advantage of F. rupicola in dense vegetation cover. However, A. montanum germinated early under all temperatures regimes and better under 20/10°C as well as with light changing conditions. The interactions between the two species were tested in a pod-experiment with a replacement design, within which the composition of individuals was changed in the following way: 4A/1F, 3A/2F, 2A/3F, 1A/4F (eight replications per each). To evaluate any influence of intraspecific competition we created monocultures in an additive design (1A, 2A, 3A, 4A, 5A, 1F, 5F; eight replications per each). Despite that A. montanum developed faster and flowered after only four months in the replacement design experiment, the herb responded negatively to the presence of F. rupicola in several parameters (number of flowers, number of fruits and biomass per individual). The calculation of the Relative Neighbour Effect (RNE) indicated facilitation for F. rupicola and competition on A. montanum, which increased with increasing number of individuals of the other species. Our data suggest that A. montanum seedling recruitment, growth and fitness are negatively affected by increasing vegetation density of the expanding grass species F. rupicola.

The role of free histidine in xylem loading of nickel in Alyssum lesbiacum and Brassica juncea.

Exposure of the hyperaccumulator Alyssum lesbiacum to nickel (Ni) is known to result in a dose-dependent increase in xylem sap concentrations of Ni and the chelator free histidine (His). Addition of equimolar concentrations of exogenous L-His to an Ni-amended hydroponic rooting medium enhances Ni flux into the xylem in the nonaccumulator Alyssum montanum, and, as reported here, in Brassica juncea L. cv Vitasso. In B. juncea, reducing the entry of L-His into the root by supplying D-His instead of L-His, or L-His in the presence of a 10-fold excess of L-alanine, did not affect root Ni uptake, but reduced Ni release into the xylem. Compared with B. juncea, root His concentrations were constitutively about 4.4-fold higher in A. lesbiacum, and did not increase within 9 h of exposure to Ni. Cycloheximide did not affect root His or Ni concentrations, but strongly decreased the release of His and Ni from the root into the xylem of A. lesbiacum, whereas xylem sap concentrations of Ca and Mg remained unaffected. Near-quantitative chelation of Ni with nitrilotriacetate in the rooting medium did not enhance Ni flux into the xylem of A. lesbiacum and B. juncea, suggesting the absence of a significant apoplastic pathway for Ni entry into the xylem. The data suggest that in B. juncea roots, Ni(2+) uptake is independent of simultaneous uptake of His. In both species, enhanced release of Ni into the xylem is associated with concurrent release of His from an increased root free His pool.

Effect of copper on germination and seedling growth ofMinuartia, Silene, Alyssum andThlaspi

The influence of increasing copper concentrations on seed germination, seedling survival and radicle length ofMinuartia hirsuta, Silene compacta, Alyssum montanum andThlaspi ochroleucum was studied. Seed germination was highly affected by the higher Cu2+ concentrations (80 and 160 μM), while lower Cu2+ concentrations seemed to be necessary for seed germination, even for the plants originated from non-Cu2+-rich soils (i.e. A. montanum). Nevertheless, plants originated from Cu2+-rich soils (M. hirsuta, S. compacta) showed a higher demand of Cu2+ for rapid seed germination. Cu2+ at higher concentrations severely reduced growth rate of radicle, especially inA. montanum andT. ochroleucum. These data clearly indicate the reduced suitability of the above mentioned plant species for reclamation on Cu2+ soils. Lower Cu2+-concentrations had no influence on seedling survival inM. hirsuta andS. compacta, but a progressive reduction of a number of survived seedlings with increasing Cu2+ concentration was found, that was more pronounced inA. montanum andT. ochroleucum.

Copper-induced changes on growth, metal content and photosynthetic function of Alyssum montanum L. plants

The response of root systems of Alyssum montanum to increasing Cu levels was studied. Changes in chlorophyll and metal content and in photosynthetic function were also investigated. Low Cu concentrations in the nutrient solution did not affect root elongation, possibly due to the development of co-tolerance to Cu since the plants are tolerant to Zn and Pb. However, with higher Cu concentrations the extension of the root and the chlorophyll content declined sharply. Roots accumulated higher amounts of Cu than shoot-leaves at all Cu treatments. High Cu contents in plant tissues also negatively influenced uptake and translocation of Ca, Mg, Fe and K in roots and above-ground parts. In addition, excess Cu application was accompanied by a marked decline in the variable fluorescence and a retardation of the electron transfer in PSII, indicating an inhibitory site on the photooxidizing side of PSII. The decreased photochemistry activity of PSII suggests a decrease in the efficiency of the reduction of the primary electron acceptor and reflects damage to the donor and acceptor side of PSII. An absence of the intermediate transient at the slow part of the fluorescence induction kinetics and a dramatic decrease of the (F P-F S)/F S ratio were also observed under Cu treatments. The photosynthetic function of A. montanum seemed to be affected more than root growth and chlorophyll content under Cu stress.

Photoacoustic measurements of photosynthetic activities in intact leaves under copper stress

Photoacoustic spectroscopy was used to monitor Cu damage to photosynthesis by measuring photochemical energy storage (PES) at high frequency of 600 Hz and yield of O 2 evolution (Aox/Apt) at low frequency of 19 Hz in intact leaves of a Cu-tolerant ( Silene compacta) and a non-Cu-tolerant ( Alyssum montanum) species. The results indicated that Cu affected root growth (RRG), more severely than photoacoustic parameters in both species. Plants of S. compacta grown in lower Cu concentration revealed an enhancement phenomenon on RRG, PES and Aox/Apt, in contrast, plants of A. montanum revealed a slight decrease in the above mentioned parameters. A remarkable decline of PES and Aox/Apt for both species, was observed, at higher Cu concentrations, a fact considered to reflect inhibition of the photsynthetic e − flow in thylakoids. PES was less affected by Cu stress than O 2 evolution showing a differential sensitivity of two photosystems in Cu. Photosystem II (PSII) seemed to be more sensitive because of degradation and leakage of chloroplasts membranes, inducing a decline in yield of O 2 evolution. On the other hand, PES was appreciable because of cyclic e − transfer around the intact or less inhibited photosystem I (PSI).