Stem structure strongly influences the drought response across a diverse group of temperate and tropical tree species. The stem of Salvadora persica (miswak), used as a chewing stick in the Islamic world, has a number of distinctive xeromorphic characteristics adapting it to arid or semi-arid conditions. The thick periderm is interrupted at points around the stem by transversely oriented lenticels to moderate exchange of vital gases. On the stem surface are 3-dimensional epicuticular crystals of various shape and size, present to protect against UV exposure, insects and pathogens. The secondary xylem contains groups of xylem fibers which consist of thickwalled narrow cells. Vessels are axially oriented without branching for interconnection. The xylem is also composed of parenchyma cells, which are characterized as ray parenchyma and wood parenchyma. The woodparenchyma become crushed in the middle, forming a chamber which is later filled with amorphous inclusions or rhombohedral crystals. SEM-EDX analysis revealed sulphur in wood parenchyma cells, likely a defense against pathogenic microorganisms. Apart from its adaptive value, the sophisticated stem anatomy of Salvadora persica, in combination with its chemistry, makes it an effective tool for oral hygiene.
This paper is both a review and a study. It discusses the taxonomic status of Yellow Archangel (Galeobdolon luteum Huds.) from historical and contemporary perspectives, and gives a comprehensive list of synonyms for the discussed genera, species and lower taxonomic units, including their publication details. In the study it is postulated that G. luteum should be included in the genus Lamium. The hypothesis is verified by a comparative analysis between the representatives of the genera Galeobdolon and Lamium in four DNA regions: ITS, accD, rpoC1 and trnH-psbA. The analysis supported the determination of phylogenetic relationships among the studied taxa: G. luteum is not genetically distant enough from Lamium to be considered a separate genus, and integration of Galeobdolon and Lamium is legitimate.
This study used ISSR markers to assess the genetic diversity of a collection of 15 genotypes of Salix purpurea and 6 interspecific hybrids, employing 40 of 60 tested ISSR primers generating polymorphic amplification products. The PCR-ISSR method was adapted for S. purpurea by optimizing the annealing temperature for each primer. The polymorphism index of ISSR amplification products was 91.8% for all studied genotypes and 70.4% for S. purpurea genotypes. Nei's genetic identity statistics ranged from 0.538 to 0.958. Nei's genetic distance values were used to build a dendrogram (UPGMA) for the investigated genotypes. The dendrogram shows five clusters, and principal coordinate analysis yielded nearly the same genetic relationships among the studied genotypes. The results confirm the usefulness of ISSR markers for determining genetic diversity in S. purpurea.
An effective procedure for producing transformed Centaurium erythraea plants from synthetic seeds is described. Explants were encapsulated in 3% sodium alginate with 3% sucrose. Encapsulated hairy roots were cultured on half-strength Murashige and Skoog (1/2 MS) or Woody Plant (WPM) agar-solidified regeneration media supplemented with 6-benzylaminopurine (BAP) or without the cytokinin. The use of WPM with 0.5 mg/L of BAP gave the best shoot formation frequency (86%) and mean number of shoots (15) per root segment. Shoots rooted with 97% frequency on 1/2 MS without growth regulators. Encapsulated shoot buds were cultured on onethird- strength MS agar medium (1/3 MS) supplemented with indole-3-butyric acid (IBA) (0.05 mg/L). The plantlet conversion frequency was 32%. The encapsulated hairy roots and shoot buds were stored for 4, 6 or 14 weeks at 4°C. Synthetic seeds encapsulated with 3% sodium alginate with 3% sucrose stored at 4°C remained viable for 6 weeks but their developmental parameters significantly decreased. Adding nutrient medium and growth regulator to the alginate matrix increased plantlet recovery from both non-stored and stored synthetic seeds: synthetic seeds retained their viability and ability to form plantlets even after 14 weeks of storage. Regenerated transformed plantlets of C. erythraea were acclimatized in the greenhouse.
The study examined changes in lysine decarboxylase (LDC), ornithine decarboxylase (ODC) and tyrosine decarboxylase (TyDC) activity in tissues of pea (Pisum sativum L.) infested by the pea aphid (Acyrthosiphon pisum Harris). The aphid induced increased ODC activity after one day and at two weeks. The effect was clearly systemic. TyDC activity increased after one day and at one week at feeding sites (aerial parts), while LDC activity increased only after one day of infestation and then decreased. Attack by aphids also affected enzyme activity in root tissues not directly damaged by the herbivores. The mechanisms of the response induced by pea aphid infestation in pea are discussed.
We measured the total chlorophyll (Chl a+b) content in seedling leaves of fifteen maize cultivars infested by two studied aphid species (oligophagous Rhopalosiphum padi L., monophagous Sitobion avenae F.) 7 and 14 days after the beginning of infestation, using a SPAD-502 chlorophyll meter. Chlorophyll loss was more severe in R. padi-infested than in S. avenae-infested plants. Chlorophyll depletion was greater after long-term (14 days) than after short-term aphid infestation in the investigated host systems. Seedlings of Złota Karłowa and Tasty Sweet were more damaged by aphid feeding; Ambrozja and Płomyk plants were less damaged by aphid feeding.
Isatis cappadocica Desv. is a newly found As-hyperaccumulator showing very high remediation efficiency in polluted soils. We studied the effects of arsenic at 0-1400 μM concentrations on seed germination, relative root length, relative shoot height, and root and shoot biomass in young seedlings of I. cappadocica. The seeds were from Iranian arsenic-contaminated mine spoils and from a non-contaminated population. The control for reference was brassica (Descurenia sofia). Germination decreased significantly versus the control with increasing arsenic concentrations. The response to arsenic exposure differed between the I. cappadocica populations and D. sofia. I. cappadocica from mine spoil seeds showed strong resistance to the highest As concentration, with no adverse effects until the 1000 μM dose. Germination from non-mine seeds of I. cappadocica decreased to 89.6% at 1400 μM As. D. sofia germination was completely inhibited at 400 μM As. Relative root length (RRL) and relative shoot height (RSH) decreased with increasing As concentration. Overall, RRL correlated with RSH. Shoot height and root length were more sensitive to arsenic than other endpoints, and might be used as arsenic toxicity indicators. I. cappadocica showed more As tolerance than the reference brassica.
It has long been observed that toxic heavy metals at different concentrations can induce root hair development in plants. In oilseed rape we studied ethylene levels and root hair initiation under Cd2+ stress. Growth of the primary root was inhibited but close to root tips the development of subapical root hairs was significantly stimulated by Cd2+ at 30 μM. Versus the control, the distance between the root tip and the root hair zone and the length of the epidermal cell in the elongation zone were significantly reduced by Cd2+ at the same concentration. Exogenous application of Cd2+ and 1-aminocyclopropane-1-carboxylate (ACC) to roots had similar effects on subapical root hair development. Hair density increase and hair elongation in the presence of Cd2+ were reduced by the ethylene inhibitors CoCl2 at 15 μM and aminooxyacetic acid (AOA) at 10 μM. Exposing roots to Cd2+ caused a rapid increase in superoxide radical (O2 ·-) production in the root hair differentiation zone, and at the tips of emerging and newly formed root hairs. Cd2+-induced O2 ·- production at the growing hair tips was blocked in the presence of AOA. Our findings suggest that Cd2+-induced ethylene signaling may act upstream of O2 ·-. Cd2+ promotion of O2 ·- production may operate through an ethylene signaling pathway, and O2 ·- itself may stimulate root hair elongation.
The Crassulaceae family mainly comprises herbaceous leaf succulents, some of which are used as ornamentals. The development of the embryo suspensor in Sedum reflexum L. was investigated using cytochemical methods, light and electron microscopy. The full development and functioning of the suspensor occurs during the late globular and heart-stage embryos. The suspensor consists of a large basal cell and a single row of 6-10 chalazal cells. The basal cell produces a branched haustorium which invades ovular tissues. The walls of the haustorium and the micropylar part of the basal cell form the wall ingrowths that are typical for transfer cells. The dense cytoplasm filling the basal cell is rich in profiles of endoplasmic reticulum, active dictyosomes, mitochondria, plastids, microtubules, bundles of microfilaments, microbodies and lipid droplets. The present work reveals that the suspensor structure in S. reflexum markedly differs from that found in other representatives of Crassulaceae. Ultrastructural analysis and cytochemical tests (including proteins, insoluble polysaccharides and lipids) indicate that in S. reflexum the embryo suspensor is involved mainly in absorption and transport of metabolites from the ovular tissues to the developing embryo proper via the chalazal suspensor cells.
cAMP is a second messenger which plays a regulatory role in a wide variety of biological processes in organisms ranging from prokaryotes to higher eukaryotes, but knowledge of its role in macroalgae and vascular plants is limited. We modified cAMP levels in the macroalga Chara vulgaris thallus and studied the effects on thallus growth and gametangia development: db-cAMP (permeable analog of cAMP), adenylate cyclase (AC) activator, forskolin and theophylline (cAMP phosphodiesterase (PDE) inhibitor) were used to elevate cAMP levels, and the AC inhibitors 2'-dAdo and 2'-d3'-AMP were used to decrease them. The results suggest that in Chara vulgaris the cAMP pathway may regulate both vegetative thallus growth and gametangia development, and that these effects may depend on this second-messenger level. Elevated cAMP stimulated thallus growth and delayed gametangia development; decreased cAMP inhibited thallus growth and accelerated maturation of both antheridia and oogonia. These results suggest that the cAMP pathway participates in regulation of developmental processes in Chara vulgaris and that thallus growth and gametangia development require different cAMP levels in cells.
Morphological description of seeds is a required step for analysis of biodiversity in natural populations and may give clues to adaptive strategies in species evolution. A cardioid is the curve described by a point of one circumference rolling around another circumference of equal radius. Models based on adjustment of seed shape with cardioid curves have been described for Arabidopsis thaliana and the model legumes Lotus japonicus and Medicago truncatula. In this work the model is applied to analyze seed morphology in populations of two subspecies of Capparis spinosa growing in Tunisia. Adjustment of seed images to cardioid curves, followed by statistical analysis of similarity in the complete images as well as in each of four quadrants, allows an accurate description of seed shape. The results show differences in morphology between subspecies. Seeds of subsp. rupestris present higher diversity of shape than seeds of subsp. spinosa. This may indicate primitiveness of C. subsp. rupestris seeds, associated with nonspecialization. The results are discussed in relation to the ecological strategies of both subspecies in their evolution.
We studied the thermophilous grass Bromus erectus in Central Europe to determine its pattern of population genetic structure and genetic diversity, using ISSR-PCR fingerprinting to analyze 200 individuals from 37 populations. We found three genetic groups with a clear geographic structure, based on a Bayesian approach. The first group occurred west and south of the Alps, the second east and north of the Alps, and the third was formed by four genetically depauperated populations in Germany. The populations from Germany formed a subset of the Bohemian-Moravian populations, with one private allele. Two differentiation centers, one in the Atlantic- Mediterranean and the second in the Pannonian-Balkan area, were recognized by species distribution modeling. The geographic distribution of the genetic groups coincides with the syntaxonomic split of the Festuco-Brometea class into the Festucetalia valesiaceae and Brometalia erecti orders. We found a statistically significant decrease in mean ISSR bands per individual from south to north, and to a lesser extent from the east to west. The former was explained by Holocene long-distance migrations from southern refugia, the latter by the difference in the gradient of anthropopression. We hypothesize a cryptic northern shelter of the species in Central Europe in the putative Moravian-Bohemian refugium.
An efficient system for plant regeneration of Senna occidentalis from hypocotyl-derived callus was developed. Callus was induced from leaf and hypocotyl explants on MS medium amended with 9.04 μM 2,4-D + 2.22 μM BAP and 10.74 μM NAA + 2.22 μM BAP. Medium browning due to leaching of compounds from callus was encountered and ameliorated through incorporation of 2.84 μM ascorbic acid. Leaf-derived callus showed no shoot induction ability, while hypocotyl-derived callus produced shoots in all cytokinin-amended treatments and also in combination with 2.68 μM NAA. For shoot formation, BAP-augmented treatments were better than medium with Kin added. Rhizogenesis was better on 1/2 MS basal medium with IBA than in the NAA and IAA treatments. Regenerated plants were acclimatized with 94% survival and showed similar morphology to field-grown plants.
The study examined tyrosol glucosyltransferase activity and the efficiency of salidroside production in natural and transformed root cultures of Rhodiola kirilowii (Regel) Regel et Maximowicz. Neither enzyme activity nor salidroside accumulation were detected in natural and transformed root cultures maintained in media without tyrosol. To induce TGase activity in biotransformation reactions, tyrosol was added to natural and transformed root cultures on the day of inoculation. The first peak of TGase activity (0.23 U/μg) was detected on day 9 in natural root culture, accompanied by the highest salidroside content (15.79 mg/g d.w.), but TGase activity was highest (0.27 U/μg) on day 15. In transformed root culture, day 18 showed the highest TGase activity (0.15 U/μg), which coincided with the highest salidroside content (2.4 mg/g d.w.). Based on these results, tyrosol was added to the medium on the days of highest previously detected activity of TGase: day 15 for natural root cultures and day 18 for transformed root cultures. This strategy gave significantly higher yields of salidroside than in the cultures supplemented with tyrosol on the day of inoculation. In natural root culture, salidroside production reached 21.89 mg/g d.w., while precursor feeding in transformed root cultures caused a significant increase in salidroside accumulation to 7.55 mg/g d.w. In all treatments, salidroside production was lower in transformed than in natural root cultures.
In flowering plants, seeds are produced both sexually (double fertilization is required) and asexually via apomixis (meiotic reduction and egg fertilization are omitted). An apomictic-like pattern of endosperm development in planta is followed by fis mutants of sexual Arabidopsis thaliana. In our experiments in planta, autonomous endosperm (AE) developed in met1 mutants. Furthermore we obtained autonomous endosperm formation in vitro not only in unfertilized ovules of fie mutants but also in wild genotypes (Col-0, MET1/MET1, FIE/FIE) and met1 mutants. AE induction and development occurred in all genotypes on the each of the media used and in every trial. The frequency of AE was relatively high (51.2% ovaries) and genotype-dependent. AE induced in vitro represents a more advanced stage of development than AE induced in fie mutants in planta. This was manifested by a high number of nuclei surrounded by cytoplasm and organized in nuclear cytoplasmic domains (NCDs), nodule formation, division into characteristic regions, and cellularization. The high frequency of AE observed in homozygous met1 (met1/met1) mutants probably is due to accumulation of hypomethylation as an effect of the met1 mutation and the in vitro conditions. AE development was most advanced in FIE/fie mutants. We suggest that changes in the methylation of one or several genes in the DNA of Arabidopsis genotypes caused by in vitro conditions resulted in AE induction and/or further AE development.
Self-incompatibility (SI) is a genetic system that promotes outcrossing by rejecting self-pollen. In the Brassicaceae the SI response is mediated by the pistil S-locus receptor kinase (SRK) and its ligand, pollen Slocus cysteine-rich (SCR) protein. Transfer of SRK-SCR gene pairs to self-fertile Arabidopsis thaliana enabled establishment of robust SI, making this transgenic self-incompatible A. thaliana an excellent platform for SI analysis. Here we report isolation of a novel A. thaliana self-incompatibility mutant, AtC24 SI mutant, induced by heavy-ion beam irradiation. We show that the AtC24 SI mutant exhibits breakdown of SI, with pollen hydration, pollen tube growth and seed set resembling the corresponding processes in wild-type (self-fertile) A. thaliana. Further reciprocal crosses indicated that some perturbed SI factor in the stigmatic cell of the AtC24 SI mutant is responsible for the observed phenotype, while the pollen response remained intact. Our results demonstrate successful application of heavy-ion beam irradiation to induce a novel A. thaliana self-incompatibility mutant useful for SI studies.
Somatic chromosome numbers are given for the following Taraxacum species: T. pieninicum, 2n=16; T. dentatum, 2n=24; T. fascinans, 2n=24; T. mendax, 2n=40; T. subalpinum, 2n=24; T. telmatophilum, 2n=24; T. cyanolepis, 2n=24; T. fulgidum, 2n=24; T. gentile, 2n=24; and T. undulatum, 2n=24. Chromosome numbers from Poland are published for the first time for T. dentatum, T. fascinans, T. mendax, T. subalpinum, T. telmatophilum, T. cyanolepis, T. fulgidum, T. gentile and T. undulatum.
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