1,721,013 research outputs found
Differential staining for cellulosic and modified plant cell walls
No full textA simple method to enhance the staining of cell wall components for fluorescence microscopy is described. In stems of Nicotiana tabacum and needles of Pinus eldarica lignin, the cuticle and unsaturated lipids are indicated by a purple-red fluorescence while pectocellulosic components fluorescc pale blue
The in-vitro response of pollen germination and tube length to different types of acidity
No full textPollen germination and tube growth are among the most sensitive responses to atmospheric pollution. Both these are inhibited by the acidity of the growth medium. Pollen grains from two species (Pinus cembra L. and Sambucus nigra L.) were germinated in media over a range of pHs (5·0, 4·5, 4·0, 3·5, 3·0 and 2·5) and six types of acidity (H2SO4, HNO3, H2SO4: HNO3 in 1:1, 2:1, 3:1 and 5:1 ratio). Pollen of the Gymnosperm is shown to be more resistant to acidity in the medium. Sulphuric acid alone and the ratio 2:1 with nitric acid are demonstrated to be the more harmful for P. cembra and S. nigra, respectively. The latter species was sensitive to all mixtures, particularly in respect to germination percentage
Cytoplasmic differences between the pollen grains of two cultivars of Malus domestica borkh. correlated with viability and germination
No full textThe ultramicroscopic study of pollen grains from two cultivars of Malus domestica, Starkrimson and Golden Delicious, revealed well-developed mitochondria and conspicuous endoplasmic reticulum in the first variety, suggesting greater metabolic activity. Incorporation of tritiated thymidine and uridine in the hydrated grains of both cultivars indicated replication of DNA and transcription within both mitochondria and plastids
Protein Characterization of Protein Bodies from Cotyledons of Mucuna pruriens (L.) DC
No full textSeeds of Mucuna pruriens (L.) DC. (Fabaceae) were analyzed for protein composition of protein bodies isolated from cotyledons. Protein bodies were successfully separated by Lympholyte and those of dry seeds, observed by scanning electron microscope, were elliptical or spherical in shape with a diameter of 5-12 μm. Protein content in dry seed protein bodies was 10.6 mg/g dry weight. Globulin was the largest protein fraction isolated (62.5 %), followed by albumin (18.3 %), glutelin (15.8 %) and prolamin (3.4 %). The prolamin fraction and high glutelin content are uncommon in legumes. SDS-PAGE of albumins, globulins, prolamins and glutelins provided different band numbers and molecular weights under reducing and non reducing conditions and suggested that the albumin fraction is rich in disulphide bonds. © 2013 Springer Science+Business Media New York
Differences in the activity and distribution of peroxidase from three different portions of germinative Brassica oleracea seeds.
Full text linkPeroxidase (POD, EC 1.11.1.7) activity, cellular localization and isozyme patterns were investigated in the seed integument, cotyledon and embryo axis of Brassica oleracea cv. Cappuccio during pregermination and seedling growth. Seeds started to germinate after 24 h of imbibition. POD activity was localized in the pigmented layer of the integument and in procambial strands of the cotyledon and embryo axis in the first 24 h of imbibition. It was localized in the integumental cells of palisade, pigmented and aleurone layers and in epidermal, meristematic, procambial cells and xylem elements of the root and hypocotyl after 48 h of imbibition. POD activity increased during germination and early seedling growth: in the integument, it reached a maximum value after 72 h of imbibition, in the embryo axis and cotyledons, it increased up to 144 h of imbibition. The increase in peroxidase activity was accompanied by the appearance of new isozymes correlated with the development of seedling tissues. The isozyme profile was characterized by nine peroxidases: isoperoxidase of 50 kDa peculiar to integuments, that of 150 kDa to cotyledons and that of 82 kDa to the embryo axis. During pregerminative phase isozymes of 84 kDa were detected in the integument and cotyledons, of 48.5 kDa in the embryo axis. After germination, peroxidase activity and the complexity of the isozyme pattern increased, suggesting that they play a relevant role after rupture of the integument
Brassica seed coat peroxidase [Perossidasi nel tegumento del seme di Brassica]
No full textPeroxidase activity was tested in Brassica oleracea seed integument during germination. POD activity increases from 24 to 72 h after seed imbibition with no significative changes from 72 to 144 h. Maximum level of enzyme activity was reached 48 h after the radicle protrusion. After germination the enzyme has been localized in the cell walls of palizade, pigmented and aleurone layers and in the cytoplasm of aleurone cells
Strategic compromise, policy bundling and interest group power: Theory and evidence on education policy
No full textPolicy reforms are often multifaceted. In the rent-seeking literature policies are usually taken as one-dimensional. This paper models policy formation using a political contest with endogenous policy proposals containing two dimensions, e.g. access and quality of education. The two dimensions provide an opportunity to trade off one policy over another to make the lobbying opposition less aggressive. In a first stage, the government proposes a reform over the two policies, and in a second stage engages in a contest with an interest group over the enactment of the proposed reform. As a result, the government makes a compromise, under-proposing in the policy the interest group opposes and over-proposing in the policy the interest group desires. Effectively, there will be strategic bundling of desired policies with undesired ones in an attempt to increase enactment probability and overall utility. We study this prediction empirically using a newly complied dataset on education legislation in the states of California, Illinois and Texas. Results suggest that stronger opposition is associated with less quality reforms. Moreover, as predicted by the model, when bundling access reforms together with quality, the negative effect is counteracted
Characterization of additives in plastics: from MS to MS10 multistep mass analysis and theoretical calculations of tris(2,4-di-tert-butylphenyl)phosphate
No full textIn the analysis by electrospray (+) of an extract of hemp sprouts put in a polypropylene vial, we found a large contamination of a plastic additive. It was characterized by multiple-stage MSn experiments (MS ÷ MS10) and identified as tris(2,4-di-tert-butylphenyl)phosphate, also known with the synonyms F32IRS6B46, oxidized Naugard 524, and others. The MS2 ÷ MS7 spectra are characterized by consecutive eliminations of six isobutene molecules from the tert-butyl moieties, some of them also occurring in the ion source. The first three are calculated to occur preferentially from the ortho positions, whereas eliminations from the para positions are estimated to be less favored at about 5–6 kcal/mol in each step. Once the first three isobutene molecules are eliminated, the remaining three are lost from the tert-butyl moieties in para positions (MS5 ÷ MS7), yielding protonated triphenylphosphate, whose structure has been confirmed by the MS2 spectrum of triphenylphosphate standard: the latter spectrum is almost superimposable with the MS8 spectrum of the analyte under investigation. MS8 and MS9 spectra show main losses of water and C6H4 molecules. The MS10 spectrum of precursor ions at m/z 215 shows the gas-phase addition of water and methanol and ions at m/z 168, attributable to the loss of a phosphorus oxide radical. Density functional theory (DFT) calculations (Becke 3LYP [B3LYP] 6-311+G(2d,2p)) have been used to evaluate structure and stability of different ionic and neutral species involved in the decomposition pathways and to calculate thermochemical data of the decomposition reactions. This multistep mass analysis combined with theoretical calculations resulted to be particularly useful and effective, yielding chemical, thermochemical, and mechanistic data of significant utility in the structural characterization and identification of the unknown analyte as well as to define its gas-phase reactivity under a multistep low-energy collision-induced dissociation regime
Antheridial dehiscence in ferns
No full textWe investigated the mechanism of antheridial dehiscence in ferns for the first time using fluorescence microscopy as well as scanning and transmission electron microscopy. The mechanism leading to antheridial dehiscence in Polystichum setiferum, Asplenium trichomanes and A. onopteris was found to depend on the different cellulose contents of the inner and outer walls of the ring cells detected with calcofluor white stain and the Thie ́ry test. The extremely low cellulose content of the ring cell walls facing spermatozoids made them less mechanically resilient than external wall cells. When the ring cells absorbed water they expanded only into the antheridial cavity, pushing the gametes against the cap cell, which detached from the ring cell below and enabled spermatozoid release. The newly released spermatozoids were spherical bodies covered in cellulose fibrils. The significance of cellulose fibrils could be to isolate the gametes from each other, to reinforce the electron transparent material and to protect the gamete from pressure created by the ring cells during release
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