Bioaccumulation of Copper by Zea mays: Impact on Root, Shoot and Leaf Growth

In the present study, the growth and the Cu²⁺accumulation by roots, shoots and leaves of Zea mays were examined using copper sulphate in the range of 10^?4 to 10^?2 M. Plants of Z. mays did not show inhibition of growth in the presence of 10^?4 to 10^?2 M Cu²⁺; however, it was observed growth effects on root when different Cu²⁺ solution concentrations were used. Only the seedlings exposed to 10^?2 M exhibited substantial root growth reduction, yielding only 56% of length with respect to the control. Seedlings exposed to 10^?4 M Cu²⁺ exhibited 16% and 42% growth increase in shoots and leaves, respectively, when compared with the controls. The seedlings treated with 10^?3 and 10^?2 M Cu²⁺ were inhibited in shoot and leaf growth. The fresh weights in roots, shoots and leaves significantly decreased at 10^?2 M Cu²⁺. The tolerance index, based on root length, was not significantly different for the three different treatments with copper. However, the total accumulation rate was very low at 10^?4 and 10^?3 M compared to 10^?2 Cu treatments. The capacity of copper accumulation by roots, shoots and leaves of Z. mays plants increased concomitant to the copper concentration, arriving to 382 times more in roots, 157 in shoots and only 16 in leaves, all compared to the controls. Cu could be accumulated by roots, shoots and leaves when the initial concentrations were 10^?3 and 10^?4 M. However, when it was 10^?2 M, the metal could not be accumulated by leaf and shoot levels; the roots could increase their copper accumulation capacity three times compared to the control. Z. mays has potential ability to accumulate Cu without being overly sensitive to Cu toxicity.     

Evidence for a relationship between bovine erythrocyte lipid membrane peculiarities and immune pressure from ruminal ciliates

Erythrocytes of bovines and other ruminants have a strikingly anomalous phospholipid composition, with low or absent phosphatidylcholine (PC) together with high sphingomyelin (SM) content. Here, we report the presence in normal bovine serum of high levels of anti-phospholipid antibodies of IgM isotype against, PC and the phosphono analogue of phosphatidylethanolamine, aminoethylphosphonolipid (AEPL), normally produced by rumen ciliates. In contrast, no antibodies were detected against SM or N-acyl-phosphatidylethanolamine (NAPE), the major components of bovine erythrocytes. In addition, we found that exposure of the ciliate Tetrahymena thermophila to bovine serum results in rapid lysis, an effect that was inhibited by adsorption of the serum with SM/AEPL liposomes. Furthermore, incubation with bovine serum had a similar effect on freshly obtained ruminal ciliates, and the lytic activity was eliminated by pre-adsorption of the serum with SM/PE liposomes. The ruminant mode of life with its concomitant ciliate fauna is hereby linked to the peculiar conformation of bovine erythrocyte membranes. We propose that the unique phospholipid composition of bovine erythrocytes appears as an evolutionary adaptation to tolerate the lytic effects of anti-phospholipid antibodies generated against AEPL, a membrane component of the huge mass of ruminal ciliates, necessary commensals of this group of mammals.     

Carbon Sequestration in Restored Soils by Applying Organic Amendments

The study of different natural carbon sinks has become especially important because of climate change effects. The restoration of contaminated areas can be an ideal strategy for carbon sequestration. The studied area was affected by toxic Aznalcóllar mine spill in 1998. Restoration process of the contaminated area was based, mainly, on the use of two organic amendments: leonardite (LE) and biosolid compost (BC). The objective of this study was to verify whether the application of these amendments promotes the long‐term carbon sequestration in this soil. Five treatments were established: untreated control, biosolid compost (doses 4 and 2) and leonardite (doses 4 and 2). The addition of amendments implied an improvement in soil quality that was directly related to the amendment dose: decrease in bulk density, increase in pH, higher respiration rates and an improvement in the stratification ratio. Dose‐dependent changes in the molecular composition of soil organic matter were shown by nuclear magnetic resonance analysis. Both amendments promoted carbon retention, although because of the low mineralization rates of soil organic matter in LE treatments, the carbon storage was higher. The dosage effect on the carbon balance was more important in LE treatments, whereas in the BC treatments, the balance was similar for both doses. Our findings suggest that LE4 significantly increased the total organic carbon and it was the most suitable treatment for long‐term carbon storage, because of its molecular composition rich in relatively stable aromatic and lignin‐derived compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Use of culture-derived Fusarium oxysporum f. sp. cubense, race 1 filtrates for rapid and non-destructive in vitro differentiation between resistant and susceptible clones of field-grown banana

Banana and plantain are among the most important food crops in developing countries but production is threatened by increasing virulent forms of Fusarium oxysporum f. sp. cubense. Chemical control is not economically effective and,therefore, breeding programs are necessary. Traditional field studies of new genotype resistance to this disease are time-consuming and destructive. Therefore,we developed a rapid and non-destructive procedure to differentiate field-grown banana resistant from susceptible clones. This procedure implicates application of culture filtrates of Fusarium oxysporum f. sp. cubense race 1 onto banana leaves. The relationship between duration of the fungal in vitro incubation, and the fungal culture fresh mass, the culture filtrate absorbency, and the Gross Michel (susceptible cultivar)leaf lesion area (after application of the culture filtrate) were similar and at 24day-incubation the highest values of the recorded indicators were observed. A comparison between Gross Michel and FHIA-01(resistant) was also performed. The most relevant differences between cultivars were observed at 48 hours after application of the culture filtrate, and in the middle-aged leaves. The position of the culture filtrate application in the leaf limb (distal, middle, proximal) was not determinant. A wider comparison among banana cultivars confirmed previous results informed by other researchers using different systems to study this plant-fungus interaction. Such a confirmation validates the effectiveness of the procedure described here to select rapid and non-destructively banana resistance to this disease at field level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Potential of a Fusarium eumartii culture filtrate on the screening for wilting resistance in potato

Summary Fusarium solani f.sp. eumartii Carp. Snyder and Hansen (Fusarium eumartii) is a soil inhabitant that induces the so-called Potato Wilt and Stem End Rot disease. Prior to wilting, the pathogen induces peculiar small bronze spots on the leaflets. Failure to isolate F. eumartii from infected leaflets suggests the involvement of a toxin in the disease. The fungus was grown in liquid Richard's medium and thereafter a filtrate was obtained dialyzing (MW cutoff 12,000–14,000) and sterilizing the culture by filtration (0.22 m). Potato leaves treated with both the pathogen or the filtrate showed symptoms of bronze spots and significantly higher electrolyte leakage when compared to controls. Tomato leaves showed neither bronze spots nor electrolyte leakage after plant inoculation with the pathogen or with the filtrate treatment. Both, the absence of visible symptoms and the lack of electrolyte leakage in tomato could be associated to a certain degree of host specificity of the F. eumartii filtrate towards potato. The filtrate also induced symptoms similar to infections by F. eumartii in adult plants and in vitro plantlets of cultivars Huinkul MAG and Kennebec. Callus responses to the filtrate were related to responses of the cultivars to the pathogen in greenhouse. These results show the potential of the culture filtrate of F. eumartii for use in screening for wilting resistance.     

Cytogenetic variation in somatic tissue cultures and regenerated plants of barley (Hordeum vulgare L.)

Summary Chromosome number of morphogenic and non-morphogenic calli and regenerated plants of barley were determined. Cultures were obtained from two kinds of explants, immature embryos and seedling leaves from three cultivars, Ingrid, Dissa and Golden Promise. Callus chromosome analyses were carried out during a 12 month period in a medium containing 2 mg/l of 2,4-D. Diploid cells were predominant in all cases; although in leaf-derived cultures, retraploid cells (2n=4x=28) showed a tendency to increase as time in culture increased and after more than six months in culture, diploid cells decreased to percentages of almost 70%. Aneuploid cells were generally infrequent in all cases. The source of explant has been more important than the genotype (cultivar) and the type of callus (morphogenic vs. non-morphogenic) in the chromosomal stability of cultures as time increases. From short term cultures, only 1.85% of the regenerated plants were tetraploid, the remaining were diploids. The ability of morphogenic calli to regenerate plants decreased before any significant reduction of diploid cells were observed.     

High frequency somatic embryogenesis with a pampeana-derived genotype of alfalfa (Medicago sativa L.)

Summary Somatic embryos of genotype R11 of the alfalfa variety Pampeana were produced from embryogenic calli derived from leaf sections. They were induced by an auxin shock and its development was attempted on six different media. The best condition for somatic embryo production was inducing callus on MS medium plus 10 M 2,4-D and 4,6 M KIN and transferring them, after the auxin shock, to MS with 10–20 mM NH₄ ⁺ and 30 mM proline. More than 500 somatic embryos per plate were produced. Embryos were grown to plants on MS or half strength MS media and all regenerated plants resembled the original R11 genotype. This technique could be useful in alfalfa Pampeana improvement using genetic modification.     

A comparative physiologico-genetical study of activities of some enzymes in a heterotic single cross hybrid of maize (Zea mays L.)

Summary In field trials conducted over three growth seasons I studied the differences in activities of the enzymes: polyphenoloxidase, ascorbateoxidase and peroxidase, with a heterotic single-cross hybrid of maize and its pollen-sterile analogue. Additional observations were made for differences between the single-cross hybrids and their parental lines. The samples (staminate spikelets) were taken at random just before and after tasselling. Significant differences could be established concerning the object set. Comparison of the self-pollinating line of maize with the pollen-sterile analogue revealed the down ward trend in peroxidase (P) activity with the pollen-sterile line; the upward trend in polyphenoloxidase (PPO) activity and the downward trend in ascorbateoxidase (A) activity were observed with the pollen-sterile line before tasselling. After tasselling, activity of PPO showed a downward and that of A an upward trend. The single-crospollen-sterile hybrid revealed, compared to the parental lines, an upward trend in its PPO and A activities before tasselling and a downward trend in the same enzymes after tasselling; while activity of P in this single-cross, pollen-sterile hybrid indicated the downward trend in general. Compared with the parental forms, the pollen-fertile hybrid of maize showed a trend towards lower activities of the studied enzymes for all seasons and periods under observation. Comparing results in the single-cross hybrids there was an indication of higher activities of PPO and A in the pollen-sterile analogue; whereas the same analogue revealed a lower activity of P before tasselling and higher value after tasselling.