Elevated [CO2], temperature increase and N supply effects on the turnover of below-ground carbon in a temperate grassland ecosystem

The effects of elevated [CO₂] (700 μl l^-1 CO₂) and temperature increase (+3 °C) on carbon turnover in grassland soils were studied during 2.5 years at two N fertiliser supplies (160 and 530 kg N ha^-1 y^-1) in an experiment with well-established ryegrass swards (Lolium perenne) supplied with the same amounts of irrigation water. During the growing season, swards from the control climate (350 μl l^-1 [CO₂] at outdoor air temperature) were pulse labelled by the addition of ¹³CO₂. The elevated [CO₂] treatments were continuously labelled by the addition of fossil-fuel derived CO₂ (^{13 C} of -40 to -50 ‰). Prior to the start of the experimental treatments, the carbon accumulated in the plant parts and in the soil macro-organic matter (‘old’ C) was at −32‰. During the experiment, the carbon fixed in the plant material (‘new’ C) was at −14 and −54‰ in the ambient and elevated [CO₂] treatments, respectively. During the experiment, the ¹³C isotopic mass balance method was used to calculate, for the top soil (0–15 cm), the carbon turnover in the stubble and roots and in the soil macro-organic matter above 200 μ (MOM). Elevated [CO₂] stimulated the turnover of organic carbon in the roots and stubble and in the MOM at N+, but not at N−. At the high N supply, the mean replacement time of ‘old’ C by ‘new’ C declined in elevated, compared to ambient [CO₂], from 18 to 7 months for the roots and stubble and from 25 to 17 months for the MOM. This resulted from increased rates of ‘new’ C accumulation and of ‘old’ C decay. By contrast, at the low N supply, despite an increase in the rate of accumulation of ‘new’ C, the soil C pools did not turnover faster in elevated [CO₂], as the rate of ‘old’ C decomposition was reduced. A 3 °C temperature increase in elevated [CO₂] decreased the input of fresh C to the roots and stubble and enhanced significantly the exponential rate for the ‘old’ C decomposition in the roots and stubble. An increased fertiliser N supply reduced the carbon turnover in the roots and stubble and in the MOM, in ambient but not in elevated [CO₂]. The respective roles for carbon turnover in the coarse soil OM fractions, of the C:N ratio of the litter, of the inorganic N availability and of a possible priming effect between C-substrates are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

A study on the environmental aspects of WEEE plastic recycling in a Brazilian company

Purpose

The high consumption of electrical and electronic equipment motivated by the rapid technological advances seen over the years has lead to an increase in the generation of waste electrical and electronic equipment (WEEE). Such residues contain various dangerous substances and therefore deserve special attention. To that end, the Brazilian Policy on Solid Waste has provided guidelines on integrated and solid waste management, such as consumer electronics, aiming at their appropriate disposal and treatment through reverse logistics. In this context, the present work focuses on studying the recycling of some WEEE plastics.

Methods

This study was conducted using the methodological framework presented in the International Standard ISO 14040:2006 and aimed to determine the life cycle inventory (LCI) of a WEEE plastic recycling process in a company in Brazil. Having collected the data, it was possible to identify and quantify the environmental aspects caused by the recycling process of major plastics (acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS). The study was conducted in the only company in Brazil that operates WEEE plastic recycling in large scale.

Results and discussion

Some of the environmental aspects caused during the recycling process of the plastics under study were identified and quantified. As a result, besides presenting the inventory, it was also possible to determine a reduction in the consumption of energy and in CO₂ emissions. When compared to the production of virgin ABS and HIPS, the recycling processes for such plastics showed a reduction in energy consumption by approximately 90% for both plastics and a reduction in CO₂ emissions by approximately 84% for HIPS and 87% for ABS. The plastics recycled by the company retain over 90% of their virgin mechanical properties.

Conclusions

The study shows that recycling is highly relevant and that components present in WEEE received appropriate destination and treatment. Recycling avoids environmental impacts as it prevents WEEE from being disposed of in landfills and as the pellets of recycled plastics can re-enter the supply chain as raw materials. Considering the legislation in Brazil, the stage of collection/transport/treatment of WEEE conducted by the company under study presents strong indications of contributions to the environment, society, and economy of the country.

     

Along the trail from Fraction I protein to Rubisco (ribulose bisphosphate carboxylase-oxygenase)

This historical minireview deals with events leading to the eventual discovery of Rubisco (ribulose bisphosphate carboxylase-oxygenase). This abundant leaf protein is not only responsible for the net fixation of CO₂ in all plants, but also causes the loss of carbon through photorespiration. The latter is a special ‘problem’ of the so-called ‘C₃’ plants. The protein was first called ‘Fraction 1 protein’ before it was recognized to be the same as Rubisco. Instead of reinventing words, text as needed has been freely used from three earlier publications (Wildman and Kwanyuen 1978; Wildman 1992, 1998) This revised version was published online in June 2006 with corrections to the Cover Date.     

Microbial population,fungal biomass and CO2 evolution in maize (Zea mays L.) field soils

Summary CO₂ evolution, fungal biomass and microbial population of two maize field soils differing in agricultural systemsviz., permanent agriculture on plain lands in valleys and ‘slash and burn’ type of shifting agriculture, were estimated at monthly intervals for one crop cycle. The results showed significant positive correlation among CO₂ evolution, fungal biomass, microbial population, organic C and total N. There was significant positive correlation between bacterial population and moisture content in both the agricultural systems. Microbial population and CO₂ evolution were always higher in the soils of permanent agriculture as compared to that of ‘slash and burn’ type of shifting agriculture.     

Differences in abscisic acid concentration in roots and leaves of two young Olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.) cultivars in response to water deficit

Differences in abscisic acid (ABA) accumulation between two olive cultivars were studied by enzyme-linked immunosorbent assay in roots and leaves, leaf water potential (Ψ_l), stomatal conductance (g _s) as well as photosynthetic rate (A) were also determined in well-watered (WW) and water-stressed (WS) plants of two olive cultivars ‘Chemlali’ and ‘Chetoui’. ‘Chemlali’ was able to maintain higher leaf CO₂ assimilation rate and leaf stomatal conductance throughout the drought cycle when compared with ‘Chetoui’. Furthermore, leaf water potential of ‘Chemlali’ decreased in lower extent than in Chetoui in response to water deficit. Interestingly, significant differences in water-stress-induced ABA accumulation were observed between the two olive cultivars and reflect the degree of stress experienced. Chemlali, a drought tolerant cultivar, accumulated lower levels of ABA in their leaves to regulate stomatal control in response to water stress compared to the drought sensitive olive cultivar ‘Chetoui’ which accumulated ABA in large amount.     

Photoautotrophic shoot and root development for triploid melon

The aim of this investigation was to establish environmental factors which promote growth and photosynthesis of melon (Cucumis melo L.) shoot buds, in vitro, and determine if photoautotrophic shoots had superior root forming ability in photoautotrophic environments. Buds from the triploid melon clone ‘(L-14×B)×L-14’ were observed for 21 days after transfer from a multiplication MS medium with 3% sucrose and 10 μM benzyladenine (BA) to a shoot development medium with 1 μM BA at three levels of sucrose in the medium (0, 1 and 3%), and light (50, 100 and 150 PPF) and CO₂ (500, 1000 and 1500 ppm) in the culture chamber. More shoot buds were observed with 3% sucrose in the medium. Increased light and CO₂ had a positive interaction with shoot proliferation. Fresh and dry weights were greatest at 3% sucrose, 150 PPF light and 1500 ppm CO₂. Shoot buds grew more slowly in sugar-free medium, but fresh and dry weight still doubled over 21 days of culture. Net photosynthetic rates (NPR) of buds were negative after four days in treatment conditions, but became positive after transfer to fresh, sugar-free medium. Two triploid genotypes of melon were (1) grown in vitro with sugar (photomixotrophic) and without sugar (photoautotrophic), (2) rooted in sugar-free media, both in a laboratory controlled environment chamber (in vitro) and a greenhouse acclimatization unit (ex vitro), and (3) compared for subsequent nursery growth in the greenhouse unit. The genotype ‘(L-14×B)×L-14’ produced more shoots than ‘(L-14×B)×Mainstream’ in both photomixotrophic or photoautotrophic conditions. ‘(L-14×B)×L-14’ rooted as well from either photoautotrophic and photomixotrophic shoots but ‘(L-14×B)×Mainstream’ rooted less frequently from photoautotrophic shoots. Seventy-six percent of the shoots in the laboratory controlled environment chamber were able to root photoautotrophically, whereas 47% of the shoots in the greenhouse acclimatization unit were rooted. Between 77% and 88% of plantlets from all treatment combinations survived transfer to the nursery. After growth in the nursery, the sizes of plants (fresh weight, dry weight, leaf area) were the same for either genotype, from either photoautotrophic or photomixotrophic shoots. Nursery plants that had been rooted in the laboratory controlled environment chamber were larger than those rooted in the acclimatization greenhouse chamber. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determination of self-locompatibility genotypes of Korean apple cultivars based on S-RNase PCR

To prevent self-fertilization, apple has a gametophytic self-incompatibility mechanism, part of a widespread intraspecific system, that is controlled by a multi-allelic locus. This attribute has been exploited in breeding programs for new cultivars. Likewise, many apple orchards depend on artificial pollination. Therefore, molecular analysis and early identification of the self-incompatibility (S) genotype could greatly improve breeding schemes and pollen donors selection. Here, we PCR-amplified the S-RNase PCR fragments from a total of 14 cultivars and parents, using new primers (ASPF3+ASPR3) common to 23 S-alleles in apple. The S-genotypes were determined for the following: ‘Hongro’ (S₁S₃), ‘Gamhong’ (S₁S₉), ‘Saenara’ (S₁S₃), ‘Chukwang’ (S₃S₉), ‘Hwahong’ (S₃S₉), ‘Seokwang’ (S₃S₃), ‘Hwarang’ (S₁S₉), ‘Sunhong’ (S₃S₉), ‘S.E.B.’ (S₁S₁₉), ‘S.G.D.’ (S₂S₃), and ‘Mollie’s Delicious’ (S₃S₇). We also confirmed the characteristics of the S-genotypes for eight Korean apple cultivars by PCR-Southern blot analysis, using seven S-RNases as probes.     

Expression of ethylene response genes during persimmon fruit astringency removal

Thirteen ethylene signaling related genes were isolated and studied during ripening of non-astringent ‘Yangfeng’ and astringent ‘Mopan’ persimmon fruit. Some of these genes were characterized as ethylene responsive. Treatments, including ethylene and CO₂, had different effects on persimmon ripening, but overlapping roles in astringency removal, such as increasing the reduction in levels of soluble tannins. DkERS1, DkETR2, and DkERF8, may participate in persimmon fruit ripening and softening. The expression patterns of DkETR2, DkERF4, and DkERF5 had significant correlations with decreases in soluble tannins in ‘Mopan’ persimmon fruit, suggesting that these genes might be key components in persimmon fruit astringency removal and be the linkage between different treatments, while DkERF1 and DkERF6 may be specifically involved in CO₂ induced astringency removal. The possible roles of ethylene signaling genes in persimmon fruit astringency removal are discussed.     

Growth and net photosynthetic rates of <Emphasis Type="Italic">Hosta</Emphasis> ‘blue vision’ during acclimatization in bright,natural light with CO<Subscript>2</Subscript> enrichment

Summary Hosta ‘Blue Vision’, a shade-adapted perennial, was successfully acclimatized in high, natural light conditions in the research Acclimatron^TM at Clemson University, Clemson, SC during the summer of 2000. The supplemental CO₂ levels achieved during acclimatization were 710±113, 2396±121, and 5641±119 μmol mol⁻¹, approximately 2×, 6×, and 15× ambient CO₂. Plants were maintained in H₂O-saturated atmospheres and protected from temperature increases associated with high light intensity. In the 5 wk following ex vitro transfer, plantlet roots grew at the 2× CO₂ level, but shoot biomass was unaffected. Results for the 6× and 15× CO₂ levels were comparable and provided the best plantlet growth. The “doubling time’ that is characteristic of exponential growth was 10.8 and 9.8 d for root and shoot dry weights, respectively. There was no indication of light saturation of net photosynthetic rate (NPR) over the photosynthetic photon flux density (PPFD) range of 100–1200 μmolm⁻²s⁻¹ experienced during this study. An interaction between CO₂ and light intensity levels was detected for NPR of Hosta ‘Blue Vision’ with CO₂ saturation occurring at approximately 2800 μmol mol⁻¹. regardless of light level. Furthermore, at the optimal CO₂ level, NPR increased quadratically as light intensity increased, and NPR was greatest at the maximum light intensity (PPFD: 1200 μmol m⁻²s⁻¹).     

Influence of Phosphorus on Gas Exchange and Plant Growth of Two Morphologically Distinct Types of Capsicum Annuum

Tolerance to phosphorus stress was studied in Capsicum annuum L. Chile ancho cv. San Luis and bell pepper cv. Jupiter plants. Plants were fertilized weekly with Long-Ashton nutrient solution (LANS) modified to supply 0, 11, 22, 44, 66, or 88 g(P) m^-3 (P0, P11, P22, P44, P66, P88). Phosphorus stress occurred in both cultivars at P0 and P11, with reduced plant growth and development. At P0, the lowest percentage of total biomass was directed toward reproductive growth. The root/shoot ratio was greatest at P0, reflecting greater dry matter partitioning to the root system. Growth of ‘San Luis’ was more sensitive to phosphorus stress than ‘Jupiter’. A greater percentage of total biomass was directed towards reproductive growth in ‘Jupiter’ than ‘San Luis’. Increasing P nutrition elevated leaf tissue P in both cultivars with highest leaf tissue P at P88. There were no differences in tissue P between P0 and P11 ‘San Luis’ plants, whereas P0 ‘Jupiter’ plants had the lowest tissue P. Low P-plants generally had the highest tissue N and lowest S, Mn, and B. In both cultivars, gas exchange was lowest at P0, as indicated by reduced stomatal conductance (g_s) and net photosynthetic rate (P_N). Internal CO₂ concentration and leaf-to-air vapor pressure difference (VPD) were generally highest with P-stressed plants. Phosphorus use efficiency, as indicated by P_N per unit of leaf tissue P concentration (P_N/P), was highest at P11. Generally, no P treatments exceeded the gas exchange levels obtained by P44 (full strength LANS) plants. Both P_N and g_s declined during reproductive growth in ‘San Luis’, which fruits more rapidly than ‘Jupiter’, whereas no reduction in gas exchange occurred with ‘Jupiter’. This revised version was published online in September 2006 with corrections to the Cover Date.     

Galactose metabolism in cell walls of opening and senescing petunia petals

Galactose was the major non-cellulosic neutral sugar present in the cell walls of ‘Mitchell’ petunia (Petunia axillaris × P. axillaris × P. hybrida) flower petals. Over the 24 h period associated with flower opening, there was a doubling of the galactose content of polymers strongly associated with cellulose and insoluble in strong alkali (‘residual’ fraction). By two days after flower opening, the galactose content of both the residual fraction and a Na₂CO₃-soluble pectin-rich cell wall fraction had sharply decreased, and continued to decline as flowers began to wilt. In contrast, amounts of other neutral sugars showed little change over this time, and depolymerisation of pectins and hemicelluloses was barely detectable throughout petal development. Size exclusion chromatography of Na₂CO₃-soluble pectins showed that there was a loss of neutral sugar relative to uronic acid content, consistent with a substantial loss of galactose from rhamnogalacturonan-I-type pectin. β-Galactosidase activity (EC 3.2.1.23) increased at bud opening, and remained high through to petal senescence. Two cDNAs encoding β-galactosidase were isolated from a mixed stage petal library. Both deduced proteins are β-galactosidases of Glycosyl Hydrolase Family 35, possessing lectin-like sugar-binding domains at their carboxyl terminus. PhBGAL1 was expressed at relatively high levels only during flower opening, while PhBGAL2 mRNA accumulation occurred at lower levels in mature and senescent petals. The data suggest that metabolism of cell wall-associated polymeric galactose is the major feature of both the opening and senescence of ‘Mitchell’ petunia flower petals.     

Influence of endogenous and exogenous RNases on the variation of pollen cytosolic-free Ca2+ in Pyrus serotina Rehd

The objective of this study was to examine whether S-RNase plays a specific role in the pre-germinated Pyrus pollen. Effects of exogenous RNase and endogenous S-RNase on concentration of cytosolic-free calcium ([Ca²⁺]_i) variation of pre-germinated Pyrus pollen were studied. [Ca²⁺]_i variation caused by different RNases were complex. In 1 h after being cultured, exogenous RNase, RNase T₁ and RNase A, and endogenous incompatible ‘Hohsui’ RNase promoted the [Ca²⁺]_i of ‘Hohsui’ pollen. Acid proteins of ‘Hohsui’ had no remarkable influence on the [Ca²⁺]_i of self-pollen. Endogenous compatible ‘Kohsui’ RNase reduced the [Ca²⁺]_i of ‘Hohsui’ pollen, but compatible ‘Hohsui’ RNase can stimulate the [Ca²⁺]_i of ‘Kohsui’ pollen. RNase T₁, RNase A and incompatible ‘Kohsui’ S-RNase can also make ‘Kohsui’ pollen [Ca²⁺]_i increase. Different from ‘Hohsui’ pollen, acid proteins of ‘Hohsui’ pull down the ‘Kohsui’ pollen [Ca²⁺]_i remarkably. Conclusion can be made that during the prophase of pollen germination, endogenous S-RNase has no specific effect on pollen [Ca²⁺]_i changes.     

Photoautotrophic culture conditions and photosynthetic photon flux influence growth of <Emphasis Type="Italic">Lilium</Emphasis> bulblets <Emphasis Type="Italic">in vitro</Emphasis>

Summary Lilium Asiatic hybrid ‘Mona’ bulblets were cultured in vitro for 100 d under photoautotrophic (CO₂-enriched conditions and without sucrose in the medium) and heterotrophic (non-enriched CO₂ conditions and sucrose-supplemented medium) methods and under various levels of photosynthetic photon flux (PPF). Bulblet growth and net photosynthetic rate (NPR) were analyzed. CO₂₋ and PPF-enriched conditions enhanced the overall growth of bulblets, scale leaves, and roots. Heterotrophic conditions enhanced bulblet growth but higher PPF levels were inhibitory to the development of scale leaves. These results indicate the CO₂₋ and PPF-enriched conditions (photoautotrophic conditions) are beneficial for the production of high-quality bulblets of Asiatic hybrid lilies in vitro     

Mobilization and exudation of photo-assimilated14C by developing pods of groundnut (Arachis hypogaea L.)

Summary ‘Pod washings’ were collected from groundnut at three hour intervals for 24 hours after feeding the plants with¹⁴CO₂. Low radioactivity was found in the first four ‘Pod washings’ of 10 day old pods and the radioactivity increased with time. Highest radioactivity was found in washings of 20 and 30 day old pods and was twice the activity found in the washings of 50 day old pods. The radioactivity of both ethanol-soluble and insoluble fractions in pods was determined. The radioactivity mobilized into the pods increased with age and it was highest in 50 day old pods. The influence of the pod exudates on geocarposphere microflora during pod development is discussed.     

Accumulation of additive effects generates a strong photoperiod sensitivity in the extremely late-heading rice cultivar ‘Nona Bokra’

Many rice cultivars that originated from lower-latitude regions exhibit a strong photoperiod sensitivity (PS) and show extremely late heading under long-day conditions. Under natural day-length conditions during the cropping season in Japan, the indica rice cultivar ‘Nona Bokra’ from India showed extremely late heading (202 days to heading) compared to the japonica cultivar ‘Koshihikari’ (105 days), from Japan. To elucidate the genetic factors associated with such extremely late heading, we performed quantitative trait locus (QTL) analyses of heading date using an F₂ population and seven advanced backcross progeny (one BC₁F₂ and six BC₂F₂) derived from a cross between ‘Nona Bokra’ and ‘Koshihikari’. The analyses revealed 12 QTLs on seven chromosomes. The ‘Nona Bokra’ alleles of all QTLs contributed to an increase in heading date. Digenic interactions were rarely observed between QTLs. Based on the genetic parameters of the QTLs, such as additive effects and percentage of phenotypic variance explained, these 12 QTLs are likely generate a large proportion of the phenotypic variation observed in the heading dates between ‘Nona Bokra’ and ‘Koshihikari’. Comparison of chromosomal locations between heading date QTLs detected in this study and QTLs previously identified in ‘Nipponbare’ × ‘Kasalath’ populations revealed that eight of the heading date QTLs were recognized nearby the Hd1, Hd2, Hd3a, Hd4, Hd5, Hd6, Hd9, and Hd13. These results suggest that the strong PS in ‘Nona Bokra’ was generated mainly by the accumulation of additive effects of particular alleles at previously identified QTLs.     

Delimitation of a QTL region controlling cold tolerance at booting stage of a cultivar, ‘Lijiangxintuanheigu’, in rice, <Emphasis Type="Italic">Oryza sativa</Emphasis> L.

Low temperature at the booting stage of rice causes male sterility resulting in severe yield loss. Cold tolerance has long been an important objective in rice breeding. We identified a quantitative trait locus (QTL) for cold tolerance on the long arm of chromosome 3 from the cold-tolerant breeding line ‘Ukei 840’ by using F₂ and BC₁F₂ populations from crosses between ‘Ukei 840’ and ‘Hitomebore’. The cold tolerance of ‘Ukei 840’ is derived from the Chinese cultivar ‘Lijiangxintuanheigu’. The effect of this QTL on cold tolerance was confirmed by developing ‘Hitomebore’ chromosome segment substitution lines having ‘Lijiangxintuanheigu’ alleles on chromosome 3. By producing recombinants in chromosome 3, the QTL region for cold tolerance was delimited to the region of about 1.2-Mb region between RM3719 and RM7000. All lines heterozygous for the QTL showed seed fertilities as low as that of ‘Hitomebore’, suggesting that the ‘Lijiangxintuanheigu’ allele for cold tolerance in the QTL region is recessive. Determination of a 1.2-Mb nucleotide sequence of ‘Ukei 840’ and comparison with the published genomic sequence of ‘Nipponbare’ showed 254 SNPs, of which 11 were in coding regions of genes, seven in five genes being non-synonymous. SNPs were detected in the 5-kb upstream regions of 89 genes, but no differences of gene expression levels were detected between alleles of these genes. Although further delimitation is required to identify the gene responsible for cold tolerance of ‘Lijiangxintuanheigu’, SNP markers developed here will be useful for marker-assisted selection in a breeding program using ‘Lijiangxintuanheigu’ as a donor of cold tolerance.     

Evolution of early determinate tomato cultivars during the last three decades as a result of research conducted at Warsaw Agricultural University

Earliness is a crucial factor of tomato field production in Poland. A. Michalska and B. Kubicki (1978) conducted the first investigations on tomato earliness at the Department of Plant Genetics and Breeding. The main conclusions from these studies indicated that it was possible to obtain varieties earlier than ‘New Yorker’ as a result of transgression. The two new varieties (‘Alfa’ and ‘Akord F₁’) proved to be two weeks earlier than ‘New Yorker’. However, earliness was correlated with smaller fruit weight (30–40 g). At the next stage of experiment some improvement was achieved both in the size of fruit (45 g for ‘Beta’ up to 70 g for ‘Alka’) as well as colour intensity and good flavour. With the next few years fruit weight was still increased (up to 100 g for ‘Maskarena’) and a higher level of firmness was obtained (mid firm fruits for ‘Maskarena’ and ‘Delta’). At present, the Polish Research Centre for Cultivar Testing recommends our varieties ‘Betalux’, ‘Promyk’ and ‘Delta’ as standards.