Rhizodeposition of C and N in peas and oats after C-N double labelling under field conditions

Compounds released by plant roots during growth can make up a high proportion of below-ground plant (BGP) carbon and nitrogen, and therefore influence soil organic matter turnover and plant nutrient availability by stimulating the soil microorganisms. The present study was conducted to examine the amount and fate of C (CdfR) and N rhizodeposits (NdfR), in this study defined as root-derived C or N present in the soil after removal of roots and root fragments, released during reproductive growth. BGP biomass of peas (Pisum sativum L.) and oats (Avena sativa L.) was successfully labelled in situ with a ¹³C-glucose-¹⁵N-urea mixture under field conditions using a stem feeding method. Pea plants were labelled at the beginning of flowering and harvested 36 and 52 days after labelling at pod filling (P_P) and maturity (P_M), respectively. Oat plants were labelled at grain filling and harvested 42 days after labelling at maturity (O_M). CdfR was 24.2% (P_P), 29.6% (P_M) and 30.8% (O_M) of total recovered plant C. NdfR was 32.1% (P_P), 36.4% (P_M) and 30.0% (O_M) of total plant N. Due to higher N assimilation, amounts of NdfR were four times higher in peas in comparison with oats. The results for NdfR in peas were higher than results from other studies. The C-to-N ratio of rhizodeposits was lower under peas (17.3) than under oats (41.9) at maturity. At maturity, microbial CdfR at 0-30 cm soil depth was 37% of the microbial biomass C in peas and 59% in oats. Microbial NdfR was 15% of microbial N in peas and 5% in oats. Furthermore, inorganic NdfR was 34% in peas and 9% in oats at 0-30 cm at maturity. These results show that rhizodeposits of peas provide a more easily available substrate to soil microorganisms, which are incorporated to a greater extent and turned over faster in comparison with oats. Beside the higher amounts of N released from pea roots, this process contributes to the higher N-availability for subsequent crops.     

A possible genetic source for chipping potatoes from 40 F storage

An interspecific hybrid ofS. phureja x USW1, a haploid of Katahdin, produced acceptable potato chips when processed directly from 40 F (4.5 C) storage during 3 years of testing. It was crossed with 11 interspecific hybrids. Tubers from these progenies were stored for 5 weeks at 40 F and then chipped immediately for 55 seconds in vegetable oil maintained at 375 F (190 C). Of 645 seedlings tested, chip color was acceptable in 17 and variable in 18. A group of 600 seedlings fromS. tuberosum parents treated comparably produced black-colored chips without exception.     

Der Baobab (Adansonia digitata L.): Wildobst aus Afrika für Deutschland und Europa?!

In Germany and Europe exotic fruits from distant places are becoming more and more important. In the tropics and subtropics an enormous variety of edible fruits exists. In 2008 the dry fruit pulp of the baobab (Adansonia digitata L.) was approved as novel food for the EU and thus entered the formal food market. Hence, an increasing number of products became available in Europe. The baobab is an impressive tree in the savannas of Africa. Due to its dense and wide spreading root system and its enormous water storing capacity in the stem, the tree can grow under very dry environmental conditions. In many regions of Africa it is a multipurpose indigenous fruit tree species which offers shelter and provides food, fodder and medicine as well as raw material for many purposes. However, even in Europe a wide range of products is now available as shown in the present study, which identified more than 300 baobab products or products with baobab as an ingredient. In Germany, not only the natural baobab pulp but also ready-made foodstuffs such as soft drinks, sandwich spreads, cereal bars, sweets and chocolates are available. Furthermore, a diverse range of pharmaceutical and cosmetic products with extracts from the baobab is available in the market. The products range from after shave and perfume to shampoo and shower gel to leg lotion and foot spray. In Germany baobab saplings and seeds are offered for planting and cultivation as an indoor pot plant. Commercially marketed baobab bonsai seedlings for the European market are produced in Senegal. In Africa the baobab fruits are mainly harvested from wild stands. However, the commercial production of baobab fruits in orchards could be an important future opportunity for income generation to many local households. More research on baobab, including the domestication of this wild fruit tree species, and the conservation of its natural stands as important genetic resource are prerequisites for sustainably increased fruit production.     

Detection of exotic QTLs controlling nitrogen stress tolerance among wild barley introgression lines

Nitrogen (N) is one of the most important plant nutrients, controlling growth and, ultimately, yield of a cultivar. Hordeum vulgare ssp. spontaneum, the wild barley progenitor of cultivated barley, is known to possess genes that can improve tolerance against biotic and abiotic stresses. A quantitative trait locus (QTL) study with two levels of N fertilization was conducted under glasshouse in order to locate wild barley alleles that improve N stress tolerance in the genetic background of an elite barley cultivar. For this, a set of 28 barley introgression lines (S42ILs), which originate from the cross ??Scarlett???×???ISR42-8??, was studied. The S42ILs, containing single or multiple wild barley introgressions, and ??Scarlett?? were evaluated in regard to a total of 15 traits, related to morphological parameters, grain parameters as well as to carbon (C) and N content parameters. A mixed model analysis and a subsequent Dunnett test was conducted to identify S42ILs that significantly deviate from the recurrent parent ??Scarlett??, either tested separately for each N level, or simultaneously across both N levels. In total, 65 QTLs were detected for the S42IL set. Most QTLs were found for chlorophyll content during heading (10 QTLs) and the fewest for C/N ratio of straw (1 QTL). The individual S42ILs possessed different numbers of QTLs. For S42IL-108, a maximum of eight QTLs were found whereas S42IL-145 did not show any significant difference from ??Scarlett??. Wild barley alleles revealed decreasing effects at 32 QTLs and increasing effects at 33 QTLs. Although 25 QTLs exhibited similar effects across both N levels, 18 and 22 QTLs exhibited effects that were only detected under N0 or N1, respectively. We, thus, conclude that it may be worth to select improved barley cultivars for N stress tolerance separately under low N fertilization, rather than extrapolating trait performances from experiments carried out under standard N fertilization conditions. A number of wild barley QTL alleles improved N stress tolerance. For example, a wild barley QTL allele on chromosome 4H, present in the Hsp introgression of S42IL-119, was associated with a 13.0?% increase of thousand grain weight across both N levels and a 20?% increase under low N supply. QTLs detected in the present study were compared with those of previous field studies of the same cross and with other QTL studies in barley and other small grains. Accordance between QTL studies (QTLs showing similar effects at the same map location) is documented and discussed. Based on our study, promising wild barley QTL alleles are available in S42ILs, which can be readily utilized to select for improved N use efficiency in barley breeding.     

Intestinal metabolism of two A-type procyanidins using the pig cecum model: detailed structure elucidation of unknown catabolites with Fourier transform mass spectrometry (FTMS)

Procyanidins, as important secondary plant metabolites in fruits, berries, and beverages such as cacao and tea, are supposed to have positive health impacts, although their bioavailability is yet not clear. One important aspect for bioavailability is intestinal metabolism. The investigation of the microbial catabolism of A-type procyanidins is of great importance due to their more complex structure in comparison to B-type procyanidins. A-type procyanidins exhibit an additional ether linkage between the flavan-3-ol monomers. In this study two A-type procyanidins, procyanidin A2 and cinnamtannin B1, were incubated in the pig cecum model to mimic the degradation caused by the microbiota. Both A-type procyanidins were degraded by the microbiota. Procyanidin A2 as a dimer was degraded by about 80% and cinnamtannin B1 as a trimer by about 40% within 8 h of incubation. Hydroxylated phenolic compounds were quantified as degradation products. In addition, two yet unknown catabolites were identified, and the structures were elucidated by Fourier transform mass spectrometry.     

Apigenin-induced suicidal erythrocyte death

Apigenin, a flavone in fruits and vegetables, stimulates apoptosis and thus counteracts cancerogenesis. Erythrocytes may similarly undergo suicidal cell death or eryptosis, characterized by cell shrinkage and phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+) activity ([Ca(2+)](i)), ceramide formation and ATP depletion. The present study explored the effect of apigenin on eryptosis. [Ca(2+)](i) was estimated from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine exposure from annexin V binding, hemolysis from hemoglobin release, ceramide utilizing antibodies, and cytosolic ATP with luciferin-luciferase. A 48 h exposure to apigenin significantly increased [Ca(2+)](i) (≥ 1 μM), increased ceramide formation (15 μM), decreased ATP concentration (15 μM), decreased forward scatter (≥ 1 μM), and increased annexin V binding (≥ 5 μM) but did not significantly modify hemolysis. The effect of 15 μM apigenin on annexin V binding was blunted by Ca(2+) removal. The present observations reveal novel effects of apigenin, i.e. stimulation of Ca(2+) entry, ceramide formation and ATP depletion in erythrocytes with subsequent triggering of suicidal erythrocyte death, paralleled by cell shrinkage and phosphatidylserine exposure.     

Smart spatial incentives for market-based conservation

Market-based instruments such as payments, auctions or tradable permits have been proposed as flexible and cost-effective instruments for biodiversity conservation on private lands. Trading the service of conservation requires one to define a metric that determines the extent to which a conserved site adds to the regional conservation objective. Yet, while markets for conservation are widely discussed and increasingly applied, little research has been conducted on explicitly accounting for spatial ecological processes in the trading. In this paper, we use a coupled ecological-economic simulation model to examine how spatial connectivity may be considered in the financial incentives created by a market-based conservation scheme. Land use decisions, driven by changing conservation costs and the conservation market, are simulated by an agent-based model of land users. On top of that, a metapopulation model evaluates the conservational success of the market. We find that optimal spatial incentives for agents correlate with species characteristics such as the dispersal distance, but they also depend on the spatio-temporal distribution of conservation costs. We conclude that a combined analysis of ecological and socio-economic conditions should be applied when designing market instruments to protect biodiversity.     

Remaining questions in the case for balanced harvesting

Balanced harvesting – harvesting all species and sizes in an ecosystem in proportion to their productivity – is a fisheries management strategy that has been suggested recently to increase yields, while reducing overall ecosystem impact. However, some aspects of balanced harvesting are controversial, including its call for extensive harvesting of juveniles and forage fish. Balanced harvesting also calls for targeting species and size‐classes that are not currently marketable, possibly at a significant economic cost. Some have argued that this cost is outweighed by the ecological benefits of maintaining the ecosystem size and trophic structures and by the benefits of extra yield for food security. There is broad consensus that balanced harvesting would require major changes to fishery management institutions and consumer behaviour, and it is unclear to what extent it is physically possible with current technologies. For this reason, we argue that steps to implement balanced harvesting are difficult to justify until the case for it is more clearly resolved. We outline some of the pivotal questions that must be answered to make a convincing case for or against balanced harvesting, many of which can be answered empirically. In identifying these questions, we hope to offer a constructive path forward in resolving some of the key issues in the balanced harvesting debate.