Apoplastic redox metabolism: Synergistic phenolic oxidation and a novel oxidative burst

The plant apoplast is an important mediator of communication between the cell cytoplasm and its surroundings. Plant cell suspensions offer a convenient model system to gain insight into apoplastic physiology. Here, we describe a novel phenomenon that took place when two naturally occurring phenolics were added together to either soybean or tobacco cell suspensions. Acetosyringone (AS) and/or hydroxyacetophenone (HAP), phenolics found in the extracellular/apoplast of tobacco cells, were added to soybean or tobacco cell suspensions undergoing an oxidative burst. Individually, AS appeared to be utilized as a typical peroxidase substrate to scavenge hydrogen peroxide, while HAP was utilized at a much lower rate. However, when added together the rate of utilization of both phenolics increased and surprisingly resulted in the production of hydrogen peroxide. We have further characterized this novel phenomenon in suspension cells. This study demonstrates that certain phenolics in plants can cause co-oxidation which, as in animals, could alter the structure and bioactivity of surrounding phenolics.     

Can additional N fertiliser ameliorate the elevated CO2‐induced depression in grain and tissue N concentrations of wheat on a high soil N background?

Elevated CO₂ stimulates crop yields but leads to lower tissue and grain nitrogen concentrations [N], raising concerns about grain quality in cereals. To test whether N fertiliser application above optimum growth requirements can alleviate the decline in tissue [N], wheat was grown in a Free Air CO₂ Enrichment facility in a low‐rainfall cropping system on high soil N. Crops were grown with and without addition of 50–60 kg N/ha in 12 growing environments created by supplemental irrigation and two sowing dates over 3 years. Elevated CO₂ increased yield and biomass (on average by 25%) and decreased biomass [N] (3%–9%) and grain [N] (5%). Nitrogen uptake was greater (20%) in crops grown under elevated CO₂. Additional N supply had no effect on yield and biomass, confirming high soil N. Small increases in [N] with N addition were insufficient to offset declines in grain [N] under elevated CO₂. Instead, N application increased the [N] in straw and decreased N harvest index. The results suggest that conventional addition of N does not mitigate grain [N] depression under elevated CO₂, and lend support to hypotheses that link decreases in crop [N] with biochemical limitations rather than N supply.     

Field Evaluation of Cocksfoot,Tall Fescue and Phalaris for Dry Marginal Environments of South‐Eastern Australia. 1. Establishment and Herbage Production

Newly developed candidate cultivars of cocksfoot (Dactylis glomerata L.), phalaris (Phalaris aquatica L.) and tall fescue (Festuca arundinacea Schreb. = syn. L. arundinaceum (Schreb) Darbysh.) were evaluated over four years for persistence and productivity against current commercial cultivars in small plots at five locations selected for lower and less reliable rainfall and difficult soils (low pH and high Al) in south‐eastern Australia known to be marginally too dry for these grass species. The five locations were ‐ representing summer dominant rainfall, Inverell, in northern New South Wales (NSW); ‐ representing uniform rainfall; Trungley Hall, (medium rainfall), and Beckom (lower rainfall) both in southern NSW; and; representing a winter dominant pattern ‐ Eversley, (higher rainfall), and Bealiba, (lower rainfall), in central Victoria. The objective was to determine if the new candidate cultivars were more likely to persist and to be productive than current commercial cultivars. The study showed that most phalaris and cocksfoot treatments were highly productive in high rainfall years at one or both sites in southern NSW. However, all treatments had become much less productive by the end of the experimental period due to plant loss under hot, dry conditions in the final summer. At Bealiba in central Victoria, cocksfoot was the most productive species with several cocksfoot treatments of both subsp. hispanica and subsp. glomerata still present at the final harvest despite a hot and dry final summer‐autumn. Tall fescue was the most productive species in the two higher rainfall environments (Inverell, Eversley) although most treatments of all species performed well at those sites. Continental tall fescues were more productive on average than Mediterranean tall fescues at the strongly acidic Eversley site. As a result of this work, two of the new cocksfoot candidates (Moroccan Fine and AVH48 Selection) and one of the tall fescue candidates (Summer Active 1) have been licensed for commercial development and release.     

Use of intralesional cisplatin to successfully treat distal limb haemangiosarcoma in a foal

A 4-month old, 200 kg, grey warmblood colt presented for a firm, non painful mass on the distal medial aspect of the left third metatarsus. Excisional biopsy revealed a diagnosis of haemangiosarcoma. Equine haemangiosarcoma is uncommon and only limited reports of successful treatment are available. The prognosis for survival is therefore considered to be poor. After two separate incidences of recurrence with incomplete excision of the tumour, intralesional treatment with cisplatin without excision or debulking was performed on three separate occasions. Intralesional cisplatin injection was performed at monthly intervals for three treatments. Four years post treatment with cisplatin, the horse remained in remission. This case report describes the diagnostic and treatment challenges for successful treatment of a primary haemangiosarcoma on the distal limb of a warmblood foal using intralesional cisplatin chemotherapy.     

Genomic Prediction of Arsenic Tolerance and Grain Yield in Rice: Contribution of Trait-Specific Markers and Multi-Environment Models

Many rice-growing areas are affected by high concentrations of arsenic(As). Rice varieties that prevent As uptake and/or accumulation can mitigate As threats to human health. Genomic selection is known to facilitate rapid selection of superior genotypes for complex traits. We explored the predictive ability(PA) of genomic prediction with single-environment models, accounting or not for trait-specific markers, multi-environment models, and multi-trait and multi-environment models, using the genotypic(1600 K SNPs) and phenotypic(grain As content, grain yield and days to flowering) data of the Bengal and Assam Aus Panel. Under the base-line single-environment model, PA of up to 0.707 and 0.654 was obtained for grain yield and grain As content, respectively; the three prediction methods(Bayesian Lasso, genomic best linear unbiased prediction and reproducing kernel Hilbert spaces) were considered to perform similarly, and marker selection based on linkage disequilibrium allowed to reduce the number of SNP to 17 K, without negative effect on PA of genomic predictions. Single-environment models giving distinct weight to trait-specific markers in the genomic relationship matrix outperformed the base-line models up to 32%. Multi-environment models, accounting for genotype × environment interactions, and multi-trait and multi-environment models outperformed the base-line models by up to 47% and 61%, respectively. Among the multi-trait and multi-environment models, the Bayesian multi-output regressor stacking function obtained the highest predictive ability(0.831 for grain As) with much higher efficiency for computing time. These findings pave the way for breeding for As-tolerance in the progenies of biparental crosses involving members of the Bengal and Assam Aus Panel. Genomic prediction can also be applied to breeding for other complex traits under multiple environments.     

Performance,milk fatty acid composition and behaviour of high-yielding Holstein dairy cows given a limited grazing period

The effects of a limited grazing period on the performance, behaviour and milk composition of high-yielding dairy cows were examined. A total of 56 Holstein cows yielding 44.7 ± 0.42 kg/day were allocated to one of four treatments in one of two, 4-week periods. Treatments were as follows: control (C)—cows housed and offered TMR ad libitum; early grazing (EG)—cows grazed for 6 hr after morning milking then housed; delayed grazing (DG)—cows returned to housing for 1 hr after morning milking followed by grazing for 6 hr, then housed; restricted TMR (RT)—cows grazed for 6 hr after morning milking, then housed and fed TMR at 75% of ad libitum. Intake of TMR was highest in cows receiving C, intermediate in EG and DG, and lowest in RT at 26.9, 23.6, 24.7 and 20.3 kg DM/day respectively. Pasture intake was similar in cows receiving EG or DG, but was higher in RT at 2.4, 2.0 and 3.5 kg DM/day respectively. Milk yield was similar between cows receiving C, EG or DG, but lowest in RT at 45.7, 44.2, 44.9 and 41.7 kg/cow, respectively, while milk fat content of C18:3 n-3 was increased by grazing. Cows in C spent more than 55 min/day longer lying and had three additional lying bouts/day, while lying bouts were shorter than for cows receiving EG, RT or DG. It is concluded that high-yielding cows can be grazed for 6 hr/day with little impact on performance, provided TMR is available ad libitum when housed.     

Wheat grain quality under increasing atmospheric CO2 concentrations in a semi-arid cropping system

We investigated wheat (Triticum aestivum) grain quality under Free Air CO₂ Enrichment (FACE) of 550 ± 10% CO₂ μmol mol⁻¹. In each of two full growing seasons (2008 and 2009), two times of sowing were compared, with late sowing designed to mimic high temperature during grain filling. Grain samples were subjected to a range of physical, nutritional and rheological quality assessments. Elevated CO₂ increased thousand grain weight (8%) and grain diameter (5%). Flour protein concentration was reduced by 11% at e[CO₂], with the highest reduction being observed at the late time of sowing in 2009, (15%). Most of the grain mineral concentrations decreased under e[CO₂] - Ca (11%), Mg (7%), P (11%) and S (7%), Fe (10%), Zn (17%), Na (19%), while total uptake of these nutrients per unit ground area increased. Rheological properties of the flour were altered by e[CO₂] and bread volume reduced by 7%. Phytate concentration in grains tended to decrease (17%) at e[CO₂] while grain fructan concentration remained unchanged. The data suggest that rising atmospheric [CO₂] will reduce the nutritional and rheological quality of wheat grain, but at high temperature, e[CO₂] effects may be moderated. Reduced phytate concentrations at e[CO₂] may improve bioavailability of Fe and Zn in wheat grain.