Soil extracellular enzyme dynamics in a changing climate

Assays for extracellular enzyme activity (EEA) have become a common tool for studying soil microbial responses in climate change experiments. Nevertheless, measures of potential EEA, which are conducted under controlled conditions, often do not account for the direct effects of climate change on EEA that occur as a result of the temperature and moisture dependence of enzyme activity in situ. Likewise, the indirect effects of climate on EEA in the field, that occur via effects on microbial enzyme producers, must be assessed in the context of potential changes in plant and soil faunal communities. Here, EEA responses to warming and altered precipitation in field studies are reviewed, with the goal of evaluating the role of EEA in enhancing our understanding of soil and ecosystem responses to climate change. Seasonal and interannual variation in EEA responses to climate change treatments are examined, and potential interactions with elevated atmospheric CO₂, increased atmospheric N deposition and changes in disturbance regimes are also explored. It is demonstrated that in general, soil moisture manipulations in field studies have had a much greater influence on potential EEA than warming treatments. However, these results may simply reflect the low magnitude of soil warming achieved in many field experiments. In addition, changes in plant species composition over the longer term in response to warming could strongly affect EEA. Future challenges involve extending studies of potential EEA to address EEA responses to climate change in situ, and gaining further insights into the mechanisms, such as enzyme production, stabilization and turnover, that underlie EEA responses.     

Grape seed characterization by NIR hyperspectral imaging

Currently, the time of grape harvest is normally determined according to the sugar level in the pulp of the berry. Nonetheless, the stage of maturation in grape seeds should be taken into account more frequently to decide the appropriate harvest period. There are chemical and sensory analyses available to assess stage of maturation of grape seeds but they are destructive and time-consuming. Hyperspectral imaging is an alternative technology to characterize the grape seeds according to their chemical attributes, and the current work aimed to non-destructively characterize grape seeds in regard of the variety and stage of maturation. For this purpose, 56 samples of seeds from two red grape varieties (Tempranillo and Syrah) and one white variety (Zalema) in two kinds of soil were selected to assess their features based on the reflectance in the near-infrared (NIR) spectra by using prediction models (partial least squares regression) and multivariate analysis methods (principal component analysis and general discriminant analysis). In this study, a reliable methodology for predicting the stage of maturation was developed, and it was shown that it was possible to distinguish the variety of grape and even the type of soil from hyperspectral images of grape seeds.     

Interactions between land-use history and earthworms control gross rates of soil methane production in an overwintering pasture

The effects of earthworms on soil CH₄ emissions remain ambiguous, as previous studies revealed both positive and negative effects on net rates of CH₄ production. These differences may be linked to land-use history such as pasturing intensity, as the treading of livestock and the input of faeces will affect physical and chemical soil characteristics that are important to methanogenic and methanotrophic bacteria. In order to concomitantly measure the effects of earthworms on the activities of both of these bacterial groups, we performed an isotope dilution assay to measure gross CH₄ production and consumption rates. Samples from three soil types, differing mainly in pasture intensity over the past 15 years, were incubated for 8 weeks in the presence or absence of the vermicomposting species Eisenia andrei. Following the incubation, earthworms had a positive effect on gross process rates in the non-pasture control soil, had no effect in the moderate pasture soil, and had a negative effect in the intensive pasture soil. Phospholipid fatty-acid profiles and chemical characteristics of the fresh soil samples suggested that the non-pasture soil would likely produce less CH₄ than the control soil. Likewise, methanogenic specific mcrA gene abundance following the incubation was two orders of magnitude higher in the two pasture soils than in the control soil. The isotope dilution assay revealed, however, higher gross CH₄ production rates in the control soil. It was also found that gross CH₄ transformation rates were neither correlated to net production rates nor to mcrA gene abundance. We discuss the value and limitations of the isotope dilution assay for understanding the factors and underlying mechanisms governing net CH₄ emissions rates from soils.     

Effect of nitric oxide (NO) and associated control treatments on the metabolism of fresh-cut apple slices in relation to development of surface browning

Surface browning is an important cause of deterioration of fresh-cut apples during postharvest handling. ‘Granny Smith’ apple slices treated with NO gas (10 μL/L) and the NO donor compound 2,2′-(hydroxynitrosohydrazino)-bisethanamine (diethylenetriamine nitric oxide (DETANO) (10 mg/L) dissolved in phosphate buffer (pH 6.5) showed delayed development of surface browning during storage at 5 °C and also resulted in a lower level of total phenols, inhibition of PPO activity, reduced ion leakage and reduced rate of respiration but had no significant effect on ethylene production or lipid peroxide level as measured by malondialdehyde (MDA) and hydrogen peroxide levels. The two control treatments of phosphate buffer (pH 6.5) and water dips also had significant effects compared to untreated slices. The relative effectiveness of treatments in extending postharvest life and reducing total phenols, PPO activity, ion leakage and respiration was DETANO > NO gas > phosphate buffer > water > untreated. Apple slices dipped in chlorogenic acid dissolved in water showed surface browning soon after application but dipping in DETANO solution negated the effect of chlorogenic acid whether applied before or after dipping in chlorogenic acid solution while the buffer and NO gas were also effective. It is suggested that an increase in phenols occurs on the apple surface soon after cutting, possibly as a defensive mechanism of the apple to limit damage to surface cells. The effectiveness of the applied treatments to inhibit development of surface browning may relate to their ability to minimize the level of phenols active on the cut surface possibly in conjunction with a reduced PPO activity.     

Homegardens of Andaman and Nicobar,India

The study reports the influence of biophysical and socio-cultural factors on composition, diversity and distribution of plant species in the homegardens of the Andaman and Nicobar archipelago of India. The study also examines component interactions and productivity of the system. Four hundred and thirty homegardens were surveyed from six islands, four from Andaman (South Andaman, North Andaman, Middle Andaman and Little Andaman) and two from Nicobar district (Car Nicobar and Nancowry). In Nicobar, an aboriginal tribe, the Nicobari, predominates. The Nicobaries are Christians. However, people from different parts of the Indian subcontinent were rehabilitated in the Andamans in the mid twentieth century. A mixed culture prevails in South Andaman, but in the other Andaman islands either Bengali or Tamil culture predominates. Biophysically, South Andaman is hilly whereas Nicobar is flat. The other islands lie in between the two extremes. All are similar climatically. Twelve to thirty-four plant species were encountered in the homegardens that were planted, cared for and harvested. These plants categorized as palm, fruit, spice and forest trees, formed a three-storey structure in Andaman and a two-storey structure in Nicobar’s homegardens. The floristic similarity between the homegardens of the Andamans was 82–92%. However, it was only 12–18% between the homegardens of Andaman and Nicobar. Compared to Nicobar, species richness was greater in the homegardens of the Andamans. However, diversity was higher and evenness lower in the homegardens of Nicobar. All plant species in the homegardens of Nicobar are spontaneous in regeneration. For the Andamans, the proportion of spice trees was higher in the homegardens of South Andaman, mango and citrus in North Andaman, and pineapple and vegetables in Little Andaman. High plant diversity in these homegardens serves subsistence needs and provides income to most of the households as well. Net income in the homegardens of Andaman was 6.9 times higher compared to that in the homegardens of Nicobar.     

Effect of pruning Acacia mangium on growth,form and heart rot

Small volumes of timber are now being produced from Acacia mangium plantations in Indonesia. These trees require pruning and thinning to increase the strength and appearance of the wood. However, cut surfaces from pruning are potential infection courts for the entry of decay-causing fungi like heart rot. This study investigated the effects of pruning on stem form and the incidence of heart rot in an 18-month-old plantation of Acacia mangium in South Sumatra. The objectives were to assess whether pruning is associated with an increase in the incidence of heart rot and whether form pruning compared to lift pruning reduced the incidence of heart rot and improved stem form. Form pruning removed 25% of leaf area by removing large branches and those subtending a narrow angle with the stem up to 3 m height, and lift pruning removed 25% of crown length from below. Trees in these treatments were singled before pruning. The third treatment, a control, was not singled and was used to assess base levels of heart rot.No significant difference in diameter increment between the two pruning treatments was found. There was strong evidence that form pruning was associated with better form 18 months after treatment. Trees in this treatment had a reduced number of branches >30 mm diameter and improved stem straightness (reduced kink). Lift pruning reduced average branch size but did not improve stem straightness. No heart rot was detected in any treatment.The results showed that form pruning is likely to have positive benefits on stem straightness and is likely to be effective to any selected pruning height. However a subsequent lift pruning is still considered a requirement. While wounds created from pruning and singling are assumed to have a large impact on the incidence of heart rot, this may not be an issue unless there is a sufficient source of fungi present in the environment to invade the wounds.     

Measuring consumer response to ‘Gala’ apples treated with 1-methylcyclopropene (1-MCP)

Post-harvest apple treatment with 1-methylcyclopropene (1-MCP) was previously found to inhibit fruit ripening but also to inhibit the production of volatile compounds that contribute to apple flavor. The first objective of this study was to determine if consumers could distinguish 1-MCP treated and untreated Gala apples [Malus sylvestris L. (Mill.) var. domestica Borkh. Mansf.] following long-term storage. Chemical analysis showed 1-MCP treated fruit had reduced flavor volatiles compared to untreated fruit. Consumer difference tests showed they could distinguish between 1-MCP treated and untreated fruit. A second objective was to compare consumers’ acceptance for 1-MCP treated to untreated apples. Both 1-MCP treated and untreated apples received high overall liking scores that were not significantly different. Equal numbers of consumers indicated preference for 1-MCP treated and untreated fruit and there was no difference in purchase intent. However, subsets of consumers who eat Gala, Fuji or Red Delicious apples showed preference for untreated over 1-MCP treated fruit compared to consumers who do not eat these varieties.     

Post-harvest storage effects on guayule latex,rubber, and resin contents and yields

Guayule is a new crop being commercialized for hypoallergenic latex production. Because natural processes that occur in the plant following harvest, notably dehydration, result in rapid loss of latex and immediate processing of guayule shrub for latex on a commercial scale is not feasible, storage conditions that maintain latex concentration and yield need to be established. The objective of this study was to determine the effects of different storage conditions on the extractable latex, total rubber, resin, and guayulin A and B contents, and extractable latex, total rubber, and resin yields in harvested guayule shrub. The experiment was established using plants transplanted into the field at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ, USA, on 22 March 2001. A randomized complete block design with four replications was used. Two germplasm lines (11591 and AZ-2) were used for this experiment. Twenty plants of each line were harvested six times (November 2002, March 2003, July 2003, November 2003, March 2004, and July 2004) from each field plot. Two plants of each line were randomly assigned to each of 10 storage treatment combinations reflecting wet, dry, or wet alternated with dry conditions prior to chipping for latex extraction. Extractable latex content, total rubber content, resin content, and guayulin A and B contents were determined after storage and compared with freshly harvested shrub. Plant biomass, latex yield, rubber yield, and resin yield were also determined and compared with fresh harvested shrub. AZ-2 was significantly lower in latex, rubber, and guayulin A content than 11591, and significantly higher in biomass, latex yield, rubber yield, resin content, resin yield, and guayulin B content. The results from this study show that moist storage of harvested shrub prior to dry chipping allows a higher yield of latex. Storing the shrub under moist conditions may allow more flexible harvesting and processing schedules, by limiting post-harvest latex losses and increasing the time interval between harvesting and processing.     

Changes in hydrophilic and lipophilic antioxidant activity and related bioactive compounds during postharvest storage of yellow and purple plum cultivars

Eight plum cultivars (four dark-purple and four yellow) were harvested at the commercial ripening stage, and changes of fruit quality properties were evaluated during cold storage and subsequent shelf-life, with special emphasis on bioactive compounds (phenolics, anthocyanins and carotenoids) and antioxidant activity (TAA). From the eight plum cultivars, four showed the typical climacteric ripening pattern (‘Blackamber’, ‘Larry Ann’, ‘Golden Globe’ and ‘Songold’) while four behaved as suppressed-climacteric types (‘Golden Japan’ ‘Angeleno’, Black Diamond’ and ‘TC Sun’), the latter being described for the first time. At harvest, large variations in phytochemicals and antioxidant activity were found among cultivars in peel and pulp tissues, although phytochemical concentration and antioxidant activity were higher in the peel than in the flesh (2–40-fold depending on the bioactive compound). During storage, increases in total phenolics for all cultivars (peel and pulp), in total anthocyanin content in the peel of the dark-purple plums, and total carotenoids in the peel and pulp of the yellow cultivars were observed. This behaviour of the bioactive compounds was reflected in TAA changes, since hydrophilic-TAA (H-TAA) was correlated with both phenolics and anthocyanins, while lipophilic-TAA (L-TAA) was correlated with carotenoids. L-TAA comprised about 30–50% of the TAA in plum tissues. Carotenoids and phenolics (and among them the anthocyanins) could be the main lipophilic and hydrophilic compounds contributing to L-TAA and H-TAA, respectively. No significant loss of bioactive compounds and TAA occurred during prolonged plum storage. Moreover, for a better evaluation of the antioxidant potential of plums, the contribution to carotenoids should not be overlooked.     

Design properties for molded,corn-based DDGS-filled phenolic resin

With the rapid growth in the ethanol fuel industry in recent years, considerable research is being devoted to maximizing the use of processing coproducts, such as distillers dried grains with solubles (DDGS), typically for livestock diets. Because these residues contain high fiber levels, they may be amendable to incorporation into polymers as well, which is an option that could garner greater economic returns. Thus, the goal of this study was to demonstrate the viability of using corn-based DDGS as a biofiller with phenolic resin, in order to produce a novel biomaterial. DDGS was blended with phenolic resin at four levels (0%, 25%, 50%, and 75%, by weight), and then compression molded at 13.8, 34.5, or 48.3 MPa (1.0, 2.5, or 3.5 tons/in.²) and 157, 174, or 191 °C (315, 345, or 375 F). Molded specimens were then tested for a variety of mechanical and physical properties. Pressure and temperature each had little effect on the resulting properties. DDGS, on the other hand, greatly influenced all of the properties. Tensile yield strengths ranged from 14.5 MPa (2102 psi) to 4.3 MPa (621 psi), while the Young's modulus ranged from 2296 MPa (333,000 psi) to 841 MPa (122,000 psi) as the DDGS content increased. For all time periods studied, water absorption increased as DDGS level increased. Moreover, as DDGS content increased to a maximum of 75%, biodegradability increased from 0% to 38% while the surface hardness decreased 25%. These results were similar to those from other studies that have investigated biofillers. Follow-up studies should aim to optimize the strength of the DDGS-blended resins through the use of coupling agents or other additives.