Trevor J. Hocking

Traditional uses and potential health benefits of Amorphophallus konjac K. Koch ex N.E.Br.

Amorphophallus konjac (konjac) has long been used in China, Japan and South East Asia as a food source and as a traditional medicine. Flour extracted from the corm of this species is used in Far Eastern cuisine to make noodles, tofu and snacks. In traditional Chinese medicine (TCM), a gel prepared from the flour has been used for detoxification, tumour-suppression, blood stasis alleviation and phlegm liquefaction; and for more than 2000 years has been consumed by the indigenous people of China for the treatment of asthma, cough, hernia, breast pain, burns as well as haematological and skin disorders. Over the past two decades, purified konjac flour, commonly known as konjac glucomannan (KGM) has been introduced on a relatively small scale into the United States and Europe, both as a food additive and a dietary supplement. The latter is available in capsule form or as a drink mix and in food products. Clinical studies have demonstrated that supplementing the diet with KGM significantly lowers plasma cholesterol, improves carbohydrate metabolism, bowel movement and colonic ecology. Standards for the classification of both konjac flour and KGM have been established by the Chinese Ministry of Agriculture, the European Commission and the U.S. Food Chemicals Codex. However, to date, there is no worldwide agreed regulatory standard for konjac flour or KGM. This highlights the need for harmonization of konjac commercial standards to assess and ensure the quality of existing and future KGM products. Despite the widespread consumption of konjac derived products in East and South East Asia, there has been limited research on the biology, processing and cultivation of this species in the West. Most studies performed outside Asia have focussed on the structural characterisation and physicochemical properties of KGM. Therefore, the objective of this monograph is to review the literature covering the ethnic uses, botany and cultivation of konjac corms, together with the health benefits of KGM with the associated requirements for quality control. Possible directions for future research and development and standardisation of production and classification of this versatile natural product will be discussed.

Effect of sulphur deficiency on the growth and metabolism of sugar beet (Beta vulgaris cv Druid)

Sugar beet plants were grown in variations of a nutrient culture system to induce sulphur deficiency. The effect of sulphur deprivation on the growth and metabolism was investigated by measuring leaf area, chlorophyll content, fresh and dry weights, sulphur, nitrogen, sulphate and nitrate concentrations, glutathione and free amino acid concentrations. Both total sulphur and sulphate concentrations were markedly reduced in response to sulphur deficiency, while significant increases in arginine concentration in shoot tissue were observed. Increases were also observed in shoot nitrogen and nitrate concentrations and both shoot and root N/S ratios. These results demonstrate that total sulphur, sulphate S and sulphate as a percentage of total S are suitable indicators of sulphur deficiency in sugar beet. Arginine responds to sulphur deficiency, but its use as an indicator needs validation under field conditions. © 2000 Society of Chemical Industry

Use of Farmers' Indicators to Evaluate the Sustainability of Cropping Systems on Sloping Land in Yunnan Province, China

Diversity in the biophysical and socio-economic attributes of agricultural systems makes them uniquely niche based. Farmers are expert in local biophysical and socio-economic situations and can contribute in developing pragmatic indicators of agro-environmental development. During evaluation of an agricultural research project in Yunnan, China, local farmers were capable of evaluating the efiects of modifled technologies on existing cropping systems and discussed their attitudes to the interventions using their own indicators. Farmers’ response can be grouped into seven major aspects: i) efiects on income, ii) efiects on production resources, iii) efiects on crop management, iv) existing local knowledge about the technology, v) availability of inputs, vi) access to information, and vii) socio-economic conditions of farming households. Farmers concluded that environmental conditions in the experimental catchment in comparison to an adjacent untreated catchment were better in terms of soil and water losses, vegetation cover and natural resources, infrastructures and catchment management, use of environmentally-friendly technologies, and crop productivity. Success in soil and water conservation programmes depends on the efiorts of the farmers and other local users and their greater involvement helps to identify more pragmatic indicators. Furthermore, it increases ownership of the programme, enhances interactions with the project scientists, increases farmers’ awareness of agro-environmental problems and their possible consequences. These development will enable scientists to develop better targeted interventions and increase the likelihood of adoption of tested technologies by local communities. The use of paired adjacent catchments improved evaluation activities and is proposed as good practice for future catchment improvement programmes.

An Evaluation of the Introduction of Modified Cropping Practices in Yunnan Province, China, Using Surveys of Farmers' Households

Abstract Problems associated with land degradation are serious in China. Sloping land in South China has experienced a decline in crop productivity by 30-60% due to soil erosion and it has been predicted that most topsoil will be lost within the next 100 years if current erosion rates continue. Considering these situations, an agro-environmental research and development project (Sustainable Highland Agriculture in South-East Asia – SHASEA) was conducted in a catchment in Yunnan Province, China, to address the objectives of increasing crop productivity in sustainable and environmentally-friendly ways. A range of cropping practices was developed and implemented in a rural upland catchment (Wang Jia). At the end of the project, farmers were surveyed to evaluate project effectiveness. All farmers from Wang Jia Catchment, who were involved in project implementation, were surveyed. A sample of farmers working in an adjacent catchment (not associated with the project) was surveyed for comparative purposes. Farmers had different perceptions of the cropping practices employed. Contour cultivation was preferred and likely to be adopted. Others practices such as straw mulching and intercropping were seen as less appropriate and unlikely to be adopted. Polythene mulch was recognized as effective, but likely to be adopted only if financial returns were favourable. The availability of relevant information had an important impact on the extent of technology testing by farmers and their willingness to adopt the practices in the future.

Temporal and spatial regulation of glucomannan deposition and mobilization in corms of Amorphophallus konjac (Araceae)

PREMISE OF THE STUDY Konjac glucomannan (KGM), the main biologically active constituent of konjac flour extracted from corms of Amorphophallus konjac (konjac), has potential to be used as a nutraceutical (satiety agent) to combat obesity. Here we present the results of an immunocytochemical investigation of the developmental regulation of the deposition and mobilization of glucomannan in corm tissues of konjac, using an antiheteromannan (mannan/glucomannan) antiserum. METHODS The intensity of antibody binding to glucomannan idioblasts at six developmental stages (i.e., dormancy, leaf bud emergence, leaf bud elongation, leaflet emergence, leaf expansion, and shoot senescence) was compared. KEY RESULTS A temporally regulated pattern of glucomannan deposition and mobilization within the glucomannan idioblasts was observed. A source-sink transition in the corm was shown to occur after leaflet emergence, prior to complete expansion of the leaves. Our data also suggest that the mobilization of KGM initiates at the periphery of the corm and proceeds inward toward the center of the corm. CONCLUSIONS This study represents a significant milestone in our understanding of the mechanisms involved in the physiological and biochemical control of KGM biosynthesis, partitioning, storage, and remobilization. Moreover, this information and the methodology presented provide valuable data for future improvement of the yield and productivity of this important crop.

Response of grass leys to applications of calcified seaweed

Abstract Calcified seaweed has long been used as a soil conditioner in northern Europe, but supposed beneficial responses have not been experimentally substantiated. Field and glasshouse studies examined treatment responses on the characteristics of sandy silt loam Hapludalf soils and on the growth and elemental composition of Loliumperenne. Agricultural lime was a treatment in both experiments, being chemically similar to calcified seaweed. Calcified seaweed was applied at 2 t ha‐1 and produced small increases in soil pH and extractable calcium (Ca). Significant increases in Lolium perenne growth were found in field studies after both calcified seaweed and lime applications. Smaller, but consistent, increases in growth were found in glasshouse pot studies. However, only one harvest showed a significant dry weight yield increase after calcified seaweed application compared with the untreated control. In pot studies, increases in soil extractable Ca were associated with increases in shoot elemental Ca. Decreases in shoot zinc (Zn) and manganese (Mn) concentrations were found after both calcified seaweed and lime applications. Total shoot element accumulation of Zn and Mn after calcified seaweed application were similar to those produced by the control, suggesting that decreases in shoot Zn and Mn concentrations resulted from dilution after increased shoot growth. However, total Zn and Mn accumulation decreased after lime application compared to the control and calcified seaweed treatments, probably resulting from fixation of available soil Zn and Mn through greater increases in soil pH.

A comparative assessment of purification techniques for mesophyll protoplasts of Brassica napus L.

The effects of three different general purification protocols have been assessed quantitatively using mesophyll protoplasts of Brassica napus. Within the initial sample two distinct sub-populations were determined. The methods used influenced the ratio of the vacuolated to chloroplastic type protoplast sub-populations. Overall recovery rates of the initial sample varied according to the method used from 38% to 27%, but the relative recovery of the sub-populations varied considerably with a purified ratio of between 1.0:0.78 to 1.0:7.0. Size distribution profiles of the initial and purified populations are also presented.

Agro-environmental project duration and effectiveness in South-east Asia

Considerable emphasis has been placed on developing technologies for agricultural sustainability. Many bilateral projects are working to achieve this outcome. A desk review was conducted to study the importance of project duration for the effectiveness of sustainable agricultural projects. Longer-duration projects were successful in addressing more holistic issues than short projects. However, funding agencies tend to fund shorter-duration projects, so projects become progressively shorter. At the same time, the number of projects implemented each year is increasing. Despite the decrease in total development assistance, increases in project numbers, particularly since 1986, appear to be at the cost of project duration. Short project duration was one of the most cited reasons for not completing essential dissemination activities for wider adoption, whereas longer-duration projects were usually considered more successful in addressing more holistic issues. It is difficult to produce tangible outputs from agricultural and soil conservation projects within five years. Considering the slow changes in the system and in agricultural and environmental sustainability, the authors suggest that project developers should be advised to plan for a minimum of 5–10 years, depending on the nature of activities. It is time for funding agencies to reconsider their tendency to fund shorter-duration projects.

MODE OF ACTION OF CALCIFIED SEAWEED ON GRASSLAND

Calcified seaweed, the particulate remains of a calcareous red algae, is used as a soil conditioner; but little is known of its effects. Two glasshouse pot experiments examined the effects of calcified seaweed application on a Hapludalf (Salwick series sandy silt loam) and Lolium perenne. Experiment 1 examined the effects of different particle sizes of calcified seaweed on soil pH. Particle size analysis showed that 81.59% of particles were 1–4 mm in diameter. Significant (P<0.05) increases in soil pH were only found after the application of particles <1 mm in diameter. Experiment 2 aimed to elucidate the modes of action of calcified seaweed on soil and Lolium perenne. Apparent increases were found in shoot and root growth after calcified seaweed application. Results demonstrated that localized changes in soil pH were established, which reflected application rate and particle size distribution. Subsequent changes in shoot elemental composition were a function of these localized pH changes. Due to the high CaCO3 content of calcified seaweed, changes in nutrient availability were primarily due to the addition of CaCO3 and subsequent soil pH changes. Overall, the effect of calcified seaweed on soils and plants was dependent on application rate, particle size distribution and rate of nutrient release. A continuum in mode of action appeared to exist with application rate. At the low application rate (0.63 t ha;m−1) calcified seaweed appeared to act as a calcium (Ca)-based soil conditioner. At higher application rates, the effects were similar to those associated with calcitic lime.

Soil Erosion and Conservation on Subtropical Arable in Yunnan Province, South-west China

China has one of the world’s most severe soil erosion problems, extensively reviewed by Wen (1993) and Edmonds (1994) (see also this volume, Chapters 11 and 13). The population is putting severe pressures on the soil resource, which supports 22 per cent of the global population on 7 per cent of the world’s cropland (Brown 1984). The productive soil resource is severely restrained by climate. Much of western China, particularly Xinjiang, Gansu, Ningxia and Inner Mongolia provinces, is too arid, while the Qinghai-Tibetan Plateau of the west is also too cold for extensive crop production (Zhao 1986). Hence, most crops are grown in the humid east. Only about 13.5 per cent (130 million hectares) of total land area is cultivated (Wen 1993). Whilst government policy prohibits cultivation of slopes steeper than 28 per cent (Barrows et al. 1982), this limit is often breached to extend crop production. Land resource pressures exerted by 1200 million people are superimposed on diverse environments, which are often geologically and geomorphologically unstable. Therefore, physical factors, such as slope steepness and stability, tectonic activity, rainfall erosivity and soil erodibility interact with anthropogenic activities, producing the complicated erosion problem. Thus, erosion is produced by a complex interplay of environmental and anthropogenic factors.