Plant Food Quality Research Articles

Agroecosystem Management and Nutritional Quality of Plant Foods: The Case of Organic Fruits and Vegetables

Organic and conventional crop management systems differ in terms of the fertilisers and plant protection methods used. Ecological and agronomic research on the effect of fertilization on plant composition shows that increasing availability of plant available nitrogen reduces the accumulation of defense-related secondary metabolites and vitamin C, while the contents of secondary metabolites such as carotenes that are not involved in defense against diseases and pests may increase. In relation to human health, increased intake of fruits and vegetables is linked to reduced risk of cancer and cardiovascular disease. This benefit may be primarily due to their content of defense-related secondary metabolites, since most other constituents of fruits and vegetables either are not unique to these foods or have been shown to not provide health benefits when the intake is increased. A meta-analysis of the published comparisons of the content of secondary metabolites and vitamins in organically and conventionally produced fruits and vegetables showed that in organic produce the content of secondary metabolites is 12% higher than in corresponding conventional samples ( P< 0.0001). This overall difference spans a large variation among sub-groups of secondary metabolites, from a 16% higher content for defence-related compounds ( P< 0.0001) to a nonsignificant 2% lower content for carotenoids, while vitamin C showed a 6% higher content ( P= 0.006). Based on the assumption that increasing the content of biologically active compounds in fruits and vegetables by 12% would be equivalent to increasing the intake of fruits and vegetables by the same 12%, a model developed to calculate the health outcome of increasing the intake of fruits and vegetables was then used to tentatively estimate the potential increase in life expectancy that would be achieved by switching from conventional to organic produce without changing the amount consumed per day, to 17 days for women and 25 days for men.

ENSO episodes modify plant/terrestrial–herbivore interactions in a southwestern Atlantic salt marsh

Hemisphere scale events such as El Niño-Southern Oscillation (ENSO) can alter rainfall regimes worldwide, with important effects on species abundance and distribution. The evidence of ENSO effects on terrestrial communities is, however, restricted to a few ecosystem types. We explored the effects of ENSO episodes on plant/terrestrial–herbivore interactions through changes in the rainfall regime in a southwestern Atlantic salt marsh (Mar Chiquita coastal lagoon, Argentina. 37° 40′S, 57° 23′W). Surveys showed a positive relationship between winter rainfall and the abundance of the wild guinea pig Cavia aperea. The highest salt marsh abundances of C. aperea were associated with rainy periods during El Niño episodes, and the lowest ones were associated with the driest La Niña episodes. Rainfall was negatively associated with marsh sediment salinity, and experiments revealed that increased salinity reduces growth and increases mortality of cordgrass ( Spartina densiflora). Salt increase also causes the highest percentage of dry area in S. densiflora leaves and reduced carbon content, and more salt content and secretion in S. densiflora stems. A factorial experiment in which we manipulated C. aperea presence and salinity along the edges of S. densiflora patches showed that plants can asexually invade unvegetated areas when salinity is reduced and C. aperea is excluded. Conversely, S. densiflora edges retracted when salinity was increased or there was C. aperea herbivory. Changes in nutritional quality of S. densiflora could explain the low herbivory of (and lack of impacts from) C. aperea in plots with high salinity. Thus, plant distribution responds directly to climate oscillations through changes in salt stress, and indirectly, through changes in plant–herbivore interactions. Herbivores respond indirectly to climate oscillations through changes in plant food quality, which suggests that top-down effects increase when bottom-up stressors are relaxed. ENSO events have direct and indirect effects on marsh communities that modulate the relative importance of top-down and bottom-up effects and have a considerable effect on the primary productivity of S. densiflora marshes.

Catastrophic die-off of globally threatened Arabian Oryx and Sand Gazelle in the fenced protected area of the arid central Saudi Arabia

A large number of die-off of globally threatened Arabian Oryx (Oryx leucoryx), and Arabian Sand Gazelle (Gazella subgutturosa marica) were recorded from 1999 to 2008 in fenced Mahazat as-Sayd Protected Area (PA) in western-central Saudi Arabia. Mortalities of animals have been recorded during summer months when the rainfall is negligible or insignificant. Deaths were due to starvation because of reduced availability, accessibility and quality of food plants in the area. In total, 560 oryx and 2815 sand gazelle deaths were recorded since the reintroduction projects began till the end of 2008. Mortalities of animals were higher in 1999-2001, 2006, 2007 and 2008. Grazing of oryx habitat depends on rainfall and animals move over great distances in response to rain. The fence around Mahazat as-Sayd PA prevents natural movements of animals, and artificially concentrates the ungulate populations into possibly unfavourable habitat. The sand gazelle is a highly gregarious and migratory species, moving long distances in search of good quality pastures. Populations of sand gazelle in Central Asia are also known to migrate over large distances, covering several hundred kilometers. It is therefore likely that by preventing natural movements of sand gazelles and oryx, fencing may have reinforced the effects of stressful conditions such as drought. To reduce the catastrophic effects, a Strategy and Action Plan was developed in August 2008 to manage oryx and gazelle within the reserve and with provision for food and water at the five camps in the reserve as emergency plan to minimize mortalities.

Plant foods consumed by Pan: Exploring the variation of nutritional ecology across Africa

It has been shown that differences in resource density and nutrient supply affect variation in ranging patterns, habitat use, and sociality. Among nonhuman primates, chimpanzees (Pan troglodytes) and bonobos (P. paniscus) have often been used as models for the link between social system and habitat ecology. Field reports suggest that resource density is higher in habitats occupied by bonobos (compared to chimpanzee habitats), and in the West (compared to the East) of the range of chimpanzees. In this study we compared diet quality at the level of species and populations using information from nutritional analyses of fruit and leaves consumed by chimpanzees (three) and bonobos (one population). Quality of plant foods was assessed on the basis of a) the concentration of macronutrients, fiber, and anti-feedants, and b) associations of different nutrient components. Overall plant samples collected at each site differed in terms of macronutrient content. However, nutritious quality and gross energy content of food samples were similar suggesting that dietary quality reflects selectivity rather than habitat ecology. The quality of plant foods consumed by bonobos was within the range of chimpanzees and the quality of plant foods consumed by western chimpanzees was not higher than that of eastern chimpanzees. While the results showed significant variation across forests inhabited by Pan, they did not match with geographical patterns between and within Pan species as proposed in previous studies. This suggests that the nutritional quality of the habitat is not always a reliable predictor of the quality of the diet.

Nectar Sugar Limits Larval Growth of Solitary Bees (Hymenoptera: Megachilidae)

The bottom-up effects of plant food quality and quantity can affect the growth, survival, and reproduction of herbivores. The larvae of solitary bee pollinators, consumers of nectar and pollen, are also herbivores. Although pollen quantity and quality are known to be important for larval growth, little is known about how nectar quality limits solitary bee performance. By adding different levels of nectar sugar directly to solitary bee provisions in the subalpine of Colorado, we tested the degree to which larval performance (development time, mass, and survival) was limited by nectar sugar. We found that larval growth increased with nectar sugar addition, with the highest larval mass in the high nectar-sugar addition treatment (50% honey solution). The shortest larval development time was observed in the low nectar-sugar addition treatment (25% honey solution). Neither low nor high nectar-sugar addition affected larval survival. This study suggests that, in addition to pollen, nectar-sugar concentration can limit solitary bee larval growth and development, and nectar should be considered more explicitly as a currency governing foraging decisions related to producing optimally sized offspring. The availability and sugar content of nectar may scale up to affect bee fitness, population dynamics, and plant-pollinator mutualisms.

Differences in food assimilation between two coot species assessed with stable isotopes and particle size in faeces: Linking physiology and conservation

The red-knobbed coot Fulica cristata experienced a dramatic population decline in Spain, where the common coot F. atra does not face conservation problems. This is puzzling because both species have similar ecologies. It has been suggested that habitat alterations affected the quality of food plants, and this impacted differentially both coots. To verify this, we conducted experiments to determine the assimilation efficiency of both species in relation to food quality. Two types of diets differing in fibre content (commercial food and Potamogeton pectinatus) were offered to captive red-knobbed and common coots, during both spring and autumn. We examined variations in faecal particle size among coot species and diets, indicative of the facility with which food can be assimilated, and used the stable isotope technique to study differences between coot species in stable isotope fractionations from consumption to excretion. Faecal particle size was larger in red-knobbed than in common coots when fibre content was high, but was similar when it was low. Faecal particle sizes were larger in autumn, when fibre content was higher, than in spring. In general, δ 15N in faeces of red-knobbed coots was greater than in faeces of common coots. These results suggest that the digestive efficiency of the red-knobbed coot was lower than that of the common coot, and that the differences increased when the fibre content in food plants increased. Managers should try to make available to coots wetland habitat with high quality food, which may be facilitated by prolonging the hydroperiods.

Seasonal variation in the diet of citril finches Carduelis citrinella: are they specialists or generalists?

The seasonal variation of food selection in mountainous citril finches was studied in the Black Forest. citril finches show a strong seasonal variation in quantity and quality of food plants. From November to March, only a few plants have been observed as diet, namely seeds of the germander and the mountain pine (period of food restriction). From April to June, the seeds of a few key food plants such as the dandelion, common sorrel, vernal grass, and mountain pine gain special importance during breeding and the rearing period of the young (period of food specialization). Finally, from June/July to October, citril finches enter into a generalist period with a wide variety of seeds of herbs and grasses (period of food generalization). The changes in food selection are well adapted to the changing resource availabilities and climatic conditions of the Black Forest mountains. In direct comparison to other finches, pure mountain-dwelling species such as citril finches and Syrian serins show a clearly higher seasonal variability in food selection than do lowland species such as goldfinches, linnets, and greenfinches.

Australian Adult Consumers’ Beliefs About Plant Foods: A Qualitative Study

This exploratory qualitative study examined consumers' perceived barriers and benefits of plant food (fruits, vegetables, grains, legumes, nuts, seeds) consumption and views on the promotion of these foods. Ten focus groups were conducted in Melbourne, Australia. Groups consisted of employees of various workplaces, community group members, university students, and inner-city residents. Health-related benefits predominated, particularly relating to the properties of plant foods (e.g., vitamins). Taste, variety, versatility, and environmental benefits were also considered important. The main barriers to eating plant foods were lack of knowledge and skills and length of preparation time. The poor quality of plant foods was also an issue for consumers. Awareness of the promotion of plant foods was generally high. Participants noted that promotions require a stronger practical emphasis with a focus on quick, easy-to-prepare foods and meals. These findings provide insight into effective ways to promote a higher consumption of plant foods.

Metabolic engineering of proanthocyanidins by ectopic expression of transcription factors in Arabidopsis thaliana

Genetic transformation of Arabidopsis thaliana with the Arabidopsis TT2 MYB transcription factor resulted in ectopic expression of the BANYULS gene, encoding anthocyanidin reductase, AHA10 encoding a P-type proton-pump and TT12 encoding a transporter involved in proanthocyanidin biosynthesis. When coupled with constitutive expression of PAP1, a positive regulator of anthocyanin biosynthesis, TT2 expression in Arabidopsis led to accumulation of proanthocyanidins, but only in a subset of cells in which the BANYULS promoter is naturally expressed. Ectopic expression of the maize Lc MYC transcription factor weakly induced AHA10 but did not induce BANYULS, TT12 or accumulation of proanthocyanidins. However, high-level combined expression of TT2, PAP1 and Lc resulted in proanthocyanidin synthesis throughout young leaves and cotyledons, followed by death of the plants 1 to 2 weeks after germination. We discuss these results in relation to engineering proanthocyanidins to improve the quality of food and forage plants.

Evaluation of Quality of Rice Grains by Photoacoustic Imaging

Recently, quality evaluation and control has become increasingly important in biology and agriculture. The evaluation of the quality of food plants has been performed by many inspection methods. To date, the evaluation of the grain of crops by photoacoustic spectroscopy in the infrared region has only been performed for corn. We have developed a method of applying a photoacoustic microscope (PAM) to pollen analysis. In this study, a PAM was used to evaluate the quality of crop grains, rice in this case, for the first time. Due to differences in the absorption of the laser beam, the homogeneity of rice grains was measured and shown as thermal images. The resolution was sufficiently good to evaluate a single grain of rice. This method has an advantage in that it can be used to measure the existence of both the surface and back surface colored regions. In addition to conventional video image evaluation or the macroscopic optical absorption method, PA imaging can enable the evaluation of the quality and condition of rice grains.

Carotenoid biosynthesis in plant storage organs: recent advances and prospects for improving plant food quality

Carotenoids are components of the photosynthetic machinery, intermediates in the biosynthesis of abscisic acid and other apocarotenoids and act as coloured pigments particularly in floral and fruit tissue. Humans benefit in a number of ways from dietary carotenoids present in green leaf tissue and many fruits, seeds, roots and tubers. Carotenoids with a β‐ring end group are required for the synthesis of vitamin A, and deficiency for this vitamin remains a major health problem in some parts of the world. Epidemiological studies suggest that carotenoids also have important roles in a range of diseases including age‐related macular degradation and some cancers. The isoprenoid pathway is described, which leads to the carotenoids via the condensation of five‐carbon isoprenoid units to form a 40‐carbon chain in phytoene. The early part of the biosynthetic pathway involves crosstalk between plastidic and cytosolic components. Desaturation, isomerization, cyclization, hydroxylation and epoxidation of the 40‐carbon phytoene gives the range of carotenoids found in plants. The nuclear‐encoded enzymes for these stages are targeted to plastids, and in some cases, different members of a gene family are active in plastids in different tissue types. Studies on the transgenic manipulation of the pathway, natural and induced mutants, gene silencing and gene and quantitative trait locus mapping are increasingly unravelling the pathway and its control, giving opportunities for directed manipulation of the types and quantities of these nutritionally important compounds in crop tissues used in human and animal diets.

English

The quality of food and food plants can be modified and optimized to meet the nutritional and health needs of at-risk and compromised populations prevalent in most of the developing countries. High rates of malnutrition, infectious disease as well as diet-related diseases such as diabetes and hypertension are prevalent in many developing countries. These are as a result of compromised immune function, inadequate sources of nutritious and quality foods and limited access to healthy and suitable foods. Biotechnology and genetic modification techniques have been proposed and applied for the improvement of the quality of various food crops. These have typically been geared towards increasing yields and pest resistance of cash crops. There is considerably less emphasis however, toward improving quality with regard to fortification or functionality of foods and food plants. Functional foods have nutritional and physiological benefits and are applicable in disease prevention and management. The application of biotechnology techniques for the development of functional food plants with higher levels of bioactive components or increased availability of nutrients would greatly benefit most populations in developing countries and improve the health and nutritional status overall. Key words : Biotechnology, functional foods, food quality, health, developing countries. African Journal of Biotechnology Vol. 2 (12), pp. 631-635, December 2003

Phosphorus–Zinc Interactions in Two Barley Cultivars Differing in Phosphorus and Zinc Efficiencies

Phosphorus (P)–zinc (Zn) interactions in two barley cultivars (Clipper and Sahara) differing in P and Zn efficiencies were investigated in a pot experiment carried out in a growth chamber. A highly calcareous field soil from a semi‐arid region of South Australia was used. Five levels of P addition and three levels of Zn addition were used. Plants were harvested five weeks after emergence. Increase in P supply significantly increased plant shoot biomass and tissue P concentrations in both cultivars, indicating that the soil used is P deficient. Zinc additions with low P additions caused slight decreases in plant biomass. However, Zn addition did increase plant growth when higher levels of P were applied demonstrating the importance of the balance Zn and P supply. Results showed that the genotypic difference between the two cultivars in P uptake efficiency (specific P uptake, SPU) can be altered by Zn–P interactions, and that total Zn uptake by Sahara was higher than Clipper irrespective of P supply. Tissue Zn concentrations decreased significantly with an increase in P supply in both cultivars. Increase in P supply drastically reduced the molar ratio of Zn to P in shoots (MRZP), and addition of Zn compensated for the reduction in MRZP due to P addition. The role of P–Zn interactions in the context of nutritional quality of plant food is also discussed.

Variation in Foraging Behavior and Body Mass in Broods of Emperor Geese (Chen Canagica): Evidence for Interspecific Density Dependence

Abstract Broods of geese spend time feeding according to availability and quality of food plants, subject to inherent foraging and digestive constraints. We studied behavioral patterns of broods of Emperor Geese (Chen canagica) on the Yukon–Kuskokwim Delta, Alaska, and examined how feeding and alert behavior varied in relation to habitat and goose density. During 1994–1996, time spent feeding by Emperor Goose goslings and adult females was positively related to multispecies goose densities near observation blinds, and not to just Emperor Goose density. Similarly, body mass of Emperor Goose goslings was more strongly related (negatively) to multispecies goose densities than intraspecific densities. A grazing experiment in 1995 indicated that most above ground primary production by Carex subspathacea, a preferred food plant, was consumed by grazing geese. Those results demonstrate that interspecific competition for food occurred, with greatest support for goslings whose behavioral repertoire is limited primarily to feeding, digesting, and resting. Although the more abundant Cackling Canada Geese (Branta canadensis minima) differed from Emperor Geese in their preferred use of habitats during brooding rearing (Schmutz 2001), the two species occurred in equal abundance in habitats preferred by Emperor Goose broods. Thus, Cackling Canada Geese were a numerically significant competitor with Emperor Geese. Comparing these results to an earlier study, time spent feeding by goslings, adult females, and adult males were greater during 1993–1996 than during 1985–1986. During the interval between those studies, densities of Cackling Canada Geese increased two to three times whereas Emperor Goose numbers remained approximately stable, which implies that interspecific competition affected foraging behavior over a long time period. These density-dependent changes in foraging behavior and body mass indicate that interspecific competition affects nutrient acquisition and gosling growth, which has a demonstrated effect (Schmutz 1993) on juvenile survival of Emperor Geese. Management of Emperor Geese should consider interspecific relations and densities of all goose species occurring on the Yukon–Kuskokwim Delta, Alaska.

VARIATION IN FORAGING BEHAVIOR AND BODY MASS IN BROODS OF EMPEROR GEESE (CHEN CANAGICA): EVIDENCE FOR INTERSPECIFIC DENSITY DEPENDENCE

Abstract Broods of geese spend time feeding according to availability and quality of food plants, subject to inherent foraging and digestive constraints. We studied behavioral patterns of broods of Emperor Geese (Chen canagica) on the Yukon–Kuskokwim Delta, Alaska, and examined how feeding and alert behavior varied in relation to habitat and goose density. During 1994–1996, time spent feeding by Emperor Goose goslings and adult females was positively related to multispecies goose densities near observation blinds, and not to just Emperor Goose density. Similarly, body mass of Emperor Goose goslings was more strongly related (negatively) to multispecies goose densities than intraspecific densities. A grazing experiment in 1995 indicated that most above ground primary production by Carex subspathacea, a preferred food plant, was consumed by grazing geese. Those results demonstrate that interspecific competition for food occurred, with greatest support for goslings whose behavioral repertoire is limited prim...

Effects of elevated atmospheric carbon dioxide on insect–plant interactions

Effects of elevated atmospheric carbon dioxide on insect–plant interactions

Determinants of seasonal feeding of the generalist snail Arianta arbustorum at six sites dominated by Senecioneae.

We investigated the diet constituents of Arianta arbustorum by means of faecal analysis and regressed their quantity on the availability and quality of food plants. We studied six sites, all dominated by plants from the Asteraceae tribe Senecioneae, early and later in the growing season, predicting that the snail's food choice would be determined by the presence of the different secondary compounds found in the Senecioneae. The snails consumed less green plant material and more leaf litter in May than in July. Plant water and nitrogen content were higher in May. For the May samples, regressions were only significant at sites that excluded Adenostyles alliariae and Adenostyles alpina; in July, the regression fit was higher at all sites. Of the measured plant parameters, only quantity (availability) was a consistently significant variable in the regressions. Circumstantial evidence suggested that plant secondary compounds had a major influence on snail food choice: fresh-plant consumption increased over the season, as the concentration of many secondary compounds decreased; both plant availability and quality could only explain about half of the observed variation in snail feeding, which argues for other hidden factors influencing snail feeding; the dynamics of feeding of the various senecionean plants were such that A. alliariae and Senecio sp. had a seasonal acceptance whereas Petasites albus was always and A. alpina never accepted, and, finally, the detection of a number of snail-deterrent fractions in A. alpina leaves, a plant which was never found to be consumed in this study.

Chemosensory discrimination of plant and animal foods by the omnivorous iguanian lizard Pogona vitticeps

Most iguanian lizards are insectivores that do not use chemical cues sampled by tongue-flicking to identify prey before attacking, but the sole iguanian herbivore previously studied did so. To investigate the effects of a partially herbivorous diet on responses to food chemicals, I conducted an experiment to determine whether the omnivorous bearded dragon (Pogona vitticeps) has a similar ability. Chemical stimuli from crickets and carrots, both preferred foods, and alfalfa sprouts, and deionized water (a nonpreferred food and odorless control, respectively) were presented on cotton-tipped applicators. The lizards responded more strongly to both preferred foods than to the controls, performing more tongue flicks and biting the cotton in a greater number of trials. It is hypothesized that lingually mediated food-chemical discrimination is useful to herbivorous and omnivorous lizards for identifying plant and animal foods and for evaluating the quality of plant foods. The insectivorous ambush foragers ancestral to P. vitticeps could not locate prey by tongue-flicking repeatedly at an ambush post and do not exhibit prey-chemical discrimination. Adding plants to the diet altered the selective milieu because plants approached using visual cues can be evaluated using chemical cues, allowing the evolution of the ability to discriminate between plant-food chemicals. The ability to identify animal prey by tongue-flicking may have evolved through correlated evolution with chemosensory identification of plants or specifically for locating or identifying immobile prey.

The Nutritional Enhancement of Plant Foods in Europe ‘NEODIET’

The NEODIET concerted action, funded under the EU FAIR programme, has focussed for the past two years on evaluating the strategies for the improvement of the nutritional quality of plant foods. These strategies involve the enhancement of key metabolites through the application of conventional plant breeding and genetic engineering, as well as the application of newer approaches to food processing. This paper focuses on the benefits of improving the nutritional quality of plants by the enhancement of the beneficial phytochemicals directly in the plant rather than by the addition of essential nutrients to processed foods as has been conventionally undertaken. Examples of the disadvantages of fortifying plant foods are given. The role of food technology in improving the bioavailability of some nutritional constituents, and thereby improving the overall quality of the food, is illustrated with reference to the carotenoids. The importance of structure of the plant metabolite in determining nutritional quality is also illustrated with reference to the effects of structure on the bioavailability and biological effectiveness of plant flavonoids.

Chemosensory discrimination of plant and animal foods by the omnivorous iguanian lizard &lt;i&gt;Pogona vitticeps&lt;/i&gt;

Most iguanian lizards are insectivores that do not use chemical cues sampled by tongue-flicking to identify prey before attacking, but the sole iguanian herbivore previously studied did so. To investigate the effects of a partially herbivorous diet on responses to food chemicals, I conducted an experiment to determine whether the omnivorous bearded dragon (Pogona vitticeps) has a similar ability. Chemical stimuli from crickets and carrots, both preferred foods, and alfalfa sprouts, and deionized water (a nonpreferred food and odorless control, respectively) were presented on cotton-tipped applicators. The lizards responded more strongly to both preferred foods than to the controls, performing more tongue flicks and biting the cotton in a greater number of trials. It is hypothesized that lingually mediated food-chemical discrimination is useful to herbivorous and omnivorous lizards for identifying plant and animal foods and for evaluating the quality of plant foods. The insectivorous ambush foragers ancest...