Research Abstracts

Schreiner, Monika.  Vegetable crop management strategies to increase the quantity of phytochemicals.  European Journal of Nutrition.  2005. v44, 85-94.

Phytochemicals have been demonstrated as active components in reducing the risk of chronic diseases such as cancer and cardiovascular disease; they also act as antioxidants, lower cholesterol, and have anti-thrombotic properties.  The level of phytochemicals in fresh fruits and vegetables can greatly vary depending on cultivar type, crop production practices, and post-harvest treatment.  This paper explores the relationship between such variables and phytochemical levels, studying different brassicas and radishes.  The study found that cultivar type and genetic variation have the most significant affect on phytochemical levels, and ecophysical factors such as climate and irradiation, as well as water and nutrition supply influence the levels as well.  The study discusses the important role of sulfur as a micronutrient to increase amino acid levels, and also cites studies that show reducing nitrogen promotes higher levels of glucosinolates.  The author also cites further potential for increasing glucosinolates and anthocyanins by applying elicitors such as amino acids.

Dillard, C. and German, B.  Phytochemicals: nutraceuticals and human health.  Journal of the Science of Food and Agriculture.  2000. 80: 1744-1756.

This article reviews very specifically the effect certain phytochemicals have on different biological processes, focusing on the health benefits different phytochemicals.  Polyphenols are proven to have strong antioxidant properties.  Terpenoids provide hormonal and growth regulatory functions, as well as protect from disease related to chronic damage and growth dysregulation.  Different phenolic compounds offer a range of health benefits, including preventing high blood pressure, reducing the risk of estrogen-related cancers, and broad spectrum anti-inflammatory and antibactierial properties.  Alkaloids, such as glucosinolates, are activators of liver detoxifying enzymes.

Barberan, F. and Espin, J.  Phenolic compounds and related enzymes as determinates of quality in fruits and vegetables.  Journal of the Science of Food and Agriculture. 2001. 81:8553-876.

Phenolic compounds are plant secondary metabolites that are relevant to the appearance, smell, taste, storage quality, and health-promoting properties of foods.  Health properties include their anti-platelet, antioxidant, anti-inflammatory, antitumoral and oestrogenic activities, which might suggest their ability to prevent coronary heart disease and cancer.   There are many factors which affect the phenolic composition of foods, including genetic, agronomic, and post harvest treatments.

The agronomic factors of note include: calcium deficiencies in apples can lead to ‘bitter pit” development during storage, boron availability affects the phenolic content of plants substantially, the occurrence of betains and Ca in soil induce phenolic metabolism and anthocyanin accumulation in grapes, and silicon deprived plants illustrate more susceptibility to fungus causing powdery mildew.  Also related are the studies finding that abiotic stress is induced by high nitrogen dosages in bean plants, and calcium chloride applications can aid in maintaining membrane integrity in some crops.

Phenolic compounds are also crucially related to the flavor of foods; their presence resulting in the bitter, sweet, pungent, or astringent taste in some foods.  Examples are the bitter phenolics present in hops and citrus fruits, the pungent, ones prevalent in hot peppers, ginger, and turmeric, and volatile ones related to aromas such as vanillin.

Dudareva N., Negre F., Nagegowda D., and Orlova I. Plant Volatiles: Recent Advances and Future Perspectives. Critical Reviews in Plant Sciences. 2006. 25:417-440.

Plant volatiles constitute about 1% of plant secondary metabolites; they act as a means for communication between plants, insects, and herbivores, moving freely through the atmosphere and soil.  Volatiles emitted into the atmosphere can serve to defend plants against herbivores and pathogens by their ability to either directly repel microbes and animals, or attract natural predators of attacking insects/herbivores.  These warning volatiles also induce the emission of similar defensive volatiles by neighboring plants.  Volatiles can also enhance a plants reproductive success by attracting pollinators and/or seed dispersers.  Volatiles emitted from roots can contribute to below ground defense in similar ways: acting as antimicrobial and antiherbivore substances, or attracting enemies of root feeding herbivores.  The presence of volatiles was also found to increase a plant’s ability to withstand injury from extreme temperature fluctuations, and enables continued photosynthesis even in temperature extremes.  The presence of volatiles, and abilities for plants to produce them, greatly increases plants resiliency to a variety of threats.

Oliver, M. Soil and human health: a review.  European Journal of Soil Science. 1997. 48:573-592.

This article discusses the general effects of trace elements on health.  Copper is essential in man, it forms organic complexes and metallopoteins such as haemoglobin,  Copper also aids in blood clotting maturation of connective tissues, and development of bones.  Copper concentration in crops and forages depends on its concentration in soil, soil pH, plant species, crop management and climate.

Fluorine content of soil varies widely because of different parent material. Fluorine is rapidly absorbed by the body, and quickly enters the lattice of bone crystal structure permanently, and stimulates new bone growth.  The link between fluorine and dental health has already been clearly established. 

Iodine is an essential constituent for thyroid development, and goiter- and endemic disease linked to lack of iodine, is well known.  It is stated that only 20% of the I intake by humans comes from water, while the remaining 80% comes from food, leaving the Iodine content of soil as an important factor in human health.  Iodine concentrations in soil are variable, leaching of I from soil is correlated with low organic matter and clay, while more acidic soil increases the adsorption of Iodine.

Selenium is an important component of the enzymes responsible for the antioxidant defense systems of the body.  Selenium occurs naturally in all soils as a trace element - its availability is affected by the presence of other ions in soil: phosphate displaces Se, which leads to an increase uptake by plants.  The addition of lime to soils increases the availability to plants, and soil texture also affects the uptake of Se by plants, with studies finding a negative relation between the soil clay content and Se in plant tissues.

Zinc is a structural component of many enzymes involved in energy and metabolism, and is important for the synthesis and degradation of carbohydrates, lipids, proteins, and nucleic acids.  Zinc deficiency in soil is widespread in many countries, and the availability of Zn depends greatly on pH, with Zn being mobile in acidic soils.