Athanasios P. Papadopoulos

Tomato (Solanum lycopersicum) health components: from the seed to the consumer

It is widely accepted that a healthy diet is an important factor in preventing chronic diseases, and in improving energy balance and weight management. Studies have shown strong inverse correlations between tomato consumption and the risk of certain types of cancer, cardiovascular diseases and age-related macular degeneration. Because tomato is the second-most important vegetable in the world after potato, this horticultural crop constitutes an excellent source of health-promoting compounds due to the balanced mixture of minerals and antioxidants including vitamins C and E, lycopene, β-carotene, lutein and flavonoids such as quercetin. Improvement in phytonutrients in tomatoes can be achieved by cultivar selection, environmental factors, agronomic practices, stage of ripeness at harvest, and appropriate handling and conditioning all the way from the field to the consumer. The purpose of this paper is to review the recent literature of the main factors that can improve the nutritional quality of tomato and consequently their beneficial role in human diet. The importance of genotype selection and the optimization of environmental conditions (light, temperature, humidity, atmospheric CO2 and air pollutants) for high nutritional value is outlined first, followed by the optimization of agricultural practices (soil properties, water quality, mineral nutrition, salinity, grafting, pruning, growing systems, growth promoters, maturity, and mechanical and pest injuries). The review concludes by identifying several prospects for future research such as modelling and genetic engineering of the nutritional value of tomato.

The influence of plant spacing on light interception and use in greenhouse tomato (Lycopersicon esculentum Mill.) : A review

Light (photosynthetic photon flux density, PPFD) is the most important factor affecting productivity in greenhouse tomato (Lycopersicon esculentum Mill.). Decreases in PPFD and the duration of the light period owing to seasonal changes reduce the fruit yield of greenhouse grown tomato. Manipulation of plant spacing is a possible means to maximise PPFD interception and its efficient use in any crop. This work provides a review of research reports and modelling approaches to explore the mechanisms that control tomato productivity as a consequence of variations in plant spacing. Most of the reports were taken from research carried out with grain and greenhouse fruit vegetable crops. Based on this review, it was concluded that greater fruit yields are possible in narrow compared with wide plant spacing in greenhouse tomato, owing to increased PPFD interception. Plant spacing greatly affected leaf area and canopy photosynthesis in the tomato crop. The main factors responsible for the increase in fruit yield at narrow spacings were greater crop biomass and increased availability of total assimilates for distribution to the fruits. Narrow spacings appeared to have detrimental effects on tomato fruit size.

Impact of western flower thrips (Thysanoptera: Thripidae) on growth, photosynthesis and productivity of greenhouse sweet pepper

Low, medium and high densities of western flower thrips [Frankliniella occidentalis (Pergande)] were established in three greenhouses, in 1994 and 1995, to investigate the effects of thrips on growth, photosynthesis and productivity of greenhouse sweet pepper. Sweet pepper fruit was very susceptible to cosmetic injury which resulted in a reduction of the commercial grade of the fruit (quality). Damage by western flower thrips (WFT) on the fruit was direct and instant. Short periods of high thrips densities resulted in cosmetic damage to the fruit. The major period for fruit damage occurred in the 3rd to 5th weeks before harvest, when the fruit was growing rapidly. Approximately seven thrips per sticky trap per day from weeks #3 to #5 before fruit harvest will result in fruit being downgraded from commercial grade #1 to #2. Impact of WFT on plant growth, photosynthesis and marketable yield was indirect and cumulative. Leaf photosynthesis was reduced when plants were exposed to more than 1200 accumulated larval-days per plant and marketable yield was reduced when exposed to more than 1800 accumulated larval-days per plant. Plants recovered slowly from the thrips damage once yield loss had been detected. Therefore, thrips abundance should be maintained below 1200 larval-days per plant to prevent the negative impact of WFT on plant physiology and yield. The importance of these findings on pest management programs for WFT is discussed.

Effects of three greenhouse cover materials on tomato growth, productivity, and energy use

Abstract Effects of single-layered glass (glass), double inflated polyethylene film (D-poly), and rigid-twin wall acrylic panels (acrylic), as greenhouse covers on tomato ( Lycopersicon esculentum Mill) growth, productivity and energy use were investigated over two spring seasons in 1993 and 1994. There was no significant difference in early marketable yield (harvested until April 30) between the D-poly and glass houses. Early marketable yield in the acrylic houses was similar to that in the glass houses, but higher than that in the D-poly houses in 1994. Mid-season yield in the D-poly houses was lower than in the glass houses. Final marketable yield in the D-poly and acrylic houses was similar to that in the glass houses. Fruit size during the early and mid-season in the D-poly houses was smaller than in the glass or acrylic houses. This reduction in fruit size shifted 6–12% of grade # 1 fruit from extra large to large. Fruit size in the glass and acrylic houses was similar. In 1993, there was a higher BER (blossom-end rot) incidence in the glass houses than in D-poly or acrylic houses, but a higher percentage of grade #1 fruit in the D-poly houses than in the glass or acrylic houses. The D-poly and acrylic houses saved 30% in heating energy compared to the glass houses.

INORGANIC AND SYNTHETIC ORGANIC COMPONENTS OF SOILLESS CULTURE AND POTTING MIXES

The components of soilless growing media and potting mixes used in horticulture are primarily selected based on their physical and chemical characteristics and, in particular, their superior ability to provide simultaneously sufficient levels of oxygen and water to the roots. There is a lot of variability in the origin and physical and chemical characteristics of the substrates used by the horticultural industry. Substrates are divided into inorganic and synthetic organic materials. The organic materials comprise synthetic substrates and natural organic matter. The inorganic substrates can be classified as natural unmodified materials and processed materials. This chapter provides the description of each substrate, which includes information on its production and origin, general information on its applications as a growth medium, or for other purpose. It sheds light on the physical characteristics, such as bulk density (BD), water retention, and hydraulic conductivity, as these properties are essential for proper irrigation management. Furthermore, it describes the chemical characteristics, i.e., composition, stability as affected by pH, cation exchange capacity (CEC), pH, and salinity, as these basic data are required for the proper management of fertilization and irrigation. In addition, it presents information on substrate sterilization, as disease control is a major factor in the successive use of substrates. Finally, it provides information on waste treatment since the potential for environmental contamination is becoming a central issue in intensive soilless cultivation.

Effects of greenhouse covers on seedless cucumber growth, productivity, and energy use

Effects of single-glass (glass), double inflated polyethylene film (D-poly), and rigid twin acrylic (acrylic) panels, as greenhouse covers, on seedless cucumber growth, productivity and energy use were investigated over three spring seasons (1988, 1990 and 1992). The early and final marketable yields of plants grown in D-poly houses were similar to or higher than those grown in glass houses. Also, plants grown in D-poly houses produced a similar or higher percentage of large and a lower percentage of small fruits than the plants grown in glass houses. The early and final marketable yield and percentages of fruit grades were similar in D-poly and acrylic houses; an exception was the early marketable yield in 1992 which was higher in the acrylic houses. Light transmission was the highest in glass houses, intermediate in acrylic houses and the lowest in D-poly houses. Relative humidity was highest in D-poly, intermediate in acrylic, and the lowest in glass houses. The plants in D-poly houses grew and developed faster (more leaves and flowers) than those in glass houses. The leaf size of plants in D-poly houses and glass houses was similar, but the dry matter content and specific leaf weight of plants grown in D-poly houses were significantly lower (40% less) than those in glass houses. Plants in D-poly houses might have acclimated to the low light conditions by reducing specific leaf weight and increasing their light interception efficiency. Plant growth and development in acrylic and D-poly houses was similar. For cucumber production in climatic conditions similar to South Western Ontario, the D-poly greenhouse is strongly recommended, because there is no loss of productivity in comparison with a glass house, while great savings on initial investment and energy use are achieved.

Impact of western flower thrips on growth, photosynthesis and productivity of greenhouse cucumber

Abstract Low, medium and high densities of western flower thrips ( Frankliniella occidentalis (Pergande)) were established in three greenhouses in 1996 and 1998 to investigate effects of thrips on growth, photosynthesis, yield and quality of greenhouse cucumber. Cucumber fruit were very susceptible to direct cosmetic damage by western flower thrips (WFT). High densities of WFT for short time periods significantly increased the number of fruit downgraded from grade #1 to #2. The most vulnerable stage to cosmetic damage was 4–10 days before fruit harvest, when the fruit were growing rapidly. WFT also increased fruit curvature and reduced plant growth, photosynthesis and marketable fruit yield. However, the impact of WFT on plant growth, photosynthesis and marketable yield was mainly cumulative; the impact was less dependent on the density or exposure duration alone, but more on thrips abundance (integration of thrips density over time). Leaf growth, leaf photosynthetic rate, marketable yield were reduced when plants were exposed to more than 700–2000, 2800, 3000 accumulated thrips-days per sticky card, respectively. It was very difficult for cucumber plants to recover from thrips damage once yield loss had taken place. Therefore, it is recommended to control thrips abundance below 700 accumulated thrips-days per sticky card to prevent a negative thrips impact on plant physiology or yield. The impact of WFT on fruit curvature was smaller than on fruit appearance, but more serious than on plant growth and yield. Five-hundred accumulated thrips-days per sticky card would significantly increase fruit curvature. The implications of experimental results from this study for WFT control are discussed.