Irrigation with saline water affects tomato fruit quality. While total fruit yield decreases with salinity, inner quality characterized by taste and health-promoting compounds can be improved. For a detailed description of this relationship, the influence of three different salt levels [electrical conductivity (EC) 3, 6.5, and 10] in hydroponically grown tomatoes was investigated. Rising salinity levels in the nutrient solution significantly increased vitamin C, lycopene, and beta-carotene in fresh fruits up to 35%. The phenol concentration was tendentiously enhanced, and the antioxidative capacity of phenols and carotenoids increased on a fresh weight basis. Additionally, the higher EC values caused an increase of total soluble solids and organic acids, parameters determining the taste of tomatoes. Total fruit yield, single fruit weight, and firmness significantly decreased with rising EC levels. Regression analyses revealed significant correlations between the EC level and the dependent variables single fruit weight, total soluble solids, titrable acids, lycopene, and antioxidative capacities of carotenoids and phenols, whereas vitamin C and phenols correlated best with truss number, and beta-carotene correlated best with temperature. Only pressure firmness showed no correlation with any of the measured parameters. As all desirable characteristics in the freshly produced tomato increased when exposed to salinity, salinity itself constitutes an alternative method of quality improvement. Moreover, it can compensate for the loss of yield by the higher inner quality due to changing demands by the market and the consumer. This investigation is to our knowledge the first comprehensive overview regarding parameters of outer quality (yield and firmness), taste (total soluble solids and acids), nutritional value (vitamin C, carotenoids, and phenolics), as well as antioxidative capacity in tomatoes grown under saline conditions.

Multielement isotope ratio analysis was checked for its suitability as a means for the discrimination between agricultural products from integrated/conventional or organic production, respectively. Differences were mainly found for delta15N-values. Paprika and tomatoes from organic production in greenhouses showed delta15N-values above+7 per thousand, whereas corresponding products from conventional cultivation had delta15N-values near 0 per thousand. Lettuce, onions, cabbage and Chinese cabbage from field production had delta15N-values in the range of+5 to+6 and+5.5 to+7.5 per thousand, respectively (conventional and organic production); these overlapping differences do not permit a reliable discrimination. The same is true for wheat, showing average delta15N-values of+2.3+/-1.0 and+3.6+/-1.6 per thousand, respectively. The unexpected relative high 15N-enrichments of vegetables from integrated production are discussed as originating, at least partially, from 15N-enrichment in the soil by NH3 evaporation and denitrification.

In this paper we discuss the use of isotope ratios as indicators of organic production. Few studies have investigated the influence of plant nutrition on the isotopic signatures of plants. As plant nutrition is often significantly different between integrated and organic production systems the isotope ratios in the plants may reflect this. Plant samples from a 2-year field-experiment were analyzed for 15 N, 13 C and 34 S content of the bulk-material and 18 O-content of the leaf water. In this experiment cabbages (Brassica oleracea v. capitata f. alba cv. Rolly), onions (Allium cepa cv. Alisa Craig), lettuces (Lactuca sativa v. capitata cv. Ponchito) and Chinese cabbage (Brassica pekinesis cv. Parkin) were cultivated according to good agricultural practices for integrated and organic production. No differences in the d 34 S and d 18 O values of the plants grown under the two production systems were observed. The organically produced vegetables were significantly enriched in 15 N and depleted in 13 C compared to those grown under the integrated system.

We compared five new carrot cultivars with a conventional cultivar in consideration of their content of carotenoids, phenolics and according antioxidative capacity. We chose the following cultivars: orange, white, yellow, red, solid-coloured purple and purple with an orange core. Examinations were conducted over two cultivation periods (2003 and 2004). The white, yellow and solid-coloured purple cultivars showed quite low contents of carotenoids, but the solid-coloured purple contained most phenolic compounds. The red cultivar was the only that contained lycopene. The content of carotenoids varied slightly between the two years; alpha-carotene showed noteworthy differences in the orange cultivar and the purple cultivar with an orange core. The higher alpha-carotene content resulted in a higher antioxidative capacity. Also, the lycopene content in the red cultivar was higher in 2004 than in 2003, which again lead to an increased antioxidative capacity. In the case of phenolics, higher values were found for the purple-coloured cultivars in 2004, which only in the case of the purple cultivar with an orange core, however, led to a higher antioxidative capacity.

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