A. Elia

A survey of nitrate and oxalate content in fresh vegetables

A survey of nitrateONO ˇU and oxalate ((COO ˇ )2) content in fresh vegetables was conducted in Bari (Italy) over 15 months (from March 1994 to May 1995). A total of 327 samples (edible portions and related sub-samples) were taken from 26 different vegetable types on the wholesale fruit and vegetable market. The data revealed that leaf vegetables (namely rocket, celery, parsley and spinach) contained higher levels of nitrate than bulb, root, shoot, inflorescence and tuber vegetables. Higher oxalate levels were found in spinach and Swiss chard. Based on consumption data for the whole population provided by the National Institute of Nutrition, daily nitrate intake from vegetables was calculated to be 71 mg. Over 30% of nitrate intake was derived from the consumption of lettuce and Swiss chard. # 1999 Society of Chemical Industry The presence of nitrate in vegetables, as in water and generally in other food products, is a serious threat to mans health, although recent research has shown that nitrate also has beneficial effects on health related to its role in the bodys mechanism against pathogenic micro-organisms. 3 The harmful effects of nitrate are related not so much to its toxicity, which is low, but to the dangerous compounds that are synthesised in the organism. Indeed, the most serious danger comes from nitrite which is produced by nitrate reduction and which can lead to methaemoglobinemia or form nitrosamines and nitrosamides by reacting with amines and amides, whose carcinogenic action is well known. 4,5

Nitrogen nutrition, yield and quality of spinach

When grown in solution culture spinach plants confirmed the preference toward NO 3 - nutrition and showed heavy toxicity to NH 4 + . In open field condition the highest yield was achieved with the ammonium sulphate in Bari (autumn-winter cycle-110 days) and with calcium nitrate in Policoro (winter-spring cycle-64 days). By increasing N level, yield, nitrates and oxalates leaf content increased. Oxalate content was not affected by nitrogen form. Remarkable differences were observed between leaf petiole and blade in nitrate (4062 vs 925 mg kg -1 of fresh mass) and oxalate (1051 vs 6999 mg kg -1 of fresh mass).

EFFECT OF SOLUTION NITROGEN CONCENTRATION ON YIELD, LEAF ELEMENT CONTENT, AND WATER AND NITROGEN USE EFFICIENCY OF THREE HYDROPONICALLY-GROWN ROCKET SALAD GENOTYPES

Two species of rocket salad, Eruca vesicaria L. subsp. sativa Miller and Diplotaxis tenuifolia L. DC, were grown hydroponically in a growth chamber with two nitrogen levels (1 or 8 mM N) to evaluate nitrate accumulation and nitrogen use efficiency. One ecotype of Eruca and two of Diplotaxis were used. Nitrogen (N) increased leaf production and the contribution of leaves to the total dry mass production in E. vesicaria but not in D. tenuifolia, and emphasized leaf area differences between the two species. The two species also showed differences in the inorganic anions and N content. D. tenuifolia ecotypes accumulated more NO3 than E. vesicaria (7.7 vs. 4.7 g kg−1 fresh mass). By increasing N concentration in the nutrient solution, NO3 content in leaves expressed on fresh mass basis increased in both species by 52%. Nitrogen use efficiency was greater in E. vesicaria than in D. tenuifolia (19.0 vs. 18.0), and decreased with increasing nitrogen in the nutrient solution (19.0 vs. 17.6).

Fertilization strategies for lowering nitrate content in leafy vegetables: chicory and rocket salad cases

Abstract Studies have been carried out to evaluate whether chicory (Cichorium intybus L.) and rocket salad [Eruca vesicaria (L.) Cav. subsp. sativa (Mill)] nitrate (NO3) content can be reduced by decreasing nitrate‐nitrogen (NO3‐N) in the nutrient solution or by partially replacing it with ammonium‐nitrogen (NH4‐N) (chicory only) few days before harvest. Soilless culture method was used applying two levels of NO3 for chicory (2 and 4 mM NO3) and only one for rocket (2 mM NO3). Five (rocket) and six (chicory) days before harvesting, half of the plants were grown always in the same solutions, while the others were grown in a solution with 0.25 mM N (rocket and chicory transferred from 2 mM N) or in a solution where 3/4 of NO3‐N were replaced with NH4‐N (chicory transferred from 4 mM N). Two cultivars of chicory were used. ‘Clio’ hybrid had larger leaf area, but lower dry mass and NO3 concentration than ‘Frastagliata’ chicory. For rocket and chicory alike, the change of nutrient solution five or six days bef...

Subirrigation vs drip-irrigation: Effects on yield and quality of soilless grown cherry tomato

Summary This research was carried out with the aim of comparing drip-irrigation with the trough bench technique of growing a cherry tomato crop, in terms of i) pH and EC of the substrate, ii) production and quality of the fruits and iii) efficiency in the use of the water. In the latter system, pots of opaque plastic with different characteristics were also used: i) with six bottom holes for subirrigation and without risers on the bottom; ii) with four bottom holes and with 3 mm risers on the bottom; iii) with a furrow cross on the bottom and with eight holes and 3 mm risers. This last pot was also used for the drip-irrigation. With both the fertigation methods the EC of the substrate showed a similar pattern over time in the lower and middle layers (always below 3 dS m–1), whereas in the upper layer of the substrate it increased during the growing cycle with higher values with subirrigation compared with drip-irrigation, reaching 7.7 and 3.4 dS m–1, respectively. The pots without risers used for the subirrigation showed the highest variations and values of EC of the recirculating nutrient solution, and the pots with risers and four holes the lowest. Tomato yield was lower with subirrigation than with the traditional free drainage drip-irrigation technique, but the quality was higher (dry matter, total soluble solids, and titratable acidity). Furthermore, with subirrigation the most frequent size class of the fruits was that with a diameter between 25 and 35 mm (considered optimal for cherry tomato), while with the open cycle it was that greater than 35.mm. No significant differences emerged between the three pot types. The water efficiency of the system was greater with subirrigation than with drip-irrigation. To produce 1 kg of fruits, 41 l of nutrient solution were necessary with the subirrigation (closed system) and 59 l with the drip-irrigation (open system).

Comparison between nitrate and ammonium nutrition in fennel, celery, and Swiss chard

Abstract To evaluate the chance to reduce leaf NO3 content and to increase capability to use NH4‐N even in the absence of NO3‐N in the nutrient solution, plants of two Apiaceae species, fennel (Foeniculum vulgare Miller var. azoricum Mill. Thell.) and celery (Apium graveolens L. var. dulce Mill. Pers.), and of one species of Chenopodiaceae, Swiss chard (Beta vulgaris L. var. vulgaris), were hydroponically grown in a growth chamber with three different NH4‐N: NO3‐N (NH4: NO3) ratios (100: 0,50: 50, and 0: 100), but with the same total N level (4 mM) for 14 days. Swiss chard growth was inhibited by NH4 nutrition and reached the highest values with the NH4: NO3 ratio 0: 100. For all the morphological and yield features analyzed, fennel and celery resulted to be quite unresponsive to nitrogen (N) chemical form. Water use efficiency increased in Swiss chard and decreased in fennel and celery with the increase of NO3‐N percentage in the nutrient solution. The dependency of N uptake rate on shoot increment per u...

Morphological and qualitative characterisation of globe artichoke head from new seed‐propagated cultivars

BACKGROUND Three new artichoke seed-propagated hybrids (Tempo, Opal and Madrigal) were compared with two standard cultivated varietal types [Catanese and Violet du Provence (VP)] in terms of head morphology, processing performance, nutritional or technological qualitative traits, in order to define their best use. RESULTS Compared to the other genotypes, Opal and Madrigal had more rounded, heavier, larger heads, higher processing yield (>400 g of heart kg(-1) raw head) and lower total phenol (TP) content (2.4 g of gallic acid equivalents kg(-1) FW). VP gave a higher processing yield than Catanese and showed the highest TP content (6.5 g kg(-1) FW). Tempo hearts were more similar to those of VP in biometrical and chemical terms (P, Na, K, Ca); they had the highest dry matter content (163 g kg(-1) FW) and the waste left after peeling had the highest TP content. CONCLUSIONS Hybrid artichokes, especially Opal and Madrigal, appear more suitable for the processing industry and also for fresh-cut production due to their highest processing yield and lowest total phenol content. Because of its high total phenol content, Tempo waste represents a possible source of natural antioxidant in the pharmaceutical field and in the food industry (as a food additive).

Ammonium and nitrate influence on artichoke growth rate and uptake of inorganic ions.

Abstract Artichoke plants (Cynara scolymus L.) were grown in a growth chamber in a modified Hoagland solution for seven weeks to determine the influence of ammonium:nitrate (NH4:NO3) ratio (100:0, 70:30, 30:70 and 0:100) on growth, water use, and the uptake of nitrogen (N) and inorganic anions and cations. Typical pH changes were recorded: the nutrient solution became acidified with NH4 or NH4:NO3 nutrition; pH increased when NO3 was the only N source. Ammonium‐fed plants (100:0 ratio) were stunted, with signs of marginal leaf necrosis, progressive wilting of leaves and poor root growth. After 49 days, leaf area was 77, 998, 2,415, and 1,700 cm2 and dry weight was 1.0, 12.9, 38.0, and 26.0 g/plant, with NH4:NO3 100:0, 70:30, 30:70, and 0:100, respectively. Leaf area ratio (LAR) was lower in plants supplied solely with NO3 than in those with mixed NH4‐NO3. Increasing NO3‐N percentage in the nutrient solution increased water use efficiency (WUE): 623, 340, and 243 mL of water were necessary to produce 1 g o...

Changes in nitrate accumulation and growth of endive plants during light period as affected by nitrogen level and form 1

Abstract Endive plants (Cichorium endivia L. var. crispum Hegi) were hydroponically grown in a growth chamber to assess, 7 and 14 days after beginning of treatments (DAT), the variation of leaf nitrate (NO3) accumulation and growth during the light period in relation to both nitrogen (N) availability (8 and 16 mM) and form percentage ratio [50:50 and 0:100 ammonium (NH4):NO3] in the nutrient solution. Both 7 and 14 DAT, fresh weight and leaf area linearly increased during the light period without influence of N treatments. Dry matter (d.m.) percentage increased over the 12 hours of light. Leaf NO3 concentration decreased during the light period more with 50:50 than with 0:100 NH4:NO3 ratio: 7 DAT NO3 decreased by 25% with the former N treatment and only by 4% with the latter. After 7 days more, the difference between the two N form ratios was more evident: NO3 decreased by 12% with the mixed N form, while increased by 10% with 100% NO3‐N in the nutrient solution. Nitrate leaf concentration was higher with...

Nutritional, Biophysical and Physiological Characteristics of Wild Rocket Genotypes As Affected by Soilless Cultivation System, Salinity Level of Nutrient Solution and Growing Period

With the aim of defining the best management of nutrient solution (NS) in a soilless system for obtaining high quality baby-leaf rocket, the present study focuses on two wild rocket genotypes (“Nature” and “Naturelle”), grown in a greenhouse under two Southern Italy growing conditions—autumn-winter (AW) and winter-spring (WS)—using two soilless cultivation systems (SCS)—at two electrical conductivity values (EC) of NS. The SCSs used were the Floating System (FS) and Ebb and Flow System (EFS) and the EC values were 2.5 and 3.5 dS m−1 (EC2.5; EC3.5) for the AW cycle and 3.5 and 4.5 dS m−1 (EC3.5; EC4.5) for the WS cycle. The yield, bio-physical, physiological and nutritional characteristics were evaluated. Higher fresh (FY) (2.25 vs. 1.50 kg m−2) and dry (DY) (230.6 vs. 106.1 g m−2) weight yield, leaf firmness (dry matter, 104.3 vs. 83.2 g kg−1 FW; specific leaf area, 34.8 vs. 24.2 g cm−2) and antioxidant compounds (vitamin C, 239.0 vs. 152.7 mg kg−1 FW; total phenols, 997 vs. 450 mg GAE mg kg−1 FW; total glucosinulates-GLSs, 1,078.8 vs. 405.7 mg kg−1 DW; total antioxidant capacity-TAC, 11,534 vs. 8,637 μmol eq trolox kg−1 FW) and lower nitrates (1,470 vs. 3,460 mg kg−1 FW) were obtained under WS conditions. The seasonal differences were evident on the GLS profile: some aliphatic GLSs (gluconapoleiferin, glucobrassicanapin) and indolic 4-OH-glucobrassicin were only expressed in WS conditions, while indolic glucobrassicin was only detected in the AW period. Compared with EFS, FS improved leaf firmness, visual quality, antioxidant content (TAC, +11.6%) and reduced nitrate leaf accumulation (−37%). “Naturelle” performed better than “Nature” in terms of yield, visual quality and nutritional profile, with differences more evident under less favorable climatic conditions and when the cultivars were grown in FS. Compared to EC2.5, the EC3.5 treatment did not affect DY while enhancing firmness, visual quality, and antioxidant compounds (TAC, +8%), and reducing the nitrate content (−47%). The EC4.5 treatment reduced FY and DY and the antioxidant content. Despite seasonal climatic condition variability, FS and the moderate salinity level of NS (3.5 dS m−1) can be suggested as optimum.