Acta Alimentaria, Vol. 40 (1), pp. 80–86 (2011) DOI: 10.1556/AAlim.40.2011.1.11
EFFECT OF ELEVATED CO2 ON LYCOPENE CONTENT OF TOMATO (LYCOPERSICON LYCOPERSICUM L. KARSTEN) FRUITS L. Helyesa*, A. Lugasib, E. Pélic, d and Z. Péka Department of Horticulture and Technology, Faculty of Agricultural and Environmental Sciences, Szent István University, H-2103 Gödöllő, Páter K. út 1. Hungary b National Institute for Food Safety and Nutrition, H-1097 Budapest, Gyáli út 3/a. Hungary c Institute of Botany and Ecophysiology, Faculty of Agricultural and Environmental Sciences, Szent István University, H-2103 Gödöllő, Páter K. u. 1. Hungary d Plant Ecology Research Group of Hung. Acad. Sci. and Szent István Univ, Inst. of Botany and Ecophysiology, Szent István University, H-2103 Gödöllő, Páter K. u. 1. Hungary
a
(Received: 22 February 2010; accepted: 23 September 2010)
Recently several studies have focused on the antioxidant activity of lycopene such as quenching of singlet oxygen and scavenging of peroxyl radicals. These properties may play a role in the prevention of different cancer and heart diseases. Tomato is one of the most important sources of lycopene. The main information on the effect of environmental parameters on quality and health-retaining constituents of tomato fruit is mostly related to temperature (air- and fruit canopy temperature) and light effects that might provide a stress to the fruit. Nowadays little is know about the direct effect of elevated CO2. The aim of the present work was to evaluate the effects of elevated CO2 in Perspex open top chambers (OTC) on the lycopene content of tomato fruit. Experiments on the effects of elevated CO2 concentrations showed mixed results. In this work it was found that concentrations of lycopene in a fruit decreased significantly when elevated CO2 was used. Elevated nitrogen sources generated only slight, but not significant difference in the lycopene concentration of tomato fruit. Keywords: lycopene, CO2, open top chambers, tomato
Tomato is one of the most cultivated horticultural plants in the world. In 2006, 126 million tonnes of tomatoes were grown on 4.5 million ha worldwide (FAO, 2006), which amount to one seventh of the total vegetable production. The quality of tomato is characterized by many properties, such as colour, fruit shape and size, firmness and texture (Helyes, 1999). Consumer demand for tasty and healthy fruit will increase in the near future. No doubt, the food production chain, from the seed to the consumer’s plate, will have to fulfil that concern (Bánáti, 2006; 2008). Carotenoids, mainly lycopene, are responsible for the attractive red colour of ripe tomato fruit. The lycopene content of tomato fruit can be affected by several factors such as genotype, environmental conditions (mainly: air- and fruit canopy temperature, radiation) growing system (irrigation, fertilisation, grafting, etc.) and maturity stage of fruit (Helyes et al., 2003; Pogonyi et al., 2005; Brandt et al., 2006; Helyes & Lugasi, 2006; Dorais, 2007). During the ripening period, lycopene content of tomatoes increases sharply from the pink towards, fully ripe stage, but no attempts have been made so far to assess the changes of the other antioxidants present in the fruit (Dumas et al., 2003). All-trans configuration gives 95.4% of the total lycopene content in intact cells of fresh tomatoes. During processing a remarkable part of
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Helyes et al.: EFFECT OF ELEVATED CO2 ON LYCOPENE in TOMATO
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trans configuration is converted to a cis-lycopene (Clinton et al., 1996; Clinton, 1998). Brandt and co-workers (2003) observed significantly higher lycopene content in tomatoes harvested from glasshouse 83.0 mg kg–1 f.w. than that of cultivated open-air (59.2 mg kg–1 f.w.), at different harvesting times. During the vegetation season in the temperate climate, like in Hungary, the frequent and severe drought can be considered as one of the main production-limiting factors, which is occurring together with the increased air temperature (Tuba, 1987), UV-B radiation (Takács et al., 1999), ozone flux episodes (He et al., 2007), salination (Murakeözy et al., 2002), environmental pollution, with for instance, heavy metals and polycyclic aromatic hydrocarbon (Ötvös et al., 2003; 2004). The drought stress and its interaction with the other stresses severely influence the photosynthesis, respiration and carbohydrate metabolism even in the drought-tolerant and desiccation-tolerant plants (Maróti et al., 1984; Nagy et al., 1995; Sass et al., 1996). The carotenoids and the carotenoid-related abscisic acid (ABA) have crucial role in the plants’ responses to the water stress (Tuba, 1984; Beckett et al., 2000). Elevated CO2 concentration could ameliorate partly the deleterious effects of various stresses, but responses to stresses under elevated air CO2 concentration were very diverse (Tuba, 2005). In horticultural production the examination on plant responses to CO2 is divided into open field and controlled environment (plant growth chambers and forcing studies) studies. CO2 enrichment of greenhouse crops began in the early 1920s. In spite of this, there was a rather small interest for carbon dioxide enrichment in 1930–40s and was not practiced to any great extent until the late 1950s (Moe, 1984). There have been a large number of reports on plant responses to increased concentrations of atmospheric CO2, however, no definitive picture can be drawn up on the impacts of longterm exposure to high CO2 as yet (Tuba, 2005). Exposure to high CO2 caused increased CO2 assimilation and decreased the rate of transpiration with a resultant increase in water use efficiency (Meidner & Mansfield, 1965; Farquhar & Sharkey, 1982; Sage & Sharkey, 1987). In general total tomato fruit set increased only slightly with CO2 enrichment but the fruit under CO2 enrichment was significantly heavier (Peet & Willits, 1984). Pinto and coworkers (1999) found an increase in melon yield (+20%) due to mainly increased fruit size and not greater number of fruits. On the other hand, CO2 application through irrigation water did not affect the chemical characteristics (Brix°, total acidity and pH) of the fruits at harvest. In storage, the high CO2 atmospheres significantly prevented the rise in ethylene production, total carotenoid and lycopene biosynthesis and slowed down chlorophyll degradation and loss of firmness (Sozzi et al., 1999). 1. Materials and methods 1.1. Species examined, growth conditions and CO2 fumigation The experiment was carried out in the “Global Climate Change and Plants” Long-term Experimental Ecological Research Station in the Botanical Garden of the Department of Botany and Plant Physiology at the Szent István University, Gödöllő, Hungary. In protected area (greenhouse), seeds were sown into propagation boxes on 27th and 25th March 2005 and 2006, respectively. The planting of seedlings with 6–7 leaves was carried out on 12th May 2005 and 15th May 2006. Plant density was about 3.5 plants/m–2. The soil was light, moderately calcareous and sandy. NPK fertilizers were applied at rates of 105, 85 and 175 kg ha–1 at the beginning and 1‰ and 2‰ (increased N supply) nutrient solutions was given at bi-weekly Acta Alimentaria 40, 2011
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Helyes et al.: EFFECT OF ELEVATED CO2 ON LYCOPENE in TOMATO
intervals. We used two processing varieties determined growth-type varieties: Korall in 2005 and Uno in 2006. Harvest dates were: 30th July, 21st August, and 4th September 2005. In 2006 there was only one harvesting date on 3rd September. Perspex open top chambers (OTC) of 120 cm × 120 cm × 130 cm were set up at the beginning of April and CO2 concentrations were kept at ambient (360 µmol mol–1) for the control and at 700 µmol mol–1 for the high CO2 treatment as described by Tuba and coworkers (1996; 1998). An Infralyt-4 IRGA (VEB Junkalor, Dessau, Germany) controlled a magnetic valve and regulated the rate of CO2 flow from the supply cylinders to the chambers. Axial ventilators ensured the mixing of CO2 with air before it entered the chambers through four inlets. Identical ventilation was used in the control chambers. 1.2. Lycopene analysis At least 8–10 fruits from each repetition were washed, cut, mixed, macerated and stored at –18 °C until analysis. Lycopene from homogenized tomato was extracted with n-hexanemethanol-acetone (2:1:1) mixture containing 0.05% BHT. Water-free Na2SO4 was used to remove water traces of the upper part. Optical density of the hexane extract was measured spectrophotometrically at 500 nm against hexane blank (Sadler et al., 1990) by UV-VIS Spectrophotometer Lambda 3B (Perkin Elmer). Concentration of lycopene was calculated using specific extinction coefficient (E1cm1% 3150) (Merck, 1989). 1.3. Statistical analysis Experiment was executed in four replicates, and the results were expressed as the average plus/minus significant difference at P
