Effect of Two Greenhouse Covers on Growth, Dry Matter Content and Tomato Fruit Quality L. Jarquin-Enriquez, E. Mercado-Silva and E. Castaño-Tostado Departamento de Investigación y Posgrado en Alimentos Facultad de Química. Universidad Autónoma de Qro. Qro Mexico Keywords: Tomato, growth, dry matter, greenhouse cover, Gompertz model, fruit quality Abstract The aim of this work was to evaluate the effect of two greenhouse cover (glass and plastic) and two crop season (autumn and winter) on growth, dry matter accumulation and fruit quality of Beefsteak type tomato cv. 716 grown in commercial greenhouses. The equatorial diameter of the fruit was measured to evaluate its growth over a seven week period; dry matter accumulation was measured for the same period of time while fruit quality was determined at the end of each season. Mean daily temperatures and overall radiation for each greenhouse were recorded. Daily temperatures in the greenhouses were higher for glass cover compared to those with plastic cover, although both were within the optimal range for tomato growth (2-24 C). The amount of light was greater with plastic than glass during the two seasons. Fruit growth showed a sigmoid type curve and fitted the model proposed by Gompertz to predict population growth. Coefficient a or maximum growth was not significantly affected by treatments. Coefficient b or exponential growth rate, and final exponential growth (Coefficient c ), were higher in tomato plants grown in a glass covered greenhouse during the autumn. The greater rate of growth in the glass cover was due to the fact that the mean temperatures were close to the highest optimal limit for the fruit growth and that the transmittance of the was also higher. Statistical analysis of dry matter content in the tomatoes indicated that the season factor was very significant, showing that winter fruit had higher content of dry matter during the final stages of growth. Production of high quality fruit ( Premium ) was high in both types of cover; nevertheless, in the autumn both covers showed the same values for quality and in the winter, the plastic cover showed a higher percentage Premium fruit quality. INTRODUCTION Potential for high yield in tomato (Lycopersicon esculentum Mill.), has increased over the past years due to advances in soilless culture and the optimization of growing environments using computer controlled greenhouses (Ho, 1996) allowing optimal production and quality. Air temperature, humidity and leaf temperature inside the greenhouses can be affected by light transmittance of the covering material and its insulating properties (Noble and Holder, 1989; Papadopoulus and Hao, 1997) generating a particular microclimate that could affect the growth, development and yield crops (Papadopoulus and Hao, 1997; Dorais et al., 22). From all the solar radiation energy, the covers must allow the entry of the most amount of short length waves between 4 and 7 nm for optimal developments of plants. At this range the light is transferred to the photosynthesized products (Matallana and Montero, 1988) and they influence the growth and quality of the vegetables. However, the amount of solar energy received depends on the season (Serrano, 1994; Pearce et al., 1993b). Glass cover is more transparent to solar radiations (short wave), compared to plastic covers, and opaque to the lengths of long wave radiations emitted by the plants and soil at night. This means that the heat loss at night is much lower in glass covers than plastic covers (Serrano, 1994). Proc. IS on Soilless Cult. and Hydroponics Ed: M. Urrestarazu Gavilán Acta Hort. 697 ISHS 25 481
The aim of this work was to evaluate the effect of two greenhouse covers used and two crop seasons (autumn and winter) on growth, dry matter content and fruit quality of tomato plants grown in commercial greenhouses. MATERIALS AND METHODS This study was conducted from autumn 23 to winter 23-24. Beefsteak tomato plants cv. 716 were grown in 5 commercial greenhouses, 4 of them covered with plastic (.5 ha each one) and 1 covered with glass (2 ha) divided in 4 zones of.5 ha each one. Mean daily temperatures and overall radiation were measured using a PRIVA environmental computer (Priva Computers Inc. ). At fruit set date, 2 fruits were labeled for growth measurement in each greenhouse. At 7 days intervals during the development period (49 days), the equatorial diameter of each fruit was measured, with this value was calculated the increased in fruit volume over time assuming that fruits were spherical, Gompertz function was fitted to each data set expressed by the following equation (Adams et al., 21). e volume = ae Where a is a constant and represents the maximum growth, b is the linear growth rate, c is the restriction at b and t represents the evaluation time. To obtain dry matter content, simultaneously at the growth measurement, 6 fruits with similar diameter were harvested and dried at 7 C for 48 hours (Lopez et al., 1996). Total yield in each greenhouse was classified and packed in grades quality ( Premium, First Class and Nacional ) according to the size and external appearance of each fruit following the guidelines of the company. RESULTS AND DISCUSSION Mean daily temperature inside of greenhouses were higher for glass covers compared with plastic covers (Fig. 1), although both were within the optimal range for tomato growth (2-24 C) (Serrano, 1994). The amount of light was greater with plastic cover than glass cover during the two seasons (Fig. 1). The curves of fruit growth showed a sigmoidal behavior coinciding with literature reports (Monselise et al., 1978; Chamarro, 1995; Ho and Hewitt, 1996) and they fitted significantly to the model proposed by Gompertz to predict population growth (Fig. 2). A statistical analysis of the coefficients of this model (Table 1) indicated that the maximum growth (coefficient a ) was not affected by the treatments while the linear growth rate (coefficient b ) as well as restriction at linear growth (coefficient c ), were higher in tomato plants grown in a glass covered greenhouse during the autumn. The coefficient b, showed a highly significative effect of the interaction cover x season. This effect seems to be explained by the fact that the mean daily temperature in autumn was higher and near to the superior limit for the tomato growth, in the microenvironment generated for glass cover; in the winter this was in the microenvironment generated for plastic cover. Coinciding this aspect with the reported for Hurd and Graves (1985) and Sawhney and Polowick (1985), indicating that high temperature increasing the rate growth. Although the quantity of light was higher inside greenhouses covered with plastic, the glass cover have a higher selectivity of the irradiation (Serrano, 1994; Papadopoulos and Hao, 1997), allowing to kept a homogeneous and high temperature with respect to plastic covers, explaining the higher rate growth showed in this greenhouses, to this respect Pearce et al. (1993a) explained that the rate growth of the tomato fruit is determined primarily by temperature and irradiation. Statistical analysis of the dry matter content of the tomatoes indicated that the season factor was very significant. Winter fruit had higher dry matter content with respect to autumn fruit (Table 2). The dry matter accumulation as a percentage in fruit showed a dramatic fall until 21 days of growing, mainly due to increasing in accumulated water (Fig. 3) that characterizes the process of cellular expansion (Cuartero et al., 1995); this fall was more marked in the autumn fruits. After growing period in days there was an increment of the dry matter content that was more notorious in the winter fruits and less important in the autumn fruits. In winter the dry matter content in the fruits reached its maximum value after to the 28 days of development, with values of 4.4%, while in the fruits harvested in the autumn season, the dry matter content was increased from 2.7 up to 4.3%. The dry matter content of the b ct 482
tomato in the mature green state ranged from of 4.3 to 4.6. This value is low as compared to that of Hobson and Davies (1981) who established an interval from 5 to 7%. However, it is necessary to consider that the fruit used in this study was harvested in the green mature when they have not synthesized all their components, in contrast with the work of the authors cited above, who values for ripe fruits. The distribution of quality of fruits in the production of both types of covered and study seasons are shown in the Figure 4. The proportion of fruits of high quality ('Premium') was high in both seasons and cover type that reflected the good handling practices applied by the company. In the autumn season the fruits of Premium quality were of 85% in both covers, and higher that those obtained in winter. In the winter season the fruits grown in plastic covered had higher percentage of 'Premium' quality with respect to that greenhouse with glass covered (8 vs. 7% respectively), suggering that the plastic cover generated an atmosphere more appropriate for the good development of the fruit and with less susceptibility to the defects. The autumn fruits grown in greenhouses covered with glass presented a highest rate growth than the fruit from any other treatment but they also have a smaller dry matter content. This could be the result of the high necessity of plant transpiration in an atmosphere of high temperature that accumulates more water in the fruit generating a smaller dry matter content. For the winter season the best atmosphere seems to be generate when it is covered with plastic, since that highest proportion of fruits of better quality was obtained under these conditions, mainly due to the lower temperature reached inside the greenhouse, and is well know that lower temperatures diminished the plant transpiration and therefore a better accumulation of dry matter, whereas the higher temperature reached inside the greenhouses covered with glass promoted more favourable conditions for the development of defects. ACKNOWLEDGEMENTS The authors thank to AGROS S.A. de C.V. Company for their technical support for the accomplishment of this work. Literature Cited Adams, S.R., Cockshull, K.E. and Cave, C.R.J. 21. Effect of temperature on the growth and development of tomato fruits. Annals of botany 88:869-877. Davies, J.N. and Hobson, G.E. 1981. The constituents of tomato fruit. The influence of enviroment, nutrition and genotype. Critical Reviews in Food Science Nutrition. 15(3):25-28. Cuartero, Z.J., Hernández-Muñoz, R and González, F.J. 1995. Estréses abióticos. In: Nuez, F. El cultivo del tomate. Ediciones Mundiprensa. 352-383. Dorais, M., Badrane, M., Gosellin, A., Hao, X. and Papadopoulos, A. 22. Greenhouse covering materials and supplemental lighting affect growth, yield, photosynthesis, and leaf carbohydrate synthesis of tomato plants. J. Amer. Soc. Hort. Sci. 127(5):819-824. Ho, L.C. 1996. Tomato. In: Amski, E. and Shaffer, A. Photoasimilate distribution in plants and crops. Source-sink relationships. Marcel Dekker, Inc. 3:79-727. Hurd, R.G. and Graves, C.J. 1985. Some effects of air and root temperatures on the yield and quality of glasshouse tomatoes. Journal of Horticultural Science 6: 359-371. Lopez, B.J., Tremblay, N., Voogt, W., Dubé, S. and Gosselin, A. 1996. Effect of varing sulphate concentration on growth, physiology and yield of the greenhouse tomato. Scientia Horticulturae. 67:27-217. Matallana, G.A. and Montero, C. 1995. Invernaderos: Diseño, construcción y climatización. Ediciones Mundiprensa. 29 p. Monselise, S.P., Varga, A. and Bruinsma, J. 1978. Growth analysis of the tomato fruit. Lycopersicon esculentum Mill. Annals of botany. 42:1245-1247. Noble, R. and Holder. 1989. Pot plant production under various greenhouse clading materials. J. Hort. Sci. 64:485-493. Papadopoulos, A.P. and Hao, X. 1997. Effects of the greenhouse covers on seedless cucumber growth, productivity and energy use. Scientia Hort. 68:113-123. Pearce, B.D., Grange, R.I. and Hardwick, K. 1993a. The Growth of young tomato fruit. I. Effects of temperatura and irradiance on fruit grown in controlled environments. Journal of Horticultural Science. 68(1):1-11. 483
Pearce, B.D., Grange, R.I. and Hardwick, K. 1993b. The Growth of young tomato fruit. I. Environmental influences on glasshouse crops grown in rookwool or nutrient film. Journal of Horticultural Science. 68(1):13-23. Sawhney, V.K. and Polowick, P.L. 1985. Fruit development in tomato: the role of temperature. Canadian Journal of Botany 63: 131-134. Serrano, Z. 1994. Construcción de invernaderos. Ediciones Mundi prensa. 445 p. Tables Table 1. Analysis of variance of coefficients calculated from a Gompertz Model. Cover Season a b c Plastic Autumn 266.7819 1.453495.56436 Glass 286.6937 1.515783.5499 Glass Autumn 223.3155 1.883214.79872 Glass 276.658 1.488131.59968 Crop season NS * * Cover NS * ** Season x Cover NS ** NS *, ** and *** significantly different to P.5,.1 y.1, respectively; NS non-significant. Table 2. Analysis of variance of the dry matter content (%) in tomato fruits grown in two greenhouse cover and two crop season. Cover Season Plastic Autumn 6.4894 3.59277 2.5652 3.4414 3.287 3.56843 4.27259 Winter 4.25459 3.5795 2.74522 4.63853 4.54317 4.7996 4.47938 Glass Autumn 7.266 2.9448 2.6275 2.66628 3.68418 3.86195 4.28999 Winter 7.2459 3.5795 3.17154 4.76231 4.76758 4.46523 4.57652 Crop Season * ** NS *** *** *** ** Cover *** ** NS NS NS NS NS Crop Season * Cover ** ** NS NS NS * NS *, ** and *** significantly different to P.5,.1 y.1, respectively; NS non-significant. 484
Figures J/s 14 12 1 8 6 4 2 Autumn 3 25 2 15 C J/s 14 12 1 8 6 4 2 Light Plastic Light Glass Temp Plastic Temp Glass Winter Fig. 1. Mean average daily temperatures and internal light of two greenhouse covers and two crop seasons. 3 25 2 15 C 3 Autumn Winter 25 2 ml 15 1 5 Plastic Gompertz Plastic Glass Gompertz Glass Plastic Gompertz Plastic Glass Gompertz Glass. Fig. 2. Growth curves of tomato plants cv. 716 grown in two greenhouse covers and two crop seasons and fitted to a Gompertz model. (Solid line was model fitted, the marks were experimental dates). 485
1 8 PlasticAutumn GlassAutumn PlasticWinter GlassWinter 6 % DM 4 2 Fig. 3. Dry matter content in tomato fruits grown in two greenhouse cover and two crop season. 1 Autumn Winter 8 Plastic Glass % total yield 6 4 2 Premium First class Nacional Premium First class Nacional Fig. 4. Distribution of tomato fruits quality cv. 716 grown in two greenhouse covers and two crop seasons. 486