Germinação, desenvolvimento e produção do tomateiro industrial, sob estresse salino.

Abstract

The cultivar IPA 6 occupies most of the planting cultivated with industrial tomato in Brazil. Despite being a crop very much cultivated in semi-arid areas, subjected to salinity problems, information on its tolerance to salinity are still scarce for different stages of the crop cycle of this cultivar. In that sense, an experiment was conducted to study the effects of salinity and proportion of Na, Ca and Mg in the irrigation water on the tomato (Lycopersicon esculentum Mill). In the first phase, the effects of 5 salinity levels, ECw (1, 2, 3, 4 and 5 dS.m"1) and three proportions of sodium, 1, 4 and 7, maintaining the proportions of calcium and magnesium 1,0 and 0,5 respectively in the irrigation water, on germination, vigor and formation of the seedling of the tomato, under greenhouse conditions were evaluated using, trays of rigid polystyrene of 128 cells and industrial substrate for production of vegetable seedlings. A completely randomized design was used in 5x3 factorial scheme, with 4 repetitions. In the second phase, the effects of 5 salinity levels (1, 2, 3, 4 and 5 dS.m'1) and two proportions of Na:Ca:Mg (Pi = 1:1:0,5 and P2 = 7:1:0,5) in the irrigation water, were studied in the vegetative development up to beginning of the flowering stage and fructification, maturation and yield (stage II), using seedlings produced with the same salinity levels and proportion, produced in the phase I, conduced in rizotrons, protected by plastic covering. A completely randomized design was used in a 5x2 factorial scheme, with 3 repetitions, From the results obtained, it was concluded that in the final counting, that is, 14 days after sowing, the percentage of germination did not suffer effect of the treatments, but the index of emergence speed decrease with the increase of salinity and sodium. For the appraised growth parameters, it could be concluded that the vegetative growth of the aerial parts, in terms of phytomass, length and area, decrease with a increment of salinity, in all the studied phases. The same behavior was observed with the increase of Na in the irrigation water, except for length of the stem at 7 and 71 days after the sowing, dry phytomass of the aerial parts and total leaf area, at 71 days after sowing, showed increase with the increase of sodium. The growth of the root system, in terms of phytomass, decrease with the increase of salinity and of sodium, in all phenological stages. In terms of root length, the increase in salinity provoked decrease of this variable for the evaluations at 7 and 14 days, and increased at the 21 days after sowing. The increment of the proportion provoked growth of root length from 7 to 21, and decreased the growth from 1 to 7 days after sowing. Regarding the production components, the increment of salinity affected negatively the mean weight of fruits, the phytomass of seeds per fruit, the fresh phytomass of produced fruits and the index of crop speed, and caused increment in the brix and in the acidity. The increase of sodium provoked decrease in number of good fruits, of the fresh and dry phytomass of fruits and in the index of yield harvest, causing delay in fructification or the maturation. In general, the tomato, cv. IPA 6, has higher tolerance to salinity than others crops reported in the literature, since the relative decrease in the phytomass of fruits were smaller than the ones found for other crops.