PHYSIOLOGICAL QUALITY, FATTY ACIDS CONTENT AND RESPIRATION OF HUSK TOMATO SEEDS ARTIFICIALLY DETERIORATED

Abstract

During storage, seeds deteriorate due to mechanisms that reduce their germination rate, seedling growth rate and tolerance to adverse conditions. Seed deterioration can be measured by means of artificial aging tests (AA). In this research the artificial deterioration of husk tomato seeds (Physalis ixocarpa Brot.) var. ‘CHF1-Chapingo’ was evaluated, and the germination rate was correlated with fatty acids content and respiratory activity. In a first experiment, seeds were artificially aged by applying 55, 65 and 75 % of relative humidity (RH) at 45 and 50 °C, for 30 d and germination rate (G, %), seed vigor (radical emergence rate, RER) and fatty acids content (quantified by means of a gas chromatograph connected to a mass spectrometer) were evaluated. In a second experiment, seeds were aged by imposing 50, 55, 60, 65, 70, 75 and 80 % of RH at 50 °C for 30 d; G, RER and respiration rate (measured after 72 h of imbibition) were measured as response variables. It was found that linoleic acid was the most abundant fatty acid (87-93 % of the total content) in these seeds, and the increase of heat and relative humidity caused a significant reduction (P ≤ 0.05) in G and SER without affecting fatty acids content. Compared to untreated seeds (control), the combined effect of 50 °C and 65 % RH produced losses of 53 % in G and of 92 % in RER, in Experiment 1. The same treatment (50 °C and 65 % RH) induced losses of 21 % in G and of 78 % in RER when compared to responses at 50 °C and 50 % RH. The respiratory rate correlated with the losses in G (r = 0.88) and RER (r = 0.99), thus indicating that loss of physiological quality in deteriorated seeds can be attributed to the reduction in respiratory activity.