Abstract
Priming has been used to improve the performance of germination at the field, and potassium nitrate (KNO3) is a promising compound for this purpose. The nitrate (NO3) could be absorbed, being used in the metabolism of the embryo, through the enzyme nitrate reductase (NR). Besides, the priming could also activate the response of the antioxidant system, becoming the primed seeds more prepared for possible stresses. Thus, the aim of this study was to evaluate the metabolic effect of nitrate in tomato seed germination by the quantification of NR activity, and also evaluate the activity of some antioxidant enzymes as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Tomato seeds were primed using solutions of polyethylene glycol (PEG 6000) -1,1MPa, 50 mM KNO3 and PEG+KNO3. The variables analyzed were germination (germinability, mean germination time, mean germination rate, coefficient of variation of the germination time, uncertainty and synchrony) nitrogen, total proteins and enzymes. The germination data were analyzed using an ANOVA, comparing the averages by Scott-Knott test (P < 0.05). To analyze the nitrogen, protein and enzymatic activities, we used a Kruskal-Wallis test (P < 0.05). The results show an increase in the NR activity, as well as in the antioxidant enzymes. The germination time (t) and germination rate (v) primed in KNO3 had a better performance compared to the other treatments. In conclusion, the observed benefits in tomato seeds primed with KNO3 were related to the activity of the enzyme nitrate reductase in the production of nitrite/nitric oxide, which acted promoting a faster germination.
Highlights
The most sensitive stages, for many crop species submitted to the stress conditions, are seed germination and early seedling growth (Rahimi, 2013)
The results show an increase in the nitrate reductase (NR) activity, as well as in the antioxidant enzymes
The observed benefits in tomato seeds primed with KNO3 were related to the activity of the enzyme nitrate reductase in the production of nitrite/nitric oxide, which acted promoting a faster germination
Summary
The most sensitive stages, for many crop species submitted to the stress conditions, are seed germination and early seedling growth (Rahimi, 2013). The seed germination performance indicators (germinability, germination time, germination rate and synchronization index) are very important for successful crop production. Seed priming has been used to accelerate the germination, uniform seedling emergence and improve a germination performance under the temperature or drought stresses (Janmohammadi, Dezfuli, & Sharifzadeh, 2008; Jahangir, Amjad, Afzal, Iqbal, & Nawaz, 2009). Seed priming with nitrate solutions resulted in better seed quality and stand establishment in maize field grown (Hanegave, Hunje, Nadaf, Biradarpatil, & Uppar, 2011). Nitrate solutions helped in shorting a time required for spread of germination in tomato (Farooq, Basra, Saleem, Nafees, & Chisthi, 2005)
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