Salinity is a limiting factor that can affect plant growth and cause significant losses in agricultural productivity. This study provides an insight about the viability of partial root-zone irrigation (PRI) system with saline water supported by a biochemical approach involving antioxidant responses. Six different irrigation methods using low and high salt concentrations (S1-0.5 and S2-5.0 dS m) were applied, with or without PRSI, so that one side of the root-zone was submitted to saline water while the other side was low salinity water irrigated. The results revealed different responses according to the treatments and the PRSI system applied. For the treatments T1, T2 and T3, the PRSI was not applied, while T4, T5 and T6 treatments were applied with PRSI system. Lipid peroxidation, proline content, and activities of SOD, CAT, APX, GR and GSH in tomato plants subjected to PRSI system were analyzed. Plant growth was not affected by the salt concentrations; however, plants submitted to high salt concentrations showed high MDA content and Na accumulation when compared to the control plants. Plants submitted to treatments T4, T5 and T6 with PRSI system exhibited lower MDA compared to the control plants (T1). Proline content and activities of SOD, CAT, APX, GR and GSH content were maintained in all treatments and tissues analyzed, with only exception for APX in fruits and GSH content, in roots. The overall results showed that PRSI system could be an applicable technique for saline water supply on irrigation since plants did not show to be vulnerable to salt stress, supported by a biochemical approach involving antioxidant responses.

Seed germination and seedling growth are the stages most sensitive to salt stress, which can induce ion-specific effects and oxidative stress. Although silicon (Si) has been known to improve plant defense systems against stressful-conditions, little is known about seed priming with Si and mechanisms of Si-mediated alleviation of salt stress in seedlings. To further the modulation of salt-stress responses and their relation with Si, seed priming with calcium silicate (0, 0.05 and 0.1 mM Ca 2 SiO 4) was used in lettuce seeds to improve seed germination and tolerance on subsequent salt-stress exposure (0 and 50 mM NaCl). The effect of Si-priming was assessed on germination, germination rate index and mean germination time and survival of seedlings in salt-stressful conditions supported by biochemical approach involving antioxidant responses. Overall results indicated that Si plays a role in alleviating the negative effects of salt stress by improving germination performance and displayed increased SOD, CAT and GR activities and reduced malondialdehyde and H 2 O 2 contents. Thus, our findings demonstrate that seed-priming with Si is an efficient management technique that can be used to alleviate deleterious effects of salt-stressful on germination of lettuce seeds and enhance salt tolerance of seedlings due the increased activity of ROS-scavenging enzymes.

This research aimed to evaluate the yield and quality of tomato plants under different managements of salt stress by adopting the partial root-zone saline irrigation (PRSI) system. The experiment was conducted in a greenhouse at the Universidade Federal Rural do SemiÁrido (UFERSA), Mossoró, Rio Grande do Norte (RN), Brazil. The experimental design was completely randomized, with six treatments and four replicates, totaling 24 plots. The treatments consisted of six different irrigation management regimes using low and high saline water (S1–0.5 and S2–5.0 dS·m−1), applied with or without PRSI, such that one side of the root-zone was submitted to saline water whilst the other side was water low salinity irrigated. For treatments T1 (control), T2 (S2 water), and T3 (alternate irrigation system between S1 and S2, with a cycling period of 15 d for each one), the PRSI was not applied; T4 (irrigation with S1 and S2, adopting the PRSI system from phase II to phase IV), T5 (irrigation with S1 and S2 in phase II, alternating in phase III; in phase III the inversion of the remaining water was made until the end of phase IV), and T6 (irrigation with S1 and S2, adopting the PRSI system in phase II, with the water switched between low and high saline water every 15 days, remaining until the end of phase IV) treatments were under the PRSI. The number of fruit per plant, fruit weight, fruit longitudinal and transverse diameter, pulp firmness, soluble solids content, titratable acidity, pH, vitamin C, color relation (a*/b*), lycopene, and β-carotene were determined as parameters for the fruit yield and quality evaluation. Our findings reinforce the importance of the use of PRSI systems followed by irrigation managements without loss of product quality, such as demonstrated by T4 and T5 water managements.

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