Effects of the ionic imbalance in the fertigation solution on growth, proline content and nitrate reductase activity in muskmelon seedlings

J. Olave, M. Guzman, A. Sanchez and C. Santander

Net Journal of Agricultural Science
Published: November 30 2018
Volume 6, Issue 4
Pages 63-69
DOl: https://doi.org/10.30918/NJAS.64.18.031

Abstract

The aim of this research was to evaluate the effects of ionic imbalance of fertigation solution in muskmelon (Cucumis melo) seedlings on growth, proline content and nitrate reductase activity (NRA). ‘Galia’ melon seeds were primed with 8 g•L^-1 of N different N-form fertilizers (NH₄NO₃, KNO₃ or NH₄NO₃+KNO₃), or non-primed (Control). These seeds were germinated and grown in perlite inside a passive greenhouse nursery. The water quality of “place Pintados region Tarapacá - Chile” was reproduced (EC: 2.6 dS m^-1, pH: 7.3; Na⁺: 12.2 meq L^-1, Cl^-: 18.12 meq L^-1, SAR_adj: 10.4). Four fertigation solutions were prepared with this water, maintaining a K⁺/(Ca²⁺ + Mg²⁺) ratio of 0.4 and pH between 6.1 and 6.6, but modifying EC (3.0; 4.1; 5.1; 6.2), SAR_adj (10.4; 9.2; 8.1; 7.0) and NO₃^-/Cl^- ratio (0.47; 0.73; 0.86; 1.25). The ionic ratio in fertigation solutions was modified during germination and seedling growth, which led to an increase of NO₃^- from 8.6 to 22.8 meq L^-1. Seedlings fertigated with 5.1 dS m^-1 (SAR_adj: 8.1) nutrient solution showed the highest plant height, leaf number and leaf area, but there was no significant effect on fresh and dry biomass. Proline content and NRA showed a high correlation with NO₃^- concentration. The lowest proline content was obtained at 12 meq L^-1 NO₃^- in the fertigation solution, indicating the lowest stress level and the highest efficiency in nitrogen absorption. Moreover, proline levels decreased before seedlings were planted. This different behaviour between endogenous and induced NRA may be useful to optimize NO₃^- supply and management in the nursery.

Keywords: Nutrient solution, salt stress, proline content, nitrate reductase activity.

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