Abstract
The salinity in irrigation water is one of the most important causes to decline cultivated plants yield. The H2O2 application has shown efficiency as a stimulator and activator for antioxidative defense system in plants submitted to biotic and abiotic stresses. The objective of this study was to evaluate methods for hydrogen peroxide application as a strategy to minimize the effects of saline stress on melon plants. The experiment was designed in complete randomized blocks and set in 2 × 4 factorial scheme, consisting two levels for irrigation water salinity (S1 = 0.3 and S2 = 2.0 dS m-1) and four methods for hydrogen peroxide application (15 mM), (T1 = no peroxide application, T2= imbibition of seeds, T3 = at sowing, T4 = Foliar spraying), with five repetitions. It was evaluated the following variables at 58 days after transplanting: plant height, stem diameter, number of leaves, number of flowers, shoot dry mass, root dry mass and total dry mass. The results showed that salinity affected the growth, biomass accumulation and plant quality severely, with the highest losses promoted by the electrical conductivity of 2.0 dS m-1.
Highlights
The treatments were arranged in a randomized block design, and set in a 2 × 4 factorial scheme, corresponding to two irrigation water salinity levels (S1 = 0.3 and S2 = 2.0 dS m-1) and four methods of hydrogen peroxide application (15 mM), T1 = no peroxide application; T2 = imbibition of seeds; T3 = at sowing; T4 = Foliar spraying, with five repetitions containing two plants placed in perforated rectangular plastic pots, to aid in the flow of excess water
The growth for plant height, stem diameter, number of leaves and flowers got the influence of water salinity and hydrogen peroxide applications, which plants submitted to the salinity of 2.0 dS m-1 (Table 2) presented severe reductions
It was noticed that plant height, stem diameter and number of leaves hydrogen peroxide, regardless of the application method, did not promote attenuating salinity effects when compared to the control, showing that hydrogen peroxide did not mitigate the effects promoted by saline stress (Table 2)
Summary
The melon cultivation (Cucumis melo L.) has increased significantly in the last years in Brazil, representing one of the tropical fruits with greater commercial interest, and its major producers are Rio Grande do Norte and Ceará states (Faria, Lima, Ciqueira, Rezende, & Gomes, 2015),which guarantee to Brazil the highest global production of melon.Despite this plant has a wide adaptability to the Northeast region, its cultivation in the world's semi-arid areas presents a risk, mainly due to the scarcity of water resources related to the low rainfall intensity, besides the irregularity of the rains and high evaporation, which require the use of poor quality water, usually rich in salts, mainly sodium (Medeiros, Barbosa, Medeiros, Rocha, & Silva, 2010).The search for alternatives that attenuate the effect of salinity stress on plants is increasing, aiming to promote the acclimatization of plants to survive in adverse conditions. The melon cultivation (Cucumis melo L.) has increased significantly in the last years in Brazil, representing one of the tropical fruits with greater commercial interest, and its major producers are Rio Grande do Norte and Ceará states (Faria, Lima, Ciqueira, Rezende, & Gomes, 2015),which guarantee to Brazil the highest global production of melon Despite this plant has a wide adaptability to the Northeast region, its cultivation in the world's semi-arid areas presents a risk, mainly due to the scarcity of water resources related to the low rainfall intensity, besides the irregularity of the rains and high evaporation, which require the use of poor quality water, usually rich in salts, mainly sodium (Medeiros, Barbosa, Medeiros, Rocha, & Silva, 2010). It happens because hydrogen peroxide boosts the intracellular region to activate plant defense responses to stress caused by excess salts, promoting cross-tolerance (Mittler, 2002)
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