Mitigation of salt stress in lettuce by a biostimulant that protects the root absorption zone and improves biochemical responses

Abstract

Horticultural crops constantly face abiotic stress factors such as salinity, which have intensified in recent years due to accelerated climate change, significantly affecting their yields and profitability. Under these conditions, it has become necessary to implement effective and sustainable solutions to guarantee agricultural productivity and food security. The influence of BALOX®, a biostimulant of plant origin, was tested on the responses to salinity of Lactuca sativa L. var. longifolia plants exposed to salt concentrations up to 150 mM NaCl, evaluating different biometric and biochemical properties after 25 days of treatment. Control plants were cultivated under the same conditions but without the biostimulant treatment. An in situ analysis of root characteristics using a non-destructive, real-time method was also performed. The salt stress treatments inhibited plant growth, reduced chlorophyll and carotenoid contents, and increased the concentrations of Na+ and Cl- in roots and leaves while reducing those of Ca2+. BALOX® application had a positive effect because it stimulated plant growth and the level of Ca2+ and photosynthetic pigments. In addition, it reduced the content of Na+ and Cl- in the presence and the absence of salt. The biostimulant also reduced the salt-induced accumulation of stress biomarkers, such as proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2). Therefore, BALOX® appears to significantly reduce osmotic, ionic and oxidative stress levels in salt-treated plants. Furthermore, the analysis of the salt treatments’ and the biostimulant’s direct effects on roots indicated that BALOX®’s primary mechanism of action probably involves improving plant nutrition, even under severe salt stress conditions, by protecting and stimulating the root absorption zone.

Agroindustrial By-Products as a Source of Biostimulants Enhancing Responses to Abiotic Stress of Horticultural Crops

“…This product, applied to the root system of Lactuca sativa plants by irrigation, improves tolerance against salt stress by decreasing oxidative stress, promoting growth and improving photosynthesis and primary metabolism. As shown in Figure 3 , the enhanced salt tolerance is due, at least in part, to the protection of the root absorption zone from the damage caused under high salinity conditions, favouring the emission of finer roots primarily responsible for nutrient uptake [ 89 ].…”

“…Chemical or enzymatic hydrolysis of proteins produces amino acids and peptide mixtures from agroindustrial by-products, which can be of vegetable origin (crop by-products: seeds, husks, biomass and fruits) [ 34 , 57 , 84 , 86 , 89 , 90 ] or derived from animals, e.g., blood, feathers, viscera, bones, skins and other waste products [ 35 , 76 , 81 , 91 , 92 , 93 , 94 ]. These mixtures contain bioactive compounds that function as plant biostimulants, improving growth and enhancing abiotic stress tolerance.…”

“… Lactuca sativa roots under salt stress conditions (50 mM NaCl). ( a ) Plants treated with BALOX ® , a biostimulant based on plant protein hydrolysates and ( b ) control, non-treated plants; see [ 89 ]. …”

“…Chemical or enzymatic hydrolysis of proteins produces amino acids and peptide mixtures from agroindustrial by-products, which can be of vegetable origin (crop byproducts: seeds, husks, biomass and fruits) [34,57,84,86,89,90] or derived from animals,…”

“…[45,57,82] Lettuce (Lactuca sativa L.) Promotes growth and protects and stimulates the absorption zone of the roots. [89] Graminaceae Salt stress Lettuce (Lactuca sativa L.) Promotes growth, increasing the fresh weight of shoots. [78] Pumpkin seeds Salt stress Common bean (Phaseolus vulgaris L.) Enhances the nutritional status.…”