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Biostimulants in Agriculture

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Front. Plant Sci. | doi: 10.3389/fpls.2018.01870

Effects of two doses of organic extract-based biostimulant on greenhouse lettuce grown under increasing NaCl concentrations

  • 1University of Milan, Italy
  • 2Institute of Life Science, Sant'Anna School of Advanced Studies, Italy

The enhancement of plant tolerance toward abiotic stresses is increasingly being supported by the application of biostimulants. Salinity represents a serious problem in the Mediterranean region. To verify the effects deriving from the application of biostimulants, trials on Romaine lettuce plants under salt exposure were performed, in greenhouse. Plants were subjected to three NaCl solutions with 0.8, 1.3, and 1.8 dS/m of electrical conductivity. The volume of the solution was 200 mL/plant and delivered every 3 days. Biostimulant treatments started after crop establishment and were: control (water) and two doses (0.1 or 0.2 mL/plant) of the commercial biostimulant Retrosal® (Valagro S.p.A), containing carboxylic acids, magnesium, zinc and calcium. Four Retrosal® treatments were applied, every seven days, directly to the substrate. Non-destructive analyses were conducted to assess the effects on leaf photosynthetic efficiency. At harvest, plants fresh weight and dry weight were determined, as well as the concentration of chlorophylls, carotenoids, total sugars, nitrate, proline, and abscisic acid. The biostimulant tested increased significantly the fresh weight of lettuce (+65% in the highest dose) compared to controls. Results indicate that treatments positively affected the chlorophyll content measured in vivo (+45% in the highest dose) and that a general positive effect was observable on net photosynthesis rate. Retrosal® seems to improve the gas exchanges under our experimental conditions. The total sugars levels were not affected by treatments. Biostimulant allowed maintaining nitrate concentration similar to the untreated and unstressed controls. The increasing levels of water salinity caused a raise in proline concentration in control plants (+85%); biostimulant treatments at 0.2 mL/plant dose kept lower the proline levels. All plants treated with the biostimulant showed lower value of ABA (-34%) compared to controls. Results revealed that Retrosal® is able to stimulate plant growth independently from the salinity exposure. However, treated plants reached faster the commercial maturity stage. The fresh biomass of control at the end of experiment, after 30 days, ranged from 15 to 42 g/head, while in biostimulant treated plants ranged from 45 to 94 g/head. The product applied at maximum dose seems to be the most effective in our experimental conditions.

Keywords: Salinity, Biochemical analyses, Non-destructive measurements, abiotic stress, Lactuca sativa L., biostimulant

Received: 31 May 2018; Accepted: 04 Dec 2018.

Edited by:

Youssef Rouphael, University of Naples Federico II, Italy

Reviewed by:

FRANCISCO PEREZ-ALFOCEA, Spanish National Research Council (CSIC), Spain
Marios C. Kyriacou, Department of Vegetable Crops, Agricultural Research Institute, Cyprus  

Copyright: © 2018 Bulgari, Trivellini and Ferrante. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Antonio Ferrante, University of Milan, Milan, Italy,