Abstract
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.
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Claims 14
Claim · model-written summary
Biostimulant increased lettuce fresh weight, reaching 65% at the highest dose.
- Taxon
- lettuce
Lactuca sativae1 - Treatment
- biostimulante1
- Outcome
- fresh weighte1
- Direction
- increasede1
- Value
- +65%e1
- Qualifier
- highest dosee1
- Comparator
- controlse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“The biostimulant tested increased significantly the fresh weight of lettuce (+65% in the highest dose) compared to controls.”
Claim · model-written summary
Biostimulant raised in vivo chlorophyll content by 45% at the highest dose.
- Taxon
- Romaine lettuce
Lactuca sativa var. longifoliae0 - Treatment
- treatmentse1
- Outcome
- chlorophyll contente1
- Direction
- positively affectede1
- Value
- +45%e1
- Qualifier
- highest dosee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“treatments positively affected the chlorophyll content measured in vivo (+45% in the highest dose)”
Claim · model-written summary
Biostimulant generally improved net photosynthesis rate.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- biostimulante2
- Outcome
- net photosynthesis ratee1
- Direction
- positive effecte1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“a general positive effect was observable on net photosynthesis rate”
e2“The biostimulant tested increased significantly the fresh weight of lettuce”
Claim · model-written summary
Retrosal appeared to improve gas exchange under the experimental conditions.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- Retrosal®e1
- Outcome
- gas exchangese1
- Direction
- improvee1
- Qualifier
- under our experimental conditionse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“Retrosal® seems to improve the gas exchanges under our experimental conditions.”
Claim · model-written summary
Treatments did not change total sugar levels.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- treatmentse1
- Outcome
- total sugars levelse1
- Direction
- not affectede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“The total sugars levels were not affected by treatments.”
Claim · model-written summary
Biostimulant maintained nitrate concentration near untreated, unstressed controls.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- Biostimulante1
- Outcome
- nitrate concentratione1
- Direction
- similare1
- Comparator
- untreated and unstressed controlse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“Biostimulant allowed maintaining nitrate concentration similar to the untreated and unstressed controls.”
Claim · model-written summary
Increasing water salinity raised control plant proline concentration by 85%.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- increasing levels of water salinitye1
- Outcome
- proline concentratione1
- Direction
- raisee1
- Value
- +85%e1
- Qualifier
- control plantse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“The increasing levels of water salinity caused a raise in proline concentration in control plants (+85%)”
Claim · model-written summary
The 0.2 mL/plant biostimulant dose kept proline levels lower.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- biostimulant treatments at 0.2 mL/plant dosee1
- Outcome
- proline levelse1
- Direction
- lowere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“biostimulant treatments at 0.2 mL/plant dose kept lower the proline levels.”
Claim · model-written summary
Biostimulant treated plants had ABA values 34% lower than controls.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- biostimulante1
- Outcome
- value of ABAe1
- Direction
- lowere1
- Value
- -34%e1
- Comparator
- controlse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“All plants treated with the biostimulant showed lower value of ABA (-34%) compared to controls.”
Claim · model-written summary
Retrosal stimulated growth independently of salinity exposure.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- Retrosal®e1
- Outcome
- plant growthe1
- Direction
- stimulatee1
- Qualifier
- independently from the salinity exposuree1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“Retrosal® is able to stimulate plant growth independently from the salinity exposure.”
Claim · model-written summary
Treated lettuce reached commercial maturity faster.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- treated plantse1
- Outcome
- commercial maturity stagee1
- Direction
- fastere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“treated plants reached faster the commercial maturity stage.”
Claim · model-written summary
Control plants had 15 to 42 g/head fresh biomass after 30 days.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Outcome
- fresh biomasse1
- Value
- 15 to 42 g/heade1
- Qualifier
- control at the end of experiment, after 30 dayse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“The fresh biomass of control at the end of experiment, after 30 days, ranged from 15 to 42 g/head”
Claim · model-written summary
Biostimulant treated plants had 45 to 94 g/head fresh biomass after 30 days.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Outcome
- biostimulant treated plantse1
- Value
- 45 to 94 g/heade1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“biostimulant treated plants ranged from 45 to 94 g/head.”
Claim · model-written summary
The maximum product dose appeared most effective under the experimental conditions.
- Taxon
- Romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- product applied at maximum dosee1
- Outcome
- most effectivee1
- Qualifier
- in our experimental conditionse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Romaine lettuce plants”
e1“The product applied at maximum dose seems to be the most effective in our experimental conditions.”
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