Abstract
Plant-derived protein hydrolysates (PHs) are gaining prominence as biostimulants due to their potential to improve yield and nutritional quality even under suboptimal nutrient regimens. In this study, we investigated the effects of foliar application of a legume-derived PH (0 or 4 mL L−1) on greenhouse baby spinach (Spinacia oleracea L.) under four nitrogen (N) fertilization levels (0, 15, 30, or 45 kg ha−1) by evaluating morphological and colorimetric parameters, mineral composition, carbohydrates, proteins, and amino acids. The fresh yield in untreated and biostimulant-treated spinach plants increased in response to an increase in N fertilization from 1 up to 30 kg ha−1, reaching a plateau thereafter indicating the luxury consumption of N at 45 kg ha−1. Increasing N fertilization rate, independently of PH, lead to a significant increase of all amino acids with the exception of alanine, GABA, leucine, lysine, methionine, and ornithine but decreased the polyphenols content. Interestingly, the fresh yield at 0 and 15 kg ha−1 was clearly greater in PH-treated plants compared to untreated plants by 33.3% and 24.9%, respectively. This was associated with the presence in of amino acids and small peptides PH ‘Trainer®’, which act as signaling molecules eliciting auxin- and/or gibberellin-like activities on both leaves and roots and thus inducing a “nutrient acquisition response” that enhances nutrients acquisition and assimilation (high P, Ca, and Mg accumulation) as well as an increase in the photochemical efficiency and activity of photosystem II (higher SPAD index). Foliar applications of the commercial PH decreased the polyphenols content, but on the other hand strongly increased total amino acid content (+45%, +82%, and +59% at 0, 15, and 30 kg ha−1, respectively) but not at a 45-kg ha−1-rate. Overall, the use of PH could represent a sustainable tool for boosting yield and nitrogen use efficiency and coping with soil fertility problems under low input regimens.
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Claims 10
Claim · model-written summary
Spinach fresh yield increased with nitrogen up to 30 kg ha−1 then plateaued.
- Taxon
- spinach plants
Spinacia oleraceae0 - Treatment
- increase in N fertilizatione0
- Outcome
- fresh yielde0
- Direction
- increasede0
- Qualifier
- from 1 up to 30 kg ha−1e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“fresh yield in untreated and biostimulant-treated spinach plants increased in response to an increase in N fertilization from 1 up to 30 kg ha−1, reaching a plateau thereafter”
Claim · model-written summary
Increasing nitrogen significantly raised most amino acids.
Not reportedTaxonComparator
Verbatim
e0“Increasing N fertilization rate, independently of PH, lead to a significant increase of all amino acids with the exception of alanine, GABA, leucine, lysine, methionine, and ornithine”
Claim · model-written summary
Increasing nitrogen reduced polyphenols content.
Not reportedTaxonComparator
Verbatim
e0“Increasing N fertilization rate, independently of PH, lead to a significant increase of all amino acids with the exception of alanine, GABA, leucine, lysine, methionine, and ornithine but decreased the polyphenols content”
Claim · model-written summary
PH raised fresh yield by 33.3% at zero nitrogen.
- Treatment
- PH-treated plantse0
- Outcome
- fresh yielde0
- Direction
- greatere0
- Value
- 33.3%e0
- Comparator
- untreated plantse0
Not reportedTaxon
Verbatim
e0“fresh yield at 0 and 15 kg ha−1 was clearly greater in PH-treated plants compared to untreated plants by 33.3% and 24.9%, respectively”
Claim · model-written summary
PH raised fresh yield by 24.9% at 15 kg ha−1 nitrogen.
- Treatment
- PH-treated plantse0
- Outcome
- fresh yielde0
- Direction
- greatere0
- Value
- 24.9%e0
- Comparator
- untreated plantse0
Not reportedTaxon
Verbatim
e0“fresh yield at 0 and 15 kg ha−1 was clearly greater in PH-treated plants compared to untreated plants by 33.3% and 24.9%, respectively”
Claim · model-written summary
PH decreased polyphenols content.
Not reportedTaxonComparator
Verbatim
e0“Foliar applications of the commercial PH decreased the polyphenols content”
Claim · model-written summary
PH raised total amino acids by 45% at zero nitrogen.
Not reportedTaxonComparator
Verbatim
e0“Foliar applications of the commercial PH decreased the polyphenols content, but on the other hand strongly increased total amino acid content (+45%, +82%, and +59% at 0, 15, and 30 kg ha−1, respectively)”
Claim · model-written summary
PH raised total amino acids by 82% at 15 kg ha−1 nitrogen.
Not reportedTaxonComparator
Verbatim
e0“Foliar applications of the commercial PH decreased the polyphenols content, but on the other hand strongly increased total amino acid content (+45%, +82%, and +59% at 0, 15, and 30 kg ha−1, respectively)”
Claim · model-written summary
PH raised total amino acids by 59% at 30 kg ha−1 nitrogen.
Not reportedTaxonComparator
Verbatim
e0“Foliar applications of the commercial PH decreased the polyphenols content, but on the other hand strongly increased total amino acid content (+45%, +82%, and +59% at 0, 15, and 30 kg ha−1, respectively)”
Claim · model-written summary
PH did not raise total amino acids at 45 kg ha−1.
Not reportedTaxonComparatorDirection
Verbatim
e0“Foliar applications of the commercial PH decreased the polyphenols content, but on the other hand strongly increased total amino acid content (+45%, +82%, and +59% at 0, 15, and 30 kg ha−1, respectively) but not at a 45-kg ha−1-rate”
The same questions in other papers
fertilization · yield · Spinacia oleracea (spinach)Results differ
67 papers in the same direction as this paper · 9 in the opposite direction · 2 reporting no difference from an alternative
- no effect
- no effect
- no effect
75 papers more in this group
See all 79 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.