The aim of the present study was to evaluate the effects of three biostimulant products
(Nomoren (N), Twin Antistress (TW), x-Stress (XS) and control treatment (C: no biostimulants added))
on the nutritional value, chemical composition and bioactive properties of greenhouse tomato fruit
grown under full (W+: 100% of field capacity) and deficit irrigation (W–: 70% of field capacity)
conditions. Fat content was the highest for the fully irrigated plants that received no biostimulants
(CW+), while proteins and carbohydrates and energetic value were the highest in the XSW+ treatment.
The content of the main detected sugars (fructose, glucose and trehalose) varied depending on the
irrigation and biostimulant treatment. The highest amounts of individual and total organic acids and
tocopherols were recorded in fully irrigated plants treated with Twin Antistress (TW), whereas the
lowest overall values were observed under deficit irrigation for plants that received the XS treatment.
The most abundant fatty acids were palmitic (27.5–36.0%) and linoleic acid (27.4–35.4%), followed by
oleic (9.2–21.2%), linolenic (5.4–13.1%) and stearic acid (5.3–6.8%). Moreover, the highest values of
-carotene and lycopene were recorded for the CW- and NW+ treatments, respectively. The TWW+
showed the highest antioxidant activity for both assays tested (TBARS and OxHLIA). Most of the
tested extracts showed lower antibacterial activity against the tested bacteria compared to the positive
controls. On the other hand, CW+, XSW+ and XSW- treatments showed higher antifungal activity
(MIC values) than positive controls. In conclusion, each biostimulant product had a different effect on
the determined characteristics depending on the level of irrigation. Therefore, more research is needed
to better identify the mechanisms of action and the physiological processes, after which the tested
biostimulants may be used to standardize the application of such products in tomato cultivation.
This research has been co-financed by the European Regional Development Fund of the
European Union and Greek national funds through the Operational Program Competitiveness,
Entrepreneurship and Innovation, under the call RESEARCH—CREATE—INNOVATE (project code:
T2EDK-05281). The authors are also grateful to the Foundation for Science and Technology (FCT,
Portugal) for the financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020),
and national funding by FCT, P.I., through the institutional scientific employment program contract
for A.F. and L.B.’s contracts.
