George Daskas

Plant biostimulants may alter photosynthetic energy use and leaf structure, but their effects on complementary PSII energy partitioning in both cucumber leaves and fruits remain insufficiently characterized. Using plant material from a commercial greenhouse trial previously reported for agronomic outcomes, we evaluated a combined CropBioLife^®, KeyPlex 120^®, and Key Eco Oil^® application protocol relative to conventional management. Chlorophyll Content Index (CCI), chlorophyll fluorescence imaging, and leaf anatomical traits were assessed. Under low light (LL; 455 μmol photons m⁻² s⁻¹), the combined-treatment greenhouse showed higher ΦPSII than the conventional-control greenhouse by 22% in fruits and 50% in leaves; fruit ΦNPQ was 17% higher, whereas ΦNO was 12% lower in fruits and 26% lower in leaves. Under high light (HL; 973 μmol photons m⁻² s⁻¹), differences in ΦPSII were smaller, while leaf ΦNO remained 17% lower. CCI was 38% higher in fruits and 52% higher in leaves. In leaves, spongy parenchyma thickness increased from 110 ± 3.4 to 135 ± 4.1 μm, palisade parenchyma thickness from 75 ± 2.1 to 78 ± 1.8 μm, total leaf thickness from 230 ± 4.6 to 245 ± 5.2 μm, and intercellular air-space area from 420 ± 18 to 610 ± 22 μm². The parallel physiological and anatomical differences are consistent with a possible functional association, but gas exchange, mesophyll conductance, ROS, and water-use efficiency were not measured in the present dataset. Because the two management regimes occupied separate, non-replicated greenhouses and received different crop-protection inputs, the findings should be interpreted as treatment-associated differences rather than causal effects attributable to individual products.

The agricultural industry faces increasing environmental degradation due to the intensive use of conventional chemical fertilizers, leading to water pollution and alterations in soil composition. In addition, root-knot and cyst nematodes are major constraints to cucumber production, causing severe root damage and yield losses worldwide, underscoring the need for sustainable alternatives to conventional fertilization and pest management. Under greenhouse conditions, a four-month cultivation trial evaluated vegetable oil-, micronutrient-, and activated flavonoid-based biostimulants, applying Key Eco Oil^® (Miami, USA) via soil drench (every 15 days) combined with foliar sprays of CropBioLife^® (Victoria, Australia) and KeyPlex 120^® (Miami, USA) (every 7 days). Results showed reduced parasitic nematodes by 66% in soil and decreased gall formation by 41% in roots. Chlorophyll fluorescence and infrared gas analysis revealed higher oxygen-evolving complex efficiency (38%), increased PSII electron transport, improved the fluorescence decrease ratio, also known as the vitality index (Rfd), and higher CO₂ assimilation compared to conventional treatments. Processed cucumbers showed higher sugar and nearly double ascorbic acid content, with improved flesh consistency and color. Therefore, the application of these bioactive products significantly reduced nematode infestation while enhancing plant growth and physiological performance, underscoring their potential as sustainable tools for crop cultivation and protection. These results provide evidence that sustainable bioactive biostimulants improve plant resilience, productivity, and nutritional quality, offering also an environmentally sound approach to pest management.

Biostimulants contribute to the physiological growth of plants by enhancing the quality characteristics of fruit without harming the environment. In addition, biostimulants applied to plants strengthen nutritional efficiency, abiotic stress tolerance, and fruit biochemical traits. We investigated the effectiveness of specific organic biostimulants. Five treatments were tested: (1) control (H₂O, no biostimulants); (2) Magnablue + Keyplex 350 (Mgl + Kpl350); (3) Cropobiolife + Keyplex 120 (Cpl + Kpl120); (4) Keyplex 120 (Kpl120); and (5) Magnablue + Cropobiolife + Keyplex 120 (Mgl + Cpl + Kpl120) on the mineral uptake and physiology in black chokeberry (Aronia) plants, as well as the quality of their berries. The different treatments were applied to three-year-old chokeberry plants, and the experimental process in the field lasted from May to September 2022 until the harvest of ripe fruits. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) revealed that the fifth treatment significantly increased concentrations of P, Ca, and K. Additionally, the fifth treatment enhanced photochemical efficiency (Fv/Fm), water-splitting efficiency (Fv/Fo) in PSII, and the performance index (PI) of both PSI and PSII in chokeberry leaves. Improvements in photosynthesis, such as CO₂ assimilation (A), transpiration (E), and water-use efficiency (A/E), were also noted under biostimulant applications. Upon harvesting the ripe fruits, part of them was placed at room temperature at 25 °C, while the rest were stored at 4 °C, RH 90% for 7 days. The cultivation with biostimulants had beneficial effects on the maintenance of flesh consistency, ascorbic acid concentration, and weight of berries at 4 and 25 °C, especially in the 5th treatment. Moreover, the total antioxidant capacity, anthocyanin concentration, and total phenols of the berries were notably higher in the third and fifth treatments compared to the control. These data suggest that selecting appropriate biostimulants can enhance plant yield and fruit quality by potentially activating secondary metabolite pathways.