Phytohormones mediate physiological, morphological, and enzymatic responses and are important regulators of plant growth and development at different stages. Even though temperature is one of the most important abiotic stressors for plant development and production, a spike in the temperature may have disastrous repercussions for crop performance. Physiology and growth of two tomato genotypes ('Ahmar' and 'Roma') were studied in two growth chambers (25 and 45 °C) when gibberellic acid (GA3) was applied exogenously. After the 45 days of planting, tomato plants were sprayed with GA3 at concentrations of 25, 50, 75, and 100 mg L−1, whereas untreated plants were kept as control. Under both temperature conditions, shoot and root biomass was greatest in 'Roma' plants receiving 75 mg L−1 GA3, followed by 50 mg L−1 GA3. Maximum CO2 index, photosynthetic rate, transpiration rate, and greenness index were recorded in 'Roma' plants cultivated at 25 °C, demonstrating good effects of GA3 on tomato physiology. Likewise, GA3 enhanced the proline, nitrogen, phosphorus, and potassium levels in the leaves of both genotypes at both temperatures. Foliar-sprayed GA3 up to 100 mg L−1 alleviated the oxidative stress, as inferred from the lower concentrations of MDA and H2O2, and boosted the activities of superoxide dismutase, peroxidase, catalase. The difference between control and GA3-treated heat-stressed plants suggests that GA3 may have a function in mitigating heat stress. Overall, our findings indicate that 75 mg L−1 of GA3 is the optimal dosage to reduce heat stress in tomatoes and improve their morphological, physiological, and biochemical characteristics.

This study investigated the possibility of applying flat-pressed wood-polymer composites in conditions of high humidity. The experiment involved three variants of wood-polymer composite panels 16 mm thick, and 680 kg per m3 density. The wood particles were bonded with polyethylene. The share of polyethylene in the core layer was fixed at 50%, while in the face layers the content was varied (40%, 50%, or 60%). The following parameters were examined: modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), screw holding (SH), thickness swelling (TS), water absorption (WA), susceptibility to drilling and milling, wettability and surface free energy, and resistance to mold. The results were compared to particleboard glued with urea-formaldehyde resin. The wood-polymer composite had lower MOR and MOE values and similar IB and SH values. The panels indicated a remarkably higher water resistance (lower TS and WA values) with good surface wettability and high resistance to mold fungi. Additionally, the composites were easier to machine, e.g. drilling or milling, in comparison to standard particleboards.

In this study, wood plastic composites (WPC) made of poly(lactic acid) PLA and a bark-filler were manufactured. Two degrees of bark comminution (10–35 mesh and over 35 mesh) and varied content of bark (40, 50 and 60%) were investigated. The studied panels were compared with analogically manufactured HDPE boards. The manufacture of composites involved two stages: at first, WPC granules with the appropriate formulation were produced using the extruder (temperatures in individual extruder sections were 170–180 °C) and crushing using a hammer mill after cooling the extruded composite; secondly, the obtained granulate was used to produce boards with nominal dimensions of 300 × 300 × 2.5 mm3 by flat pressing in a mold, using a single daylight press at a temperature 200 °C. The study proved that comminuted bark can be applied as a filler in PLA composites. However, an increase in bark content decreased mechanical properties (MOR, MOE) and deteriorated humidity resistance (high TS and WA) of the panels. Along with the increase in bark content, an increase in the contact angle of the composite surfaces and a decrease in the total surface energy were noted. It was also found that PLA composites have higher strength parameters and lower moisture resistance compared to HDPE composites with the same bark content. Graphical abstract

Photosynthetic efficiency is significantly affected by both qualitative and quantitative changes during light exposure. The properties of light have a profound effect on electron transport and energy absorption in photochemical reactions. In addition, fluctuations in light intensity and variations in the spectrum can lead to a decrease in photosystem II efficiency. These features necessitate the use of a simple and suitable tool called chlorophyll a fluorescence to study photosynthetic reactions as a function of the aforementioned variables. This research implies that chlorophyll a fluorescence data can be used to determine precise light conditions that help photoautotrophic organisms optimally function.

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