In the present study, we investigated changes in chlorophyll fluorescence, photosynthetic parameters and fruit yields, as well as fruit phytochemical accumulation of strawberry (Fragaria ananassa Duch.) that had been cultivated in a greenhouse under different combinations of light intensity and temperature. In plants grown with low light (LL) photosystem II chlorophyll fluorescence was found to increase as compared with those grown under high light (HL). When strawberry plants were grown with temperature higher than 5◦C in addition to LL, they showed decrease in non-photochemical quenching (NPQ), photochemical quenching (qP), as well as chlorophyll fluorescence decrease ratio (RFd) when compared with other combinations of light and temperature. Moreover, fruit yield of strawberry was closely correlated with chlorophyll fluorescence-related parameters such as NPQ, qP, and RFd, but not with the maximum efficiency of PS II (Fv/Fm). Although plant groups grown under different combinations of light and temperature showed almost comparable levels of photosynthesis rates (Pr) when irradiated with low-intensity light, they displayed clear differences when measured with higher irradiances. Plants grown under HL with temperature above 10◦C showed the highest Pr, in contrast to the plants grown under LL with temperature above 5◦C. When the stomatal conductance and the transpiration rate were measured, plants of each treatment showed clear differences even when analyzed with lower irradiances. We also found that fruit production during winter season was more strongly influenced by growth temperature than light intensity. We suggest that fruit productivity of strawberry is closely associated with chlorophyll fluorescence and photosynthesis-related parameters during cultivation under different regimes of temperature and light.

The objective of this study was to investigate characteristics of phenotypic parameters such as physiology, yield, and fruit quality responses of strawberry (Fragaria × ananassa Duch.) to various light intensity conditions (VLICs), and to determine the correlations among these phenotypic parameters. Strawberry plants were cultivated in a smart greenhouse separated into four areas, three of which were completely shaded by curtains from 20:00 until 10:00 (3 hS), 12:00 (5 hS), and 14:00 (7 hS), respectively. The fourth area was a non-shaded control treatment (0 hS). The ambient light intensities during the experimental period for the 0, 3, 5, and 7 hS treatments were 1,285, 1,139, 770, and 364 mol⋅m^–2, respectively. Strawberry plants grown under low light intensity conditions experienced decreases in photosynthetic rate, stomatal conductance, and sugar accumulation compared to the 0 hS. Petiole generation and fruit yield were also sharply decreased in proportion to the degree of decrease in light intensity. In contrast, photosynthetic pigment content was shown to increase under low light conditions. Organic acid contents (excluding acetic acid) and leaflet size did not change significantly under low light conditions compared to the 0 hS. Changes to light intensity are considered to induce changes to the phenotypic characteristics of strawberry plants to favor growth using the energy and carbon skeletons obtained through respiration and photosynthesis. In the 7 hS treatment, where light intensity was drastically reduced, NPQ, qP, and R_Fd values as chlorophyll a fluorescence parameters were significantly lowered, which could indicate their measurement as an important technique to check the stress response of plants grown in low light conditions.

This study aimed to investigate the combined effects of temperature and light conditions on tomato maturation. Tomato fruits that had completed volumetric growth at the mature green stage were harvested and matured in growth chambers composed of two temperature conditions (daytime–nighttime: 30–20 °C or 20–15 °C) and two light conditions (0 µmol·m⁻²·s⁻¹ or 400 µmol·m⁻²·s⁻¹), which were set for 12 h each day and night. Our findings indicate that tomato ripening was significantly influenced by both light and temperature. Tomatoes that matured under low-temperature conditions in the absence of light took more than three times longer to transition from the green stage to the breaker stage compared to those matured under high-temperature conditions with light exposure. Notably, tomato fruit maturation occurred at a faster rate under low-temperature and light conditions than under high-temperature and dark conditions. Changes in chlorophyll a fluorescence parameters were observed throughout the ripening process of tomato fruits. Tomato fruits ripened under low-temperature and dark conditions exhibited significantly lower NPQ (non-photochemical quenching) and R_FD (relative fluorescence decrease) values compared to other treatments, while their F_O (initial fluorescence) and F_M (maximum fluorescence) values were higher. The accumulation of sugar in tomato fruits was observed to be more influenced by light than temperature. On the other hand, the highest levels of phenolic content and lycopene were observed in tomato fruits matured under high-temperature and light conditions. Antioxidant activities, as measured by ABTS and DPPH assays, were highest in mature tomato fruits under high-temperature and light conditions, while they were lowest in fruits under low-temperature and dark conditions. In conclusion, this study highlights the critical role of temperature and light as crucial environmental factors influencing tomato maturation. Understanding these factors can contribute to optimizing postharvest conditions and enhancing fruit quality in the tomato industry.

The aim of this study was to evaluate growth response of two greenhouse-grown strawberry cultivars grown under two different relative humidity (RH) regimes using photo-physiological measurements, such as photosynthetic rate and photosynthesis efficiency (with the initial chlorophyll fluorescence curve part of 0-30millisec (OJIP) transients). The two different RH regimes (< 40% and > 60% RH) were maintained during daylight hours from November 20, 2018 to December 20, 2018. After 15 days of controlled humidity treatment, we found significant differences in photosynthetic rates, stomatal conductance, energy flux trapped by one active photosystem II reaction center (TRo/RC), and rate of electron transport flux of photosystem II reaction center (ETo/RC) values relative to cultivar type and RH. However, after 30 days of humidity treatment, the significant differences in these photosynthesis related parameters were responses related to RH treatment effects regardless of the cultivars. Both 'Arihyang' and 'Keumsil' cultivars grown under > 60% RH (during the day) showed higher root activity, reflecting multiple turnover of QA reductions (Ss), TRo/RC, and ETo/RC values than when grown under < 40% RH. In addition, relative variable chlorophyll fluorescence at 2millisec (Vj) and relative variable chlorophyll fluorescence at 30millisec (Vi) values were higher in the 'Arihyang' cultivar (regardless of RH) than in the 'Keumsil' cultivar. We conclude that maintaining high relative humidity inside greenhouses during the cold season (when RH is naturally low) will optimize strawberry fruit yield by enhancing root activity and photosynthetic rates.

The rainy season occurs mainly from June to July in Korea, and this season causes insufficient ambient light intensity for the growth of cherry tomato in a greenhouse. Titanium dioxide (TiO₂), as a photocatalyst, is known to affect photosynthesis in plants. This study was carried out to investigate the influence of TiO₂ foliar spray application on the yield and photophysiological responses of cherry tomato under low ambient light intensity during the rainy season in a greenhouse. Cherry tomato plants were treated with 100 mg·L⁻¹ TiO₂ (T1) or 200 mg·L⁻¹ TiO₂ (T2) nanoparticle suspension on 26 June. The control group was not treated with TiO₂. In the O–J phase of the OJIP transient under a cloudy day (2 July), the slope in the control and T1 groups rose more sharply than that in the T2 group. Conversely, on a clear day (10 July), the J–I phase of the T2 group sharply increased compared to that of the control and T1 groups. On a cloudy day with low ambient light intensity, the rate of electron transport flux from QA to QB per photosystem II reaction center (ET₀/RC) and carbon dioxide (CO₂) fixation of TiO₂-treated plants were increased compared to those of the control. However, on a clear day of high light intensity, the ET₀/RC and CO₂ fixation of the T2 group were lower than those of the control and Tl groups. The yield of fruit was increased in the T1 group over that in other treatments. TiO₂ treatment reduced the size of the fruit and delayed the ripening time, but greatly increased the fruit hardness. These results suggest that setting the concentration and supply amount of TiO₂ nanoparticles suitable for various environmental conditions should be prioritized in order to improve the effect of TiO₂ nanoparticles in tomato cultivation.