The effects of a long-term (6-day) exposure to low positive temperature (4°С, LT treatment) and short-term (3 h per a day for 6 days) daily temperature drops to 4°С (DROP treatment) on leaf respiration in winter wheat (Triticum aestivum L., var. Moskovskaya 39) were studied under controlled conditions. In the case of the LT treatment, the respiration rate in the darkness (R_d) increased by 36%, while the DROP treatment only resulted in a tendency to such an increase. The influence of both DROP and LT treatments on the respiration rate in the light (R_l) and temperature sensitivity of R_d and R_l was insignificant. In contrast to the DROP treatment, the LT treatment increased the level of light-induced inhibition of plant respiration. In both LT- and DROP-treated plants, the rate of gross photosynthesis (A_g) measured at 12°С increased by 23 and 54%, respectively, as compared to the control plants. The DROP treatment did not affect the R_d/A_g and R_l/A_g ratios in plant leaves. The R_d/A_g value in LT-treated plants measured at 22°С was higher than in control plants, while the R_l/A_g value measured at 12°С was lower than in the control. The DROP treatment did not affect the sensitivity of respiration to salicylhydroxamic acid (SHAM), an inhibitor of the alternative respiratory pathway. The LT treatment increased the share of a SHAM-sensitive respiration in the total respiration of plant leaves by 25% on average, which indirectly indicates the activation of an alternative pathway of the electron transfer in the respiratory chain. Thus, a long-term continuous exposure of winter wheat seedlings to low positive temperatures provided a modifying effect on respiration manifested via changes in the respiratory rate, activity of the SHAM-sensitive respiration, and the ratio between respiration and gross photosynthesis. In the case of a short-term daily exposure to low temperature high respiration stability was observed.

Contamination of agricultural soils with heavy metal leads to a decrease in the crop quality and yield, as well as increases in public health risks. In this study, we aimed to evaluate the impact of soil contamination with lead (Pb) on the growth, photosynthesis, respiration, and coupling between these physiological processes, as well as temporal dynamics of Pb uptake and accumulation by lettuce (Lactuca sativa L.) plants. For this 46-day pot experiment, Pb(NO₃)₂ was mixed with loamy Retisol soil with the rate of 0, 50, and 250 mg kg⁻¹. No significant differences in plant biomass accumulation were found between plants grown on Pb-free and Pb-rich soil, but root-weight ratio, root-to-shoot weight ratio, and leaf area were lower, and the number of leaves and leaf weight per unit area were significantly higher in plants grown on soil contaminated with Pb than in their counterparts grown on Pb-free soil. The concentration of Pb in plant root and shoot followed the increase in soil Pb, with Pb content in the roots being higher than in the shoots. Soil Pb decreased chlorophyll content, net CO₂ assimilation rate and photosynthetic light use efficiency, but caused an increase in the leaf respiration rate regardless of whether respiration was performed in the light or in darkness. Increased ratio of respiration to photosynthesis reflects the shift in the carbon balance of lettuce plants toward carbon losses under stress conditions of soil contamination with Pb.

The absence of an externally-imposed 24 h light/dark cycle in closed plant production systems allows setting the light environmental parameters in unconventional ways. Innovative lighting modes for energy-saving, high-quality, and yield production are widely discussed. This study aimed to evaluate the effects of the light/dark cycles of 16/8 h (control) and 24/12 h, 48/24 h, 96/48 h, 120/60 h (unconventional cycles) based on the same total light amount, and continuous lighting (360/0 h) on plant performance of some Solanaceae species. Responses of eggplant (Solanum melongena L.), sweet pepper (Capsicum annuum L.), tobacco (Nicotiana tabacum L.), and tomato (Solanum lycopersicum L.) plants to extended light/dark cycles and continuous lighting were studied under controlled climate conditions. Plants with two true leaves were exposed to different light/dark cycles for 15 days. Light intensity was 250 µmol m⁻² s⁻¹ PPFD, provided by light-emitting diodes (LEDs). After the experiment, tomato, sweet pepper, and eggplant transplants were planted in a greenhouse and grown under identical conditions of natural photoperiod for the estimation of the after-effect of light treatments on fruit yield. Extended light/dark cycles of 24/12 h, 48/24 h, 96/48 h, 120/60 h, and 360/0 h affected growth, development, photosynthetic pigment content, anthocyanin and flavonoid content, and redox state of plants. Effects varied with plant species and length of light/dark cycles. In some cases, measured parameters improved with increasing light/dark periods despite the same total sum of illumination received by plants. Treatments of tomato and pepper transplants with 48/24 h, 96/48 h, and 120/60 h resulted in higher fruit yield compared to conventional 16/8 h photoperiod. The conclusion was made that extended light/dark cycles can result in increased light use efficiency compared to conventional photoperiod and, therefore, reduced product cost, but for practical application, the effects need to be further explored for individual plant species or even cultivars.

To reduce the use of commercial conventional inorganic fertilizers, the possibility of using pulp and paper industry wastes in agriculture as an alternative source of nutrients is recently under study and discussion. This work aimed to evaluate the effect of sodium lignosulfonate application to soil on photosynthetic leaf nutrient (N, P, K, Ca, Mg, Fe, Mn, and Na) and water use efficiency. A pot culture experiment was conducted with cucumber seedlings, using five lignosulfonate concentrations (0, 1, 2.5, 5, and 10 vol. %) in sandy soil under sufficient or low nutrient availability for plants. The impact of nutrient availability on the plants’ physiological traits was stronger than the lignosulfonate impact. Under sufficient nutrient availability, the lignosulfonate application resulted in decreased photosynthetic N, P, K, Ca, Mg, Fe, and Na use efficiency. Cucumber growth and development, and photosynthetic nutrient, water, and light use efficiency were significantly reduced with a nutrient deficiency. The sodium lignosulfonate application was not successful in eliminating the negative effects of nutrient deficit on cucumber seedlings.

Cucumber ( Cucumis sativus L.), tomato ( Solanum lycopersicum L.), and sweet pepper ( Capsicum annuumL.) plants were subjected daily over 13 days to short-term (2 h) temperature drops to 12, 8, 4,...

Salicylhydroxamic acid (SHAM) is used in studies of plant respiratory metabolism as a specific inhibitor of alternative cyanide-resistant oxidase (AOX). The sensitivity of respiration in intact plant tissues to SHAM provides indirect evidence for electron transport through the AOX-mediated pathway (AOP) in the respiratory electron transport chain. In this study, chilling-sensitive plants (cucumber (Cucumis sativus L.), tomato (Solanum lycopersicum L.), and sweet pepper (Capsicum annuum L.)) were exposed daily to short-term drops of temperature (to 12, 8, 4, and 1°С) by the end of night periods, and the effects of DROP treatments on SHAM-resistant and SHAM-sensitive respiration of leaves were examined. When leaf respiration in cucumber and tomato plants was measured at optimum temperature (25°C), it showed an increase after the DROP treatments; this phenomenon was caused by the activation of SHAM-sensitive respiration ascribed mainly to AOP activity. At low measurement temperature (15°C), the DROP treatments stimulated total respiration and SHAM-resistant respiration of cucumber leaves, which indicates the activation of electron flow through the cytochrome oxidase pathway (COP). Remarkably, the COP activity increased with the severity of DROP treatment. At high temperature (35°C), the respiration of cucumber leaves became less sensitive to SHAM, whereas SHAM-resistant respiration increased with the severity of DROP treatments. The contribution of the SHAM-sensitive component to the total leaf respiration in cucumber increased with the temperature during measurements. Upon changes in temperature, the SHAM-sensitive respiration in cucumber exhibited larger variations than the SHAM-resistant component, which implies a significant contribution of COP to the respiratory chilling tolerance. Our data suggest that although AOP pathway respiration plays an important role in respiratory activity of chilling-sensitive plants, COP pathway is the main mechanism for maintaining the respiration during low-temperature treatments.