Parameters of illumination including the spectra, intensity, and photoperiod play an important role in the cultivation of plants under greenhouse conditions, especially for vegetables such as lettuce. We previously showed that illumination by a combination of red, blue, and white LEDs with a high red light intensity, was optimal for lettuce cultivation; however, the effect of the photoperiod on lettuce cultivation was not investigated. In the current work, we investigated the influence of photoperiod on production (total biomass and dry weight) and parameters of photosynthesis, respiration rate, and relative chlorophyll content in lettuce plants. A 16 h (light):8 h (dark) illumination regime was used as the control. In this work, we investigated the effect of photoperiod on total biomass and dry weight production in lettuce plants as well as on photosynthesis, respiration rate and chlorophyll content. A lighting regime 16:8 h (light:dark) was used as control. A shorter photoperiod (8 h) decreased total biomass and dry weight in lettuce, and this effect was related to the suppression of the linear electron flow caused by the decreasing content of chlorophylls and, therefore, light absorption. A longer photoperiod (24 h) increased the total biomass and dry weight, nevertheless an increase in photosynthetic processes, light absorption by leaves and chlorophyll content was not recorded, nor were differences in respiration rate, thus indicating that changes in photosynthesis and respiration are not necessary conditions for stimulating plant production. A simple model to predict plant production was also developed to address the question of whether increasing the duration of illumination stimulates plant production without inducing changes in photosynthesis and respiration. Our results indicate that increasing the duration of illumination can stimulate dry weight accumulation and that this effect can also be induced using the equal total light integrals for day (i.e., this stimulation can be also caused by increasing the light period while decreasing light intensity). Increasing the duration of illumination is therefore an effective approach to stimulating lettuce production under artificial lighting.

The effects of different spectral compositions of light-emitting diode (LED) sources and fertilizer containing biologically active silicon (Si) in the nutrient solution on morphological and physiological plant response were studied. Qualitative indicators and the productivity of plants of a red-leaved and a green-leaved lettuce were estimated. Lettuce was grown applying low-volume hydroponics in closed artificial agroecosystems. The positive effect of Si fertilizer used as a microadditive in the nutrient solution on the freshly harvested biomass was established on the thirtieth day of vegetation under LEDs. Increase in productivity of the red-leaved lettuce for freshly harvested biomass was 26.6%, while for the green-leaved lettuce no loss of dry matter was observed. However, being grown under sodium lamps, a negative impact of Si fertilizer on productivity of both types of plants was observed: the amount of harvested biomass decreased by 22.6% and 30.3% for the green- and red-leaved lettuces, respectively. The effect of using Si fertilizer dramatically changed during the total growing period: up to the fifteenth day of cultivation, a sharp inhibition of the growth of both types of lettuce was observed; then, by the thirtieth day of LED lighting, Si fertilizer showed a stress-protective effect and had a positive influence on the plants. However, by the period of ripening there was no effect of using the fertilizer. Therefore, we can conclude that the use of Si fertilizers is preferable only when LED irradiation is applied throughout the active plant growth period.

This article proposes a new method for determining the pathological state of a plant, based on a combination of the method for measuring the dynamics of photosystem II pigment fluorescence in the leaves of L. sativa plants and analyzing the resulting time series using bispectral analysis based on the wavelet transform. The article theoretically shows a possible mechanism for the appearance of a peak on the map of bispectrum indexes during nonlinear analog conversion of a physiological signal in a biological object. The phenomenon of increasing the degree of nonlinearity in the transmission of an external periodic signal in plant signaling systems has been experimentally demonstrated.

Modern developments in data analysis techniques and evolutionary optimization algorithms have made it possible to analyze large amounts of unstructured digital data sets. Based on the differential evolution algorithm and semiclassical quantum simulations, we have recently proposed a method for classifying and analyzing the optical properties of organic pigments. In this paper, we present the results of modeling the absorption spectra of five carotenoids synthesized during the vital activity of the ascomycetous fungi: neurosporaxanthin, neurosporene, torulene, γ-carotene, and ζ-carotene. We calculated the absorption spectra for each pigment using the multimode Brownian oscillator theory, which allows us to evaluate the influence of molecular vibrations on the electronic transitions in the pigment. We applied a generalized spectral density function method to our modeling, taking into account the contributions of 13 vibrational modes with frequencies varying between 100 cm⁻¹ and 3000 cm⁻¹. This approach allowed us to gain a deeper understanding of how molecular vibrations affect the absorption spectra of these organic compounds. Thus, each absorption spectrum was associated with a unique set of Huang–Rhys factors (which represent the effective electron–phonon interaction). This set can be considered as a kind of “fingerprint” that characterizes the optical response of the pigment in the solvent.

При выращивании растений в светокультуре эффективными являются энергосберегающие светодиодные облучатели, имеющие длительный срок службы, низкую теплоотдачу и небольшие габариты, а также возможность близкого расположения к растениям и регулирование интенсивности и спектров освещения. С целью оценки влияния режимов излучения на растения и затрат энергии при данных режимах исследовалась продуктивность растительной продукции капусты японской сорта Мизуна Ред и их биохимический состав. Растения освещали специально разработанными светодиодными лампами производства ВИМ с динамически регулируемым спектральным составом по 4 каналам. Экспериментальные исследования проводились при трёх режимах излучения: непрерывном (контроль), импульсном и сканирующем с общей фотосинтетической активной радиацией 321 мкмоль/м²с в пропорции B:G:R:FR (синий: зеленый: красный: дальне красный спектры) ~ 30:26:38:6. Параметры формирования надземной массы и сухого вещества определялись дважды на 15 и 30 дни вегетационного периода. Установлено, что при импульсном режиме излучения содержание пищевых волокон в листьях по сравнению с непрерывным освещением (контролем) больше на 64,3%, зольных веществ – на 19,1%. Отмечается повышенное содержание аскорбиновой кислоты и холина. Применение импульсного режима излучения позволило повысить содержание углеводов в тканях побегов Мизуна Ред на 71,4% по сравнению со сканирующим режимом.