High light causes disturbances in photosynthetic phosphorylation or damage to the photosystem II (PSII) structure or even assimilation tissues. The value of the red/far-red ratio (R/FR) provides the plant with information on the environmental light conditions, regulating, among others, photosynthetic activity and pigment composition of the plant. The response of the photosynthetic apparatus of the sporotrophophylls and nest leaves of Platycerium bifurcatum, grown for 6 months at the low or high R/FR ratio, were studied. Later, the plants were transferred to high light (1,200 μmol quantum · m−2 · s−1).
Changes in PSII photochemical activity were determined based on non-destructive methods of chlorophyll a fluorescence kinetics analysis. The measurement of radiation reflectance from the leaves allowed to determine the content of selected pigments related to the photosynthesis process and to assess changes in the Photochemical Reflectance Index. The calculation of reflectance difference and sensitivity analysis was used to identify so-called “stress-sensitive wavelengths”.
Results and discussion
Plant growth at high R/FR ratio prepares photosynthetic apparatus of ferns to high light and enables more efficient conversion of absorbed photons. The increase in the amount of photoprotective compounds allows the protection against photoinhibition in the sporotrophophyll leaves that play key roles in plant nutrition and reproduction.
Authors:Magdalena Troć, Diana Saja, Andrzej Kornas, Anna Żuraw, and Andrzej Skoczowski
In order to better understand the processes of allelopathic interactions and to elucidate the impact of various herbal extracts on seedling growth, investigations were initiated using isothermal calorimetry as a monitor. Seeds of wheat, mustard, rape and clover were germinated on aqueous herbal extracts from arnica, hypericum, milfoil, ribwort, sage and sunflower for 24 h (until the root was visible). Then, five seedlings were put into a calorimeter ampoule with herbal extracts. The specific thermal power (=heat production rate) of the seedlings during their growth was measured by isothermal calorimetry at 20 °C. Heat rate data were collected for 48 h. As a control seedlings were grown on water. The patterns of the thermal power–time curve during seedling growth on the herbal extracts and on water were completely different. In comparison with the water control, seedling growth on the herbal extracts was accompanied by a strong exothermic peak (first phase), whereas in the second phase distinct endothermic peaks were observed. The time after which the maxima of exo- and endothermic peaks occurred strongly depended on the seedling species and the origin of herbal extract. Similarly, the total thermal effect connected with seedling growth was correlated with the seedling species and herbal extract type.
Authors:Andrzej Skoczowski, Magdalena Troć, Anna Baran, and Małgorzata Baranska
The subject of the study was investigation of impact of extracts from sunflower and mustard leaves on growth of mustard seedlings. Seeds of mustard were germinated on water and then grew on aqueous extracts from sunflower or mustard leaves. The specific thermal power during seedlings growth was measured by isothermal calorimetry. Changes in the chemical composition stimulated by extracts were measured by FT-Raman spectroscopy and analyzed with the support of the cluster analysis. The heat production rate during growth of seedlings was related to the type of extracts. Crude sunflower and mustard extracts strongly inhibited the growth of seedlings when compared to non-treated control. FT-Raman spectroscopy confirms that allelopathic compounds have the greatest influence on the metabolism of fatty acids of mustard cotyledons. The obtained results indicate that sunflower and mustard extracts have varied impact on growth and heat production rate of mustard seedlings.
Authors:Andrzej Skoczowski, Anna Janeczko, Gábor Gullner, István Tóbias, Andrzej Kornas, and Balázs Barna
The aim of the study has been to determine the protection effect of brassinosteroid (BR27) in oilseed rape cotyledons against infection by an incompatible wild type of, a hypersensitive response mutant of and saprophytic Pseudomonas bacteria. In this paper, membrane permeability, PSII efficiency and metabolic activity were analysed. The following strains of Pseudomonans were used: P. syringae pv. syringae (Ps), P. syringae pv. syringae hrcC mutant (Pm) and P.fluorescence (Pf). The study was carried out using two cultivars of spring oilseed rape (Brassica napus L.): ‘Licosmos’ and ‘Huzar’. Pre-treatment of cotyledons with BR27 caused about 50–70% increase in ion leakage for both cultivars. However, BR27 significantly decreased ion leakage from cotyledons inoculated with Ps in both cultivars. Infection with Ps and Pf caused disturbances of energy flow in PSII by lowering its efficiency in rape cotyledons. We noted insignificant impact of 24-epibrassinolide on PSII efficiency if compared to absolute control, but generally it had a positive effect in plants infected with bacteria. The values of heat flow in all treatments, except for cotyledons infected with Ps, decreased during 20 h after inoculation. However, the curves of heat flow for Ps-infected cotyledons showed a completely different pattern with at least two peaks. BR27 pre-treated cotyledons infected with Ps had higher heat flow in comparison to Ps infected ones. BR27 treatment did not change specific enthalpy of cotyledon growth (Δgh) for both cultivars if compared with absolute control. However, infection with Ps markedly increased Δgh values by about 200% for both cultivars. We suggested protective action of BR27 in oilseed rape cotyledons after bacterial infection with Pseudomonas.