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Progressing climate change necessitates the search for solutions of plant protection against the effects of water deficit. One of these solutions could be silicon supplementation. The aim of the study was to verify the hypothesis that silicon changes aquaporin expression and antioxidant system activity in a direction which may alleviate the effects of drought stress in oilseed rape. The accumulation of BnPIP1, BnPIP2-1-7 and BnTIP1;1 aquaporins and the expression of their genes, the level of catalase, superoxide dismutase activities and hydrogen peroxide content as well as total non-enzymatic antioxidant activity were analyzed in leaf tissue from control and silicon-treated oilseed rape plants growing under well-watered and drought conditions. Silicon was applied in two forms - pure silicon and a silicon complex. It was shown that under drought conditions, both pure silicon and the silicon complex (with Fe) significantly increased the accumulation of aquaporins and improved the activity of enzymatic and non-enzymatic components of the antioxidant system, while under well-watered conditions, these effects were observed only in the case of the silicon complex. The presented study proves that silicon supplementation in oilseed rape improves the regulation of water management and contributes to the protection against oxidative stress caused by drought.

The aim of this study was to investigate the accumulation of silicon in oilseed rape and to characterize the changes in chosen water balance parameters in response to drought. The following parameters were estimated: water content, osmotic and water potential, evapotranspiration, stomatal conductance and abscisic acid level under optimal and drought conditions. It was shown that oilseed rape plants accumulate silicon after its supplementation to the soil, both in the case of silicon alone and silicon together with iron. It was revealed that silicon (without iron) helps maintain constant water content under optimal conditions. While no silicon influence on osmotic regulation was observed, a transpiration decrease was detected under optimal conditions after silicon application. Under drought, a reduction in stomatal conductance was observed, but it was similar for all plants. The decrease in leaf water content under drought was accompanied by a significant increase in abscisic acid content in leaves of control plants and those treated with silicon together with iron. To sum up, under certain conditions, silicon is accumulated even in non-accumulator species, such as oilseed rape, and presumably improves water uptake under drought stress.

Climate changes, which result in the occurrence of periods with relatively high temperatures during the winter, can lead to the deacclimation of cold-hardened plants and cause problems with their winter survival. The aim of these studies was to investigate the physiological changes (photosynthesis and water relations including aquaporin expression) that accompany deacclimation process in the economically important winter oilseed rape plants. The effect of deacclimation on frost tolerance was also estimated for two tested cultivars: semi-dwarf and plants of a normal height. After cold acclimation at 4 &deg, C (compared to the unacclimated control) the typical changes that accompany cold acclimation such as an increase in the content of water-soluble sugars or a lower water content in the leaves, which lead to an increased frost tolerance, were observed. Deacclimation partially or completely reversed these changes, which resulted in a decreased frost tolerance that was accompanied by a decrease in the content of sugars and an increase of the osmotic potential. The chemical composition of the leaves, which was measured using FT-Raman spectroscopy also clearly confirmed the metabolic differences between the cold-acclimated and deacclimated plants. The plants were significantly different in regard to the content of the various pigments as well as fatty acids and polysaccharides. The phenomenon of a deacclimation-induced decrease in aquaporin PIP1 accumulation, which was accompanied by unchanged PIP1 transcript accumulation, will be discussed in the aspects of the water relations and decreased frost tolerance in deacclimated plants.

The aim of study was to gain a deeper knowledge about local and systemic changes in photosynthetic processes and sugar production of pepper infected by Obuda pepper virus (ObPV) and Pepper mild mottle virus (PMMoV). PSII efficiency, reflectance, and gas exchange were measured 48 and/or 72 h after inoculation (hpi). Sugar accumulation was checked 72 hpi and 20 d after inoculation (as a systemic response). Inoculation of leaves with ObPV led to appearance of hypersensitive necrotic lesions (incompatible interaction), while PMMoV caused no visible symptoms (compatible interaction). ObPV (but not PMMoV) lowered Fv/Fm (from 0.827 to 0.148 at 72 hpi). Net photosynthesis decreased in ObPV-infected leaves. In ObPV-inoculated leaves, the accumulation of glucose, fructose, and glucose-6-phosphate was accompanied with lowered sucrose, maltoheptose, nystose, and trehalose contents. PMMoV inoculation increased the contents of glucose, maltose, and raffinose in the inoculated leaves, while glucose-6-phosphate accummulated in upper leaves.

The study was focused on the influence of salicylic acid (SA) on maize seeds germination and on some physiological and biochemical processes in maize plants growing in the hydroponic culture under copper (Cu) stress. A significant influence of SA pretreatment on the advanced induction of the maize seeds metabolic activity and the level of the endogenous SA in germinated seeds and developing roots have been stated. Although, the ability of maize seeds to uptake SA and accumulate it in the germinated roots was confirmed, the growth inhibition of Cu-stressed maize seedlings was not ameliorated by SA seeds pretreatment. Cu-stressed plants exhibited a decrease in the photosynthetic pigment concentration and the increase in non-photochemical quenching (NPQ) - an indicator of an excess energy in PSII antenna assemblies lost as a heat. The amelioration effect of SA application was found only for carotenoids content which increased in stressed plants. It was also shown that maize roots growing in stress conditions significantly differed in the chemical composition in comparison to the roots of control plants, but the SA pretreatment did not affect these differences. On the other hand, it was found that SA seed pretreatment significantly influenced the ability of stressed plants to accumulate copper in the roots. It was stated that a higher level of exogenous SA application led to a lower accumulation of Cu ions in maize roots. Custressed plants exhibited higher oxidative stress in roots than in leaves which was manifested as an increase in the concentration of hydrogen peroxide due to stress factor application. We observed an increase in catalase (CAT) activity in leaves of Cu-stressed plants which corresponded with a lower H_{2}O_{2} content when compared with roots where the hydrogen peroxide level was higher, and the inhibition of the CAT activity was found. Furthermore, we found that the SA seed pretreatment led to a decrease in the H_{2}O_{2} content in the roots of the Custressed plants, but it did not influence the H_{2}O_{2} level in leaves. The increase in hydrogen peroxide content in the roots of Cu-stressed plants correlated with a higher activity of the MnSODI and MnSODII isoforms. It was found that SA pretreatment caused a decrease in MnSODII activity accompanied by the decrease in H_{2}O_{2} concentration. Achieved results indicated also that the changes in the chemical composition of the root tissue under copper stress constituted protection mechanisms of blocking copper flow into other plant organs. However, it might be assumed that the root tissue remodelling under Cu stress did not only prevent against the Cu ions uptake but also limited the absorption of minerals required for the normal growth leading to the inhibition of the plant development.

Phytohormone levels and the expression of genes encoding key enzymes participating in hormone biosynthetic pathways were investigated in pepper leaves inoculated with two different tobamoviruses. Obuda pepper virus (ObPV) inoculation led to the development of hypersensitive reaction (incompatible interaction), while Pepper mild mottle virus (PMMoV) inoculation resulted in a systemic, compatible interaction. ObPV-inoculation markedly increased not only the levels of salicylic acid (SA) (73-fold) and jasmonic acid (8-fold) but also those of abscisic acid, indole-3-acetic acid, indole-3-butyric acid, cis-zeatin, cis-zeatin-9-riboside and trans-zeatin-9-riboside in the inoculated pepper leaves 3 days post inoculation. PMMoV infection increased only the contents of gibberellic acid and SA. Hormone contents did not change significantly after ObPV or PMMoV infection in non-infected upper leaves 20 days post inoculation. Concentrations of some brassinosteroids (BRs) and progesterone increased both in ObPV- and PMMoV inoculated leaves. ObPV inoculation markedly induced the expression of three phenylalanine ammonia-lyase (PAL) and a 1-aminocyclopropane-1-carboxylate oxidase (ACO) genes, while that of an isochorismate synthase (ICS) gene was not modified. PMMoV inoculation did not alter the expression of PAL and ICS genes but induced the transcript abundance of ACO although later than ObPV. Pre-treatment of pepper leaves with exogenous 24-epi-brassinolide (24-epi-BR) prior to ObPV-inoculation strongly mitigated the visible symptoms caused by ObPV. In addition, 24-epi-BR pre-treatment markedly altered the level of several hormones in pepper leaves following ObPV-inoculation. These data indicate that ObPV- and PMMoV-inoculations lead to intricate but well harmonized hormonal responses that are largely determined by the incompatible or compatible nature of plant-virus interactions.

The aim of this study was to investigate the accumulation of silicon in oilseed rape and to characterize the changes in chosen water balance parameters in response to drought. The following parameters were estimated: water content, osmotic and water potential, evapotranspiration, stomatal conductance and abscisic acid level under optimal and drought conditions. It was shown that oilseed rape plants accumulate silicon after its supplementation to the soil, both in the case of silicon alone and silicon together with iron. It was revealed that silicon (without iron) helps maintain constant water content under optimal conditions. While no silicon influence on osmotic regulation was observed, a transpiration decrease was detected under optimal conditions after silicon application. Under drought, a reduction in stomatal conductance was observed, but it was similar for all plants. The decrease in leaf water content under drought was accompanied by a significant increase in abscisic acid content in leaves of control plants and those treated with silicon together with iron. To sum up, under certain conditions, silicon is accumulated even in non-accumulator species, such as oilseed rape, and presumably improves water uptake under drought stress.

The influence of far-red light (FRL) was studied on the chemical composition of Spirulina platensis biomass. The following light compositions were used during the culture white light, blue-red LED light (BRL) and BRL supplemented with FRL (BRFRL). Chlorophyll and phenol contents were measured by spectrophotometric methods, whereas presence of carotenoids, lipids, and phycobiliproteins were estimated by Fourier-transform Raman spectrometry. Additionally, phenol content was investigated by fluorescence intensity of algae culture in the range of 430–650 nm. The content of chlorophyll and phenols in algae cells depended on the spectral composition of light and was the highest under BRL (16.7 ± 0.5 and 9.1 ± 0.6, respectively). It was shown that there is a positive linear correlation (R = 0.902 at p < 0.0000001) between the ratio of relative fluorescence intensity of S. platensis suspensions at 450 nm to the suspensions at 540 nm (F450/F540) and the content of phenolic compounds in the biomass. Changes in the F450/F540 ratio can explain approximately 80% changes of phenol contents in algae cells. Spirulina platensis Raman spectra demonstrated that the biomass of algae growing under white light and BRL had a significantly higher intensity of phycobiliprotein bands than the algae growing under BRFRL.

This study investigated the impact of mutation in the HvDWARF gene, encoding C6-oxidase involved in brassinosteroid (BR) biosynthesis, on disease resistance of barley against the fungal pathogen powdery mildew (Blumeria graminis f. sp. hordei). The mutation results in significant BR deficiency in leaf tissue. Since increase in the BR content by their exogenous application was reported to improve plant resistance to viral, bacterial and fungal infection, we wanted to find out, if lowered content of BR may affect plant resistance to this pathogen. The 527DK mutant carrying the aforementioned mutation and its respective wild type Delisa were inoculated by powdery mildew fungus (Bgh, race A6). However, no symptoms of disease were visually noted neither on 527DK nor on Delisa. Microscopic observations showed that after germination of the conidia the germ tubes started to penetrate, developed appressorium but could not develop further in the two genotypes. The cell wall thickening (papillae) around the penetration was only visible. However, inoculated plants showed changes in some of parameters describing photosynthetic efficiency or water relations. Similarly, alterations in hormonal homeostasis not only between wild type and mutant, but between control and infected plants were observed. Inoculation with the pathogen induced especially accumulation of compounds from auxin group (indole-3-carboxylic acid, oxindole-3-acetic acid, 4-chloroindole-3-acetic acid and 5-chloroindole-3-acetic acid). Interestingly, the stronger effect was observed in plants with mutation in the HvDWARF gene. Taking into account that the HvDWARF gene mutation finally did not affect resistance to powdery mildew (no symptoms appearance), we suggest that the conclusion of our study may be of importance for breeding of barley.

Leaves of a pepper cultivar harboring the L 3 resistance gene were inoculated with Obuda pepper virus (ObPV), which led to the appearance of hypersensitive necrotic lesions approx. 72 h post-inoculation (hpi) (incompatible interaction), or with Pepper mild mottle virus (PMMoV) that caused no visible symptoms on the inoculated leaves (compatible interaction). ObPV inoculation of leaves resulted in ion leakage already 18 hpi, up-regulation of a pepper carotenoid cleavage dioxygenase ( CCD ) gene from 24 hpi, heat emission and declining chlorophyll a content from 48 hpi, and partial desiccation from 72 hpi. After the appearance of necrotic lesions a strong inhibition of photochemical energy conversion was observed, which led to photochemically inactive leaf areas 96 hpi. However, leaf tissues adjacent to these inactive areas showed elevated ΦPSII and Fv/Fm values proving the advantage of chlorophyll a imaging technique. PMMoV inoculation also led to a significant rise of ion leakage and heat emission, to the up-regulation of the pepper CCD gene as well as to decreased PSII efficiency, but these responses were much weaker than in the case of ObPV inoculation. Chlorophyll b and total carotenoid contents as measured by spectrophotometric methods were not significantly influenced by any virus inoculations when these pigment contents were calculated on leaf surface basis. On the other hand, near-infrared FT-Raman spectroscopy showed an increase of carotenoid content in ObPV-inoculated leaves suggesting that the two techniques detect different sets of compounds.

The study aimed to determine the usefulness of isothermal calorimetry and FT-Raman spectroscopy for the early evaluation of rigid ryegrass resistance to fenoxaprop-P ethyl (active ingredient one of aryloxyphenoxypropionate herbicides). The calorimetric measurements were done on the 4-day-old seedlings of susceptible and resistant biotypes of rigid ryegrass (Lolium rigidum Goud.) for 72 h, at 20 °C. It was observed that the specific thermal power–timecurves of the susceptible and resistant biotypes growing on water (control) were qualitatively similar. Herbicides changed the shape of the specific thermal power–time curves of both biotypes. Furthermore, the total specific thermal energy was significantly higher for the seedlings of resistant biotype, growing both on water or herbicide, as compared to the susceptible ones. The analysis of the seedlings’ endosperm, conducted using FT-Raman spectroscopy, showed a weaker intensity of the bands in the spectra derived from the resistant biotype. Differences in the specific thermal power–time curves and FT-Raman spectra between susceptible and resistant biotypes growing on water indicate that the sensitive and resistant biotypes are metabolically and chemically different already in the early stages of the seedling growth. We conclude that isothermal calorimetry and FT-Raman spectroscopy are efficient tools for the early detection of rigid ryegrass resistance to fenoxaprop-P ethyl.

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.

Tribenuron-methyl is the active substance of the herbicide used for weed control in crops. The aim of this study was to investigate differences in the metabolic response of seeds, seedlings and leaves of Centaurea cyanus L., depending on the degree of resistance to tribenuron-methyl. Changes in the values of selected biochemical and physiological parameters (germination index, chemical composition, photochemical efficiency of photosystem II and the emission spectra of blue-green fluorescence) presented herein make it possible to determine the differences between cornflower biotypes with various types of resistance to the tested herbicide. Moreover, differences in the chemical composition of dry seeds between biotypes susceptible and resistant to tribenuron-methyl were observed before using the herbicide. The degree of resistance to the herbicide—resistant or susceptible, but not the types of this resistance-mutational or metabolic, can be distinguished on the basis of the presented parameters. These findings allow for early diagnosis of the resistance of cornflower to tribenuron-methyl. Additionally, we suggest that the described parameters might be used as physiochemical markers for early estimation of weed resistance to various types of herbicide. The presented conclusions are especially important for agricultural practice.