Izabela Marcińska

Alleviation of Osmotic Stress Effects by Exogenous Application of Salicylic or Abscisic Acid on Wheat Seedlings

The aim of the study was to assess the role of salicylic acid (SA) and abscisic acid (ABA) in osmotic stress tolerance of wheat seedlings. This was accomplished by determining the impact of the acids applied exogenously on seedlings grown under osmotic stress in hydroponics. The investigation was unique in its comprehensiveness, examining changes under osmotic stress and other conditions, and testing a number of parameters simultaneously. In both drought susceptible (SQ1) and drought resistant (CS) wheat cultivars, significant physiological and biochemical changes were observed upon the addition of SA (0.05 mM) or ABA (0.1 μM) to solutions containing half-strength Hoagland medium and PEG 6000 (−0.75 MPa). The most noticeable result of supplementing SA or ABA to the medium (PEG + SA and PEG + ABA) was a decrease in the length of leaves and roots in both cultivars. While PEG treatment reduced gas exchange parameters, chlorophyll content in CS, and osmotic potential, and conversely, increased lipid peroxidation, soluble carbohydrates in SQ1, proline content in both cultivars and total antioxidants activity in SQ1, PEG + SA or PEG + ABA did not change the values of these parameters. Furthermore, PEG caused a two-fold increase of endogenous ABA content in SQ1 and a four-fold increase in CS. PEG + ABA increased endogenous ABA only in SQ1, whereas PEG + SA caused a greater increase of ABA content in both cultivars compared to PEG. In PEG-treated plants growing until the harvest, a greater decrease of yield components was observed in SQ1 than in CS. PEG + SA, and particularly PEG + ABA, caused a greater increase of these yield parameters in CS compared to SQ1. In conclusion, SA and ABA ameliorate, particularly in the tolerant wheat cultivar, the harmful effects and after effects of osmotic stress induced by PEG in hydroponics through better osmotic adjustment achieved by an increase in proline and carbohydrate content as well as by an increase in antioxidant activity.

The influence of animal sex hormones on the induction of flowering in Arabidopsis thaliana: comparison with the effect of 24-epibrassinolide

The influence of selected steroids on the in vitro generative development of Arabidopsis thalianawas investigated. The activity of the animal steroids androsterone, androstenedione, progesterone, estrone, estriol, and 17β-estradiol was compared to 24-epibrassinolide, a member of the regulatory family of brassinosteroids. A. thaliana plants were cultured in vitro in media containing these steroids. The stimulatory effect of the tested substances was evaluated by measurement of the percentage of generative plants versus vegetative plants in the experimental group. It was established that androstenedione, the main testosterone precursor, and androsterone, a typical male hormone, were more effective in stimulating flowering in A. thaliana than the female hormones, estrogens and progesterone. Androsterone at a concentration of 0.1 μM increased the percentage of generative plants up to 96% (control 41%). Estrogens at the same concentration decreased the number of generative plants and 24-epibrassinolide did not stimulate A. thalianagenerative development.

Cytokinins in shoot apices of Brassica napus plants during vernalization

The putative role of cytokinins in processes leading to reproductive development of plants was investigated by analysing the shoot apical parts of a winter cultivar of oilseed rape (Brassica napus L. var. oleifera, cv. Górczański). The endogenous cytokinin levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS) in the shoot apices of vegetative plants (grown at 20/17°C with a 16/8h day/night regime) and vernalized plants (56 days at 5/2°C with a 16/8h photoperiod) at different times during floral transition. During vernalization, the content of all isoprenoid cytokinins increased significantly, coinciding well with the onset of the early stages of reproductive development. Cytokinin levels reached their maxima when most of the plants became irreversibly reproductive (after 42 days of cold treatment). cis-Zeatin riboside (unequivocally identified by quadrupole-time-of-flight MS) accounted for ca. 87-89% of the total isoprenoid cytokinin content in control and vernalized plants, whilst N(6)-isopentenyladenosine ( approximately 6% in control and approximately 8% in vernalized plants) and cis-zeatin (approxiamtely 2% in control and approximately 1% in vernalized plants) were the next most abundant cytokinins. In the post-vernalization period, endogenous cytokinin levels decreased, but remained significantly higher in the reproductive plants than in the vegetative controls. These results suggest that cytokinins, especially those of the cis-zeatin type, are involved in vernalization-induced reproductive development of B. napus.

The relations between drought susceptibility index based on grain yield (DSIGY) and key physiological seedling traits in maize and triticale genotypes

The physiological reasons for the differences in sensitivity of C3 and C4 plant species to environmental stresses have not been thoroughly explained. In this study the effects of drought stress on the growth and selected physiological traits were examined in the seedlings of 13 single cross maize (C4 plant) hybrids and 11 spring triticale (C3 plant) breeding lines and varieties differing in drought sensitivity. For plants in the seedling stage the results demonstrated a genetic variation in dry matter accumulation of shoots and roots (DWS, DWR), number (N) and length (L) of particular components (seminal, seminal adventitious, nodal) of the root system, membrane injury by soil drought (LID), osmotic and high temperature stress (LIOS, LIHT), water potential (ψ), water loss (WL), grain germination in osmotic stress (FG, PI), and seedling survival (SS). Seedlings grown under moderate soil drought showed a decrease in dry matter of the top parts and roots and a decrease in the length of seminal, seminal adventitious and nodal roots in comparison to seedlings grown in control conditions. The observed harmful effects of drought stress were more distinct in drought sensitive genotypes. Used in this paper drought susceptibility indexes (DSIGY) were calculated in other experiment by determining the changes in grain yield (GY) under two soil moisture levels (irrigated and drought). The variation of DSIGY for maize ranges from 0.381 to 0.650 and for triticale from 0.354 to 0.578. The correlations between DSIGY and laboratory tests (LI, FG, SS) confirmed that they are good indicators of drought tolerance in plants. The highest values of genetic variation were observed in LI, DWS, SS and WL and the lowest in the measurements of ψ FG, PI, LS, LSA and LN. The correlation coefficients between LIOS and LIHT tests were, in most of the considered cases, statistically significant, which indicates that in maize and triticale the mechanisms of membrane injury caused by simulated drought or high temperature are physiologically similar. It can be concluded that an approach to the breeding of maize and triticale for drought tolerance using these tests can be implemented on the basis of separate selection for each trait or for all of them simultaneously. In that case, it would be necessary to determine the importance of the trait in relation to growth phase, drought timing and level, as well as its associations with morphological traits contributing to drought tolerance. The obtained values of the correlation coefficient between laboratory tests suggest that the same physiological traits may be applied as selection criteria in drought tolerance of maize and triticale genotypes.

Erratum to: The relationship between seedling growth and grain yield under drought conditions in maize and triticale genotypes

The effects of drought stress on seedlings’ growth and grain yield of 13 single cross maize hybrids and 11 breeding lines and cultivars of spring triticale were studied in greenhouse and field experiments. In the field experiment, the drought susceptibility index (DSIGY) was calculated by determining the change in grain yield (GY) in conditions with two soil moisture levels (IR, irrigated; D, drought). In the greenhouse experiment the response to soil drought was evaluated using DSIDW, by determining changes in the dry weight (DW) of vegetative plant parts. Marked variations in GY and DW were observed among the studied genotypes. In control conditions, the GY and DW in drought-sensitive genotypes were higher compared to the drought-resistant ones; but in drought conditions, the decreases in GY and DW in resistant genotypes were smaller than in drought-sensitive ones. DSIGY and DSIDW revealed variations in the degree of drought tolerance among the examined maize and triticale genotypes. The values of DSIGY in the field experiment and DSIDW in the greenhouse experiment enabled a division of the studied genotypes into drought-resistant or -sensitive groups. A close correlation between DSIGY and DSIDW was found. The positive linear correlation and determination coefficients between DSIGY and DSIDW were statistically significant (P = 0.05), being equal to R2 = 0.614 (maize) and R2 = 0.535 (triticale). The ranking of the studied genotypes based on DSIGY was in most cases consistent with the ranking based on DSIDW, which indicates that genetically conditioned drought tolerance is similar for plants in the seedling and reproductive growth stages or may at least partly have a common genetic background.

The Effects of Electric Current on Flowering of Grafted Scions of Non-Vernalized Winter Rape

Non-vernalized scions were grafted onto vernalized stocks in winter rape (Brassica napus L. var. oleifera, cv. Górczański). The grafted plants were subjected to electric current (30 V for 30 s or 6 V for 24 h) and the percentage of flowering scions was recorded. The negative polarity with cathode (−) attached to the scion and anode (+) left close to the roots inhibited greatly the percentage of flowering. The reverse polarity enhanced flowering markedly under short days and only slightly promoted flowering under long days. Attachment of electrodes without passing a current had no effect on flowering.

Production of double haploids in oat (Avena sativa L.) by pollination with maize (Zea mays L.)

The aim of the study was to optimize the method of oat haploid production by pollination with maize. Seventeen oat genotypes were used in the experiment. Various factors influencing the growth and development of ovaries and embryo production were investigated: genotype, time of pollination, growth regulators and time of their application. Emasculated before anthesis, oat florets were pollinated with maize pollen after 0, 1 or 2 days. Next, one of two auxins analogues (2,4-D or dicamba) were applied to oat pistils. These auxins had no significant influence on the number of enlarged ovaries and embryos. The time of application of these growth regulators had a significant influence on embryo production. Haploid embryos were obtained from all used genotypes, although the frequency of enlarged ovaries and obtained embryos did not differ markedly between the genotypes. On average, 85% of ovaries were enlarged and 11.7% of them produced haploid embryos. Depending on the regeneration medium, 24–41% of embryos were germinated, of which 12% had developed into green plants. A strong significant difference in the number of germinating embryos and haploid plants was observed between the kind of regenerating medium used. There were no albino plants and all the obtained plants were haploid.

Transfer of the ability to flower in winter wheat via callus tissue regenerated from immature inflorescences

Using two wheat varieties (Triticum aestivum L., winter ‘Grana’ and spring ‘Jara’) the ability of callus from immature inflorescences to differentiate into new plants was studied. In the case of the winter wheat the requirement for vernalization of the newly developed plants to attain the ability for heading was investigated.Callus was developed from 1–2 mm fragments of immature inflorescences, 5–10 mm in length, on Murashige and Skoog medium containing 1 mg l-1 2,4-d, 3% sucrose and 0.6% agar, at 25° C and in continuous light of about 6.4 W m-2 PAR energy. After 6 weeks of culture green centres of differentiation were observed. During the following 4 weeks culture on MS medium free of 2,4-d, leaf-like structures as well as a small number of roots were obtained. The regenerants were rooted on a half-strength MS medium, then transferred to pots of soil and placed in a glasshouse with 16 h photoperiod at a temperature day/night 23/17° C.After about 6 weeks of culture in the glasshouse, almost all regenerants (98%) headed and were fertile, producing normal seeds, including the winter variety. The heading of winter plants under conditions excluding vernalization indicates that the callus tissue derived from a generative organ transmits the state of generative induction onto the developing new plants.

Electric current affects the rate of development in isolated apical parts of rape in vitro

Apical parts of stems of Brassica napus L. var. oleifera cv. Gorczanski (winter rape) and cv. Mlochowski (spring rape), grown in vitro, were subjected to direct electric current (DC) of different polarity, duration and voltage. The positive orientation of DC, i.e. anode attached to the apical part and cathode to the medium, markedly enhanced the differentiation of the apical meristem in winter rape. The reverse polarity was without effect. DC treatment of positive polarity resulted in spring rape in transition of all explants to generative state while 70 % of non-treated plants remained at vegetative stage. Even negative orientation of DC brought about a rise in percentage of flowering plants with regard to control. The developmental effects of DC were dependent only to a low degree or not at all on duration and voltage of the treatment.

Mammalian androgen stimulates photosynthesis in drought-stressed soybean

The aim of the present studies was to assess the possibility of compensating the negative effects of drought stress on gaseous exchange and efficiency of photosystem II in soybean seedlings by application of the androgen — androstenedione. Androstenedione (0.25 mg dm−3) was applied via presowing seed soaking (12 h). Control seeds were untreated with steroid. Plants were cultured in pots. On the 12th day of growth, the plants were watered for the last time. Drought symptoms occurred during the next 10 days. On the 22nd day of growth, leaf gaseous exchange and PSII measurements were taken. Afterwards the plants were watered. Two days later measurements were taken again. Androstenedione improved the intensity of leaf net photosynthesis. The effect of androstenedione was manifested during the rehydration of plants that have undergone a period of drought. An increase in net photosynthesis intensity was accompanied by higher transpiration. Possible mechanisms of androstenedione action — effect on aquaporin functionality and membrane stability — are discussed. The significance of ethanol and DMSO (solvents of steroid) in experiments on the physiological activity of androstenedione is also considered.