Correlation between frost tolerance and antioxidant activities in cereals

Frost-tolerant and frost-sensitive cereal species were hardened at low, nonfreezing temperature. Changes in the activity of antioxidant enzymes (catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione-S-transferase and glutathione reductase) in the crown and leaves were determined in the control and in hardened plants. The highest correlation between enzyme activity and frost tolerance was found in the case of guaiacol peroxidase and ascorbate peroxidase from hardened leaves. Enzyme activities in the crown and in unhardened leaves showed no significant positive correlation

Investigation of antioxidant activity in maize during low temperature stress

Young maize inbred lines and their hybrids were tested for chilling tolerance using the chlorophyll fluorescence induction technique. The genotypes were ranked based on the decrease in the Fv/Fm parameter after chilling stress at 5°C. The activities of certain antioxidant enzymes were determined in control and cold-treated plants. The results suggest that although there are differences between the genotypes in the activities of almost all the antioxidant enzymes, these differences do not reflect the differences in chilling tolerance

Effect of elevated atmospheric CO2 level on the abiotic and biotic stress tolerance of cereals

Abstract Effect of elevated CO2 level (EC) was studied on the tolerance of cereals to elevated temperature and drought and on the resistance of wheat to fungal diseases. In general, elevated growth temperature did not affect final grain size, thus having less harmful effects than heat stress or drought during grain-filling. The plants subjected to low water supply levels or elevated temperature had higher biomass and grain yield at EC than at the ambient level. Susceptible wheat varieties were, however, usually more prone to diseases when grown at EC, while resistant varieties remained resistant even at EC

Influence of salicylic acid on phytochelatin synthesis in Zea mays during Cd stress

Abstract: Presoaking maize (Zea mays) seeds in salicylic acid (SA) reduces damage caused by cadmium. In the present work the possible role of phytochelatins (PCs) in SA-mediated protection against Cd toxicity was investigated. Seeds were presoaked in 0.5 mM SA, and seedlings were grown in hydroponic solution containing 0, 0.01, 0.015, or 0.025 mM Cd. Treatment with Cd increased the PC levels in maize roots, but only slight changes were observed in the leaves. Long-term exposure to Cd decreased the phytochelatin synthase (PCS) activity in the roots and led to an increase in PCS and glutathione reductase (GR) activities in maize leaves. Although presoaking seeds in SA solution before exposure to Cd may reduce the level of heavy metal injury and has an effect on the composition of individual PCs, this protection is not directly connected with the altered regulation of PCs

COMPARATIVE STUDY OF VIABILITY MEASUREMENT METHODS IN CROP PLANTS

The aim of the present study was to find the best way of measuring the viability of root and leaf samples from various plant species (pea, wheat and maize) exposed to different concentrations of the heavy metal Cd. A comparison was made of three viability tests, namely electrolyte leakage measurements, and TTC and NBT reduction. The results suggested that electrolyte leakage was the most useful method for measuring leaf viability, being simple, fast, reliable and reproducible. The TTC reduction measurement proved the most useful for maize roots, while NBT reduction was the best method for detecting the viability of pea and wheat roots

Drought stress and polyamines in maize

Drought is one of the most common environmental stresses that affect growth, development and in turn yield of crop plants. Thus, understanding of plant responses to drought and investigations on compounds capable of reducing the stress sensitivity of plants are of great importance and crucial to progress in genetic engineering and/or conventional breeding. Polyamines (PAs), which are small, positively charged, aliphatic amines found in all plant cells, are able to bind to negatively charged molecules, e.g. nucleic acids, acidic phospholipids and various types of proteins, thus having a protective role under stress conditions. Results of several studies suggested that PAs can be promising compounds for the reduction of abiotic stress sensitivity in plants, since both seed priming and adding PAs to the hydroponic solution have been shown to protect various plant species against abiotic stress factors. Many reports have indicated that the stress tolerance of plants is correlated with their capacity to enhance the synthesis of PAs upon exposure to stress. In addition, mutant and transgenic Arabidopsis plants with altered PAs synthesis pointed to involvement of PAs in different abiotic and biotic stresses responses and have elucidated their key functions in stress signaling networks in plants; however the exact mechanism remains enigmatic. The main questions of the present study are: 1. how influence PA treatment PEG-induced drought stress in maize? 2. is the statement: “the more PAs, the better” true in this case? 3. if not, what are the reasons

Speculation: Polyamines are important in abiotic stress signaling

The main role of polyamines was originally assumed to be as direct protective compounds important under stress conditions. Although in some cases a correlation was found between the endogenous polyamine content and stress tolerance, this relationship cannot be generalized. Polyamines should no longer be considered simply as protective molecules, but rather as compounds that are involved in a complex signaling system and have a key role in the regulation of stress tolerance. The major links in polyamine signaling may be H2O2 and NO, which are not only produced in the course of the polyamine metabolism, but also transmit signals that influence gene expression via an increase in the cytoplasmic Ca2+ level. Polyamines can also influence Ca2+ influx independently of the H2O2- and/or NOmediated pathways. Furthermore, these pathways may converge. In addition, several protein kinases have been shown to be influenced at the transcriptional or post-translational level by polyamines. Individual polyamines can be converted into each other in the polyamine cycle. In addition, their metabolism is linked with other hormones or signaling molecules. However, as individual polyamines trigger different transcriptional responses, other mechanisms and the existence of polyamine-responsive elements and the corresponding transacting protein factors are also involved in polyamine-related signaling pathways

Szalicilsav által szabályozott védekező mechanizmusok vizsgálata gabonafélékben = Investigation of protective mechanisms controlled by salicylic acid in cereals

A pályázat célja az volt, hogy megvizsgáljuk az exogén szalicilsav (SA) hatását különböző abiotikus stresszek során, valamint hogy megvizsgáljuk hogyan alakul az endogén SA szint stresszkörülmények között gabonafélékben. Hidegstressz során nem volt különbség a kontroll és a SA kezelt növények membránlipidjeinek zsírsavösszetételében, míg a SA előkezelés megemelte a putreszcin és a spermidin szintjét, és ez is hozzájárul valószínűleg a SA védőhatásához. Szárazság stressz ellen a SA nemcsak, hogy nem nyújtott védelmet, hanem fokozta annak károsító hatását. Nehézfémstressznél (Cd) a SA kezelés hatására gyökérben jobban csökkent a fitokelatin szintáz enzim aktivitása, míg levélben megnőtt. Szárazság stressz során kukorica (Norma hibrid) mind a kötött, mind a szabad endogén SA szint lecsökkent gyökérben, míg levélben drasztikus stressz hatására megnőtt. NaCl kezelésnél a levélben a szabad SA szint kismértékben megnőtt, gyökérben nem változott, a kötött mind levélben, mind gyökérben lecsökkent. Cd stressz során gyökérben mind a szabad mind a kötött SA tartalom megnőtt. Az abszcizinsav kezelés normál hőmérsékleten nem befolyásolta az SA szintet, míg egy nap 5°C-os alacsony hőmérsékleti stressz során a szabad SA szint megnőtt, a kötött pedig lecsökkent, mind levélben, mind gyökérben. Ezek alapján megállapíthatjuk, hogy a szalicilsav szerepet játszik abiotikus stresszek során. | The aim of the project was to examine the effect of exogenous salicylic acid (SA) during various types of abiotic stress, and to determine how the endogenous SA level changed under stress conditions in cereals. During cold stress no difference was observed in the fatty acid composition of membrane lipids between control and SA-treated plants, while preliminary treatment with SA caused a rise in the levels of putrescine and spermidine, probably contributing to the protective effect of SA. Rather than providing protection against drought stress, SA made the damage more severe. In the case of heavy metal (Cd) pollution the phytochelatin synthase enzyme activity was further reduced by SA in the roots, but increased in the leaves. During drought stress there was a reduction in the level of both bound and free endogenous SA in the roots of maize (hybrid Norma), while it increased in response to drastic stress in the leaves. Treatment with NaCl caused a slight increase in the free SA level in the leaves, while no change was observed in the roots; the bound SA level declined in both leaves and roots. During Cd stress there was an increase in both free and bound SA content in the roots. At normal temperature abscisic acid treatment had no effect on the SA level, but after one day of low temperature stress (5°C) there was an increase in free SA and a drop in bound SA in both leaves and roots. It is thus clear that salicylic acid plays a role in the response to abiotic stress factors

Abscisic acid may alter the salicylic acid-related abiotic stress response in maize

The effect of abscisic acid (ABA) treatment on chilling tolerance and salicylic acid (SA)-related responseswas investigated in young maize seedlings. Although the pre-treatment of plants with ABA slightly decreased the chlorophyll content, it also reduced the level of chilling injury caused by 6 days of cold treatment at 5 ̊C. Under normal growth conditions increased levels of bound SA and of bound ortho-hydroxycinnamic acid (oHCA) were observed in the leaves during ABA treatment. In the roots ABA did not affect the free and bound SA levels, but increased the amount of free and bound oHCA. The activity of glutathione-S-transferase (GST) increased on the 3rd day of ABA treatment, while it did not change when followed by cold stress, compared to the control leaves. In the roots the activities of glutathione reductase, GST and ascorbate peroxidase (APX) increased during the ABA treatment, and those of GST and APX were also stimulated when ABA pre-treatment was followed by cold stress, compared to the control roots. Our results suggest that an overlap may exist between the ABA-induced cold acclimation and the SA-related stress response

Exploration of cold signalling related to ascorbate and salicylic acid in Arabidopsis thaliana

TLow temperature is a significant limiting factor on plant development in the temperate zones. We tried to explore certain steps of the cold-signalling focused on salicylic acid (SA) and ascorbic acid (AA) using Arabidopsis thaliana as a model. The results of the freezing survival tests showed that both the wild type and mutant plants had better freezing tolerance after cold hardening treatment. SA deficient plants showed a higher survival rate. Two of the polyamines, putrescine and spermine showed only significant changes under the cold hardening. Significant differences were found in the bound SA level between the temperature treatments, but it did not correlate with the AA level and the survival rates