Effect of Cd treatment on phytochelatin synthesis in maize

Phytochelatins are Cys-rich peptides enzymatically synthesized by γ-Glu-Cys dipeptidyl transpeptidase, generally known as phytochelatin synthase. In the present work the enzymes of phytochelatin synthesis and cadmium (Cd) accumulation were investigated during Cd stress. Young maize plants were treated with 0.1 mM Cd for 48 hours. Roots and leaves were used for the experiments. The Cd was accumulated mainly in young leaves during the treatment but there was also accumulation in older leaves. In the roots the amount of Cd increased continuously. The Cd concentration was much higher in the roots than in the leaves. There were no changes in the photosynthetic parameters. The γ-glutamylcysteine synthetase (γ-ECS) activity did not change in the first six hours but there was a great increase in activity after one day. The activity of glutathione synthetase did not change in the leaves but increased to a slight extent in the roots after one hour. The phytochelatin synthase activity did not change after one day, but decreased on the 2nd day in the roots. An increase in the activity could be seen in the leaves during the 1st day, after which it remained constant

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

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

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

Effect of salt stress on the endogenous salicylic acid content in maize (Zea mays L.) plants

Two-week-old maize plants were treated with 50 or 100 mM NaCl for seven days. Leaves and roots were collected for measurements on salicylic acid and antioxidant enzyme activity on the 1st, 3rd and 7th days of treatment and after four days of recovery. The quantum yield of photosystem II decreased after 7 days in maize plants treated with 100 mM NaCl. There were no changes in the catalase and ascorbate peroxidase activity. The glutathione-S-transferase, glutathione reductase and guaiacol peroxidase activities increased. There were no changes in the level of endogenous free and bound salicylic acid. The free o-hydroxy-cinnamic acid (oHCA) content increased after 7 days in the leaves, while the bound oHCA level increased after 4 days of recovery. It has been concluded that oHCA may play an important role in stress processes

Role of light in freezing tolerance of wheat

During the frost hardening of wheat plants light intensity is a key factor in the development of frost tolerance, and several processes, including lipid metabolism, antioxidant activity, polyamine synthesis and salicylic acid signalling, may also contribute to light-enhanced freezing tolerance. The results suggest that there are at least two type of receptors, one cold-and one light-dependent, which induce signal transduction processes leading to freezing tolerance

Alacsony hőmérsékleti stressztolerancia és antioxidáns aktivitás közti kapcsolat vizsgálata gabonaféléknél = Investigation of the connection between tolerance to low temperature stress and antioxidant activity in cereals

A kutatási munka célja a gabonafélék stressztűrő képességének kialakításában szerepet játszó szabályozási folyamatok jobb megismerése volt, különös tekintettel a reaktív oxigénformák mennyiségének szabályozását végző antioxidáns rendszerekre. Több gazdasági növény, elsősorban kukorica és búza esetében jellemeztük az antioxidáns enzimrendszerek hozzájárulását abiotikus stresszfaktorok elleni védelemben. Kimutattuk, hogy a különböző gabonafajok eltérő stratégiákat dolgoztak ki a reaktív oxigénformák mennyiségének szabályozásához. Igazoltuk a fény szerepét a búza maximális fagyállóságának kialakulásában. Ehhez kapcsolódóan bemutattuk a ciklikus elektrontranszportlánc, egyes antioxidánsok, a szalicilsav-metabolizmus, valamint a membránlipidek alakulását eltérő fényviszonyok melletti alacsony hőmérsékleti edzés során. Eredményeink azt mutatják, hogy a szalicilsavfüggő jelátviteli utak szerepének tanulmányozásakor nemcsak magára a szalicilsavra, hanem egyes prekurzorainak a változásaira is figyelemmel kell lenni. Mindemellett bizonyítottuk, hogy intakt levelekben az egy elektronátmenetet megengedő fényfelvillanás általi gerjesztés egy összetett termolumineszcencia sávot eredményez, melynek magasabb hőmérsékleti (40 °C körüli) komponense egy AG-sáv. Jellemeztük az AG termolumineszcencia sávot, és bemutattuk alkalmazását gazdasági növények stressztűrő képességének vizsgálatában. | The research aimed to obtain a better insight into the regulatory processes involved in the development of stress tolerance in cereals, with special regard to antioxidant systems that regulate the quantity of reactive oxygen species (ROS). The contribution of antioxidant enzyme systems to defence against abiotic stress factors was investigated in several crops, particularly maize and wheat. Different cereal species were found to have elaborated diverse strategies for the regulation of ROS quantities. Light was proved to play a role in the achievement of maximum frost resistance in wheat. In this connection, changes occurring in the cyclic electron transport chain, in various antioxidants, in the salicylic acid metabolism and in membrane lipids during low temperature hardening were investigated under varying light conditions. It was found that when studying the role of salicylic acid-dependent signal transduction pathways it is important to consider not only salicylic acid itself, but also changes in its precursors. In addition it was demonstrated that in intact leaves a single turnover flash resulted in a complex thermoluminescence band, the high temperature (~ 40°C) component of which is an AG band. The latter was analysed, and its application in determining the stress tolerance of crops was discussed