A comparison of the effects of drought on proline accumulation and peroxidases activity in leaves of Festuca rubra L. and Lolium perenne L.

The effect of soil drought on leaf water content, proline content, and the activity of guaiacol (GuPX) and ascorbate (APX) peroxidases as well as the level of lipid peroxidation were investigated in leaves of drought resistant red fescue (Festuca rubra) and drought sensitive perennial ryegrass (Lolium perenne). Plants were grown under glasshouse conditions in soil pot culture. 26 day-old grasses were exposed to drought by withholding irrigation for 18 days. Water content in leaves of perennial ryegrass decreased more than in red fescue throughout the experimental period. On the other hand, proline content (PC) was higher in red fescue. The activity of APX and GuPX increased in leaves of red fescue, while it did not change in perennial ryegrass. Our data demonstrate that both red fescue and perennial ryegrass were able to survive applied drought, as shown by a lack of stress-induced lipid peroxidation and hence no evidence of oxidative damage. We speculate, that the observed drought stress tolerance at cellular level was associated with the ability to accumulate proline, and to maintain high activity of APX and GuPX, resulting in protection against oxidative damage and lipid peroxidation. It seems that this mechanism works better in red fescue

Drought Stress Responses: Coping Strategy and Resistance

Plants’ resistance to stress factors is a complex trait that is a result of changes at the molecular, metabolic, and physiological levels. The plant resistance strategy means the ability to survive, recover, and reproduce under adverse conditions. Harmful environmental factors affect the state of stress in plant tissues, which creates a signal triggering metabolic events responsible for resistance, including avoidance and/or tolerance mechanisms. Unfortunately, the term ‘stress resistance’ is often used in the literature interchangeably with ‘stress tolerance’. This paper highlights the differences between the terms ‘stress tolerance’ and ‘stress resistance’, based on the results of experiments focused on plants’ responses to drought. The ability to avoid or tolerate dehydration is crucial in the resistance to drought at cellular and tissue levels (biological resistance). However, it is not necessarily crucial in crop resistance to drought if we take into account agronomic criteria (agricultural resistance). For the plant user (farmer, grower), resistance to stress means not only the ability to cope with a stress factor, but also the achievement of a stable yield and good quality. Therefore, it is important to recognize both particular plant coping strategies (stress avoidance, stress tolerance) and their influence on the resistance, assessed using well-defined criteria

A comparison of the effects of drought on proline accumulation and peroxidases activity in leaves of Festuca rubra L. and Lolium perenne L.

The effect of soil drought on leaf water content, proline content, and the activity of guaiacol (GuPX) and ascorbate (APX) peroxidases as well as the level of lipid peroxidation were investigated in leaves of drought resistant red fescue (Festuca rubra) and drought sensitive perennial ryegrass (Lolium perenne). Plants were grown under glasshouse conditions in soil pot culture. 26 day-old grasses were exposed to drought by withholding irrigation for 18 days. Water content in leaves of perennial ryegrass decreased more than in red fescue throughout the experimental period. On the other hand, proline content (PC) was higher in red fescue. The activity of APX and GuPX increased in leaves of red fescue, while it did not change in perennial ryegrass. Our data demonstrate that both red fescue and perennial ryegrass were able to survive applied drought, as shown by a lack of stress-induced lipid peroxidation and hence no evidence of oxidative damage. We speculate, that the observed drought stress tolerance at cellular level was associated with the ability to accumulate proline, and to maintain high activity of APX and GuPX, resulting in protection against oxidative damage and lipid peroxidation. It seems that this mechanism works better in red fescue

Cell membrane stability in two barley genotypes under water stress conditions

The effect of water stress induced in vitro by polyethylene glycol 6000 (PEG) and under drought stress on cell membrane stability was examined in two barley genotypes, the cultivar Aramir and line R567. The injury of cell membranes was markely influenced by leaf age, leaf position on the stem, and the degree of drought stress. The differences in percentage of injury to cell membrane between these genotypes were also found. The cv. Aramir exhibited a lower percentage injury value as compared to line R567, measured in vitro by PEG test. Similarly, under drought stress the cv. Aramir showed higher cell membrane stability than the line R567, even in severe stress. The results indicated also that both genotypes differ in the ability to adjust their cell membranes to water stress

Water deficit-induced membrane injury and oxidative stress in two barley genotypes

The purpose of this paper was to examine the effect of water deficit on membrane injuries, superoxide radical generation and lipid peroxidation in the leaves of two barley genotypes. Six-day-old seedlings of the cv. Aramir and line R567 were used in the experiments. According to our earlier work these genotypes significantly differ in the level of membrane injuries under water deficit conditions. Water stress was applied directly to leaves or to roots. The stress caused considerable membrane injuries in the leaves of all genotypes investigated.The percentage membrane injury was higher in the line R567 than in the cv. Aramir. Water stress imposed on leaves caused higher membrane injuries than water stress imposed on roots. The water stress treatment followed by an oxidative stress in the leaves. Line R567 having noticeably larger membrane injuries also exhibited a higher level of superoxide radical generation than the cv. Aramir. The level of lipid peroxidation increased in the both genotypes under the conditions of water stress imposed on leaves, but not on roots

Evaluation of Ambient Ozone Effect in Bean and Petunia at Two Different Sites under Natural Conditions: Impact on Antioxidant Enzymes and Stress Injury

Tropospheric ozone is a harmful air pollutant and greenhouse gas that adversely affects living organisms. The effect of long-term ozone stress on the activity of SOD, APX, and GuPX, as well as lipid peroxidation and membrane injury in bean and petunia growing at a city site and in a forest, characterised by different ozone concentrations, was examined. The experiments were conducted in three growing seasons with different tropospheric ozone concentrations and meteorological conditions. Plants’ exposition to increased ozone concentration resulted in enhanced activity of antioxidant enzymes, level of lipid peroxidation, and membrane injury. In all years, higher ozone levels and solar radiation were observed at the forest site. The pattern of the changes in enzyme activity was dependent on ozone concentrations as well as on environmental conditions and varied from year to year. In the second year with the highest ozone concentration, the activity of GuPX and SOD increased the most. However, despite higher ozone concentration in the forest, a larger increase in APX and SOD activity in both species and GuPX activity in bean was recorded at the city site. The present results revealed that plant response to ozone might vary in different locations not only due to differences in ozone concentration but also because of the impact of other environmental factors, such as solar radiation and temperature

Does Potassium Modify the Response of Zinnia (<i>Zinnia elegans</i> Jacq.) to Long-Term Salinity?

Salinity is one of the major abiotic stress factors hindering crop production, including ornamental flowering plants. The present study examined the response to salt stress of Zinnia elegans ‘Lilliput’ supplemented with basic (150 mg·dm−3) and enhanced (300 mg·dm−3) potassium doses. Stress was imposed by adding 0.96 and 1.98 g of NaCl per dm−3 of the substrate. The substrate’s electrical conductivity was 1.1 and 2.3 dS·m−1 for lower potassium levels and 1.2 and 2.4 dS·m−1 for higher potassium levels. Salt stress caused a significant and dose-dependent reduction in leaf RWC, increased foliar Na and Cl concentrations, and reduced K. About 15% and 25% of cell membrane injury at lower and higher NaCl doses, respectively, were accompanied by only slight chlorophyll reduction. Salt stress-induced proline increase was accompanied by increased P5CS activity and decreased PDH activity. More than a 25% reduction in most growth parameters at EC 1.1–1.2 dS·m−1 but only a slight decrease in chlorophyll and a 25% reduction in the decorative value (number of flowers produced, flower diameter) only at EC 2.3–2.4 dS·m−1 were found. Salt stress-induced leaf area reduction was accompanied by increased cell wall lignification. An enhanced potassium dose caused a reduction in leaf Na and Cl concentrations and a slight increase in K. It was also effective in membrane injury reduction and proline accumulation. Increasing the dose of potassium did not improve growth and flowering parameters but affected the lignification of the leaf cell walls, which may have resulted in growth retardation. Zinnia elegans ‘Lilliput’ may be considered sensitive to long-term salt stress

Evaluation of cell membrane injury in caraway (Carum carvi L.) genotypes in water deficit conditions

The aim of the study was to evaluate the resistance of caraway genotypes to water deficit based on the estimation of cell membrane stability (CMS) in leaves using polyethylene glycol (PEG) test. In 2007 and 2008, 25 selected caraway genotypes, originating from European botanical gardens (18), cultivars (2) and our own breeding strains (5), were tested. The plant material was collected from the experimental field. The obtained results showed highly significant differences in cell membrane injuries (p = 0.001) among investigated genotypes. The rank of genotypes in membrane injury index in 2007 was similar to that of 2008. Caraway genotypes originating from Warsaw (49.4%), Cracow (45.3%), Reykiavik (39.9%), Berlin (23.8%), Wisley (22.7%) and strains 9/2 (23.7%), 60/8 (22.2%) exhibited a high level of injury, which showed weak CMS and their high sensitivity to drought. The lowest extent of membrane injury was observed in genotypes originating from Bayreuth (4.2%), Ulm (4.4%), Cluj (5.5%), Lousanne (6.8%) and cultivar "Kończewicki" VI/4 (6.2%), which proves low sensitivity of these genotypes to water deficit and cell membrane stability. These genotypes may be used in further breeding program to improve caraway resistance to drought

Salicylic acid — A potential biomarker of tobacco Bel-W3 cell death developed as a response to ground level ozone under ambient conditions

Salicylic acid content and benzoic acid 2-hydroxylase (BA2H) activity were investigated in tobacco Bel-W3 and Bel-B leaves after exposure to tropospheric ozone in the conditions of ambient air. Plants were exposed in accordance with a standard methodology for ozone biomonitoring, in a three-year experiment. Free salicylic acid (SA), conjugated with glucose (SAG), and as a product of the BA2H activity was quantified with HPLC. In order to evaluate ozone injuries of leaves, an open source image analysis software was employed. Plants exposure to ambient ozone resulted in enhanced BA2H activity and intensified salicylic acid biosynthesis in leaves of Bel-W3 cultivar showing visible ozone injuries. The BA2H activity significantly correlated with SAG for ozone-exposed Bel-W3 plants. Both injuries and salicylic acid biosynthesis rate depended on the growth phase of leaves and nearly linear correlation between SA content and injuries was found for particular leaves of Bel-W3