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How chrysanthemum (Chrysanthemum × grandiflorum) ‘Palisade White’ deals with long-term salt stress
AbstractSalinity is a serious problem in the cultivation of ornamental plants. Chrysanthemum (Chrysanthemum × grandiflorum) ‘Palisade White’ was evaluated in order to examine its responses to long-term salt stress. Plants were grown in substrate supplemented with NaCl doses (g dm−3 of substrate) 0, 0.44, 0.96, 1.47, 1.98, 2.48 and 2.99. The initial electrical conductivity (EC) of the substrates was 0.3, 0.9, 1.4, 1.9, 2.6, 3.1 and 3.9 dS m−1, respectively. Plant growth, relative water content (RWC), Na, Cl, K, N and P concentrations, membrane injury (MI), chlorophyll and proline levels, as well as gas exchange parameters in leaves of chrysanthemum were determined. A dose-dependent significant reduction of growth and minor decrease of leaf RWC were observed. Foliar Na and Cl concentrations increased with the highest NaCl dose up to 6-fold. However, the concentration of K increased by about 14 %, N by about 5 % but P decreased by about 23 %. Membrane injury was rather low (11 %) even at the highest NaCl dose. Statistically significant decreases of stomatal conductance (20 %), transpiration rate (32 %) and photosynthesis (25 %) were already observed at the lowest NaCl dose and about 40 % decrease of all these parameters with the highest dose. A significant reduction in the intercellular CO2 concentration occurred at the lower NaCl doses and no changes with the highest dose. These results show that in plants grown with the highest NaCl dose, non-stomatal limitation of photosynthesis may occur. According to Maas and Hoffman tolerance assessment (1977) chrysanthemum ‘Palisade White’ may be considered as moderately sensitive to salt stress in terms of growth inhibition. However, it is able to cope with long-term salt stress without any signs of damage, such as chlorophyll depletion, leaf browning or necrotic spots probably due to maintenance of K homeostasis and proline accumulation, which alleviate the toxic effect of chloride.
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.