Sunflower (Helianthus annuus L. cv. SH222) plants and calli were exposed to KCl stress for three weeks. Calli were more tolerant to KCl than plants. KCl stress decreased NO(-)(3), Mn, Fe and B levels in whole plants and P, Ca and Mg in shoots. NO(-)(3), P, Ca, Mg, Mn, and B levels decreased in 100 mM-stressed calli. Chlorophyll content, F:(m) and (F:(m)-F:(0))/F:(m) ratio decreased in stressed leaves, while F:(0) increased only in leaves exposed to severe stress (100 and 150 mM). Membrane permeability and lipid peroxidation increased in plants under all stress conditions and in 100 and 150 mM stressed calli, but remained unchanged in 25 mM stressed calli. Salt stress also induced changes relating to antioxidant enzymes: plants under all stress conditions showed a decrease in catalase, peroxidase and SOD activities. Calli under moderate stress (25 mM KCl) showed an increase of catalase, peroxidase and SOD activities, but the activities of peroxidase and SOD decreased when calli were exposed to higher KCl concentrations. The decrease of antioxidant enzyme activities is in tune with lipid peroxidation and membrane permeability increases. On the other hand, calli adapted for 6 months to 100 mM KCl showed an increase of these enzyme activities compared to unstressed calli, while MDA production and membrane permeability were not significantly affected.

No abstract

Field and greenhouse studies have been conducted to clarify aspects of population dynamics and NaCl tolerance of Salicornia ramosissima J. Woods. Two populations, Varela and Verdemilho, were monitored in the field during two consecutive life cycles and aspects of their morphology and density were recorded monthly. In the laboratory seedlings were exposed to different salinity for 10 weeks and growth and mortality rate were recorded weekly. The growth of the populations differed significantly, possibly because of the different salinities of the two sampling sites and/or genetic adaptations of the two populations to the environmental conditions. The absence of a significant correlation between sediment salinity and stem elongation suggested, however, that salinity, alone was not responsible for the differences observed and was possibly associated with other factors, because of nutritional, edaphic, and microclimatic conditions. S. ramosissima did not develop well in conditions of elevated or moderate salinity; its growth was optimum at low salinity. Optimum development of S. ramosissima may, nevertheless, depend on the total number of large seeds in a population seed bank, because of their greater success in germination and germinability under stress conditions than small seeds.

Sunflower (Helianthus annuus L. cv. SH222) plants and calli were exposed to KCl stress for three weeks. Calli were more tolerant to KCl than plants. KCl stress decreased NO(-)(3), Mn, Fe and B levels in whole plants and P, Ca and Mg in shoots. NO(-)(3), P, Ca, Mg, Mn, and B levels decreased in 100 mM-stressed calli. Chlorophyll content, F:(m) and (F:(m)-F:(0))/F:(m) ratio decreased in stressed leaves, while F:(0) increased only in leaves exposed to severe stress (100 and 150 mM). Membrane permeability and lipid peroxidation increased in plants under all stress conditions and in 100 and 150 mM stressed calli, but remained unchanged in 25 mM stressed calli. Salt stress also induced changes relating to antioxidant enzymes: plants under all stress conditions showed a decrease in catalase, peroxidase and SOD activities. Calli under moderate stress (25 mM KCl) showed an increase of catalase, peroxidase and SOD activities, but the activities of peroxidase and SOD decreased when calli were exposed to higher KCl concentrations. The decrease of antioxidant enzyme activities is in tune with lipid peroxidation and membrane permeability increases. On the other hand, calli adapted for 6 months to 100 mM KCl showed an increase of these enzyme activities compared to unstressed calli, while MDA production and membrane permeability were not significantly affected.

No abstract