The chotts in Algeria are temporary salt lakes recognized as important wintering sites of water birds but neglected in terms of the diversity of the insects living on their banks. Around a chott in the wetland complex in the high plains near Constantine (eastern Algeria), more than half of the species of plants are annuals that dry out in summer, a situation that prompted us to sample the vegetation in spring over a period of two years. Three zones were identified based on an analysis of the vegetation and measurements of the salt content of the soils. Surveys carried out at monthly intervals over the course of a year revealed temporal and spatial variations in biodiversity and abundance of grasshoppers. The inner zone is colonized by halophilic plants and only one grasshopper species (Dericorys millierei) occurs there throughout the year. Two polyphagous species of Calliptamus, which can feed on halophilic plants migrate from adjacent areas into the inner zone in August to feed on the plants growing there. The other species of grasshoppers remain in outer zones as they are unable to feed on halophilic plants. The greatest abundance of grasshoppers from August to winter was recorded in the inner zone and in spring and early summer in the outer zones. The dependence of D. millierei on bushes of Amaranthaceae and its moderate flight ability, features of the family Dericorytidae, limit this species ability to colonize neighbouring chotts., Sarah Mahloul, Abboud Harrat, Daniel Petit., and Obsahuje bibliografii
To investigate the photoprotection of energy dissipation and water-water cycle, a C3 euhalophytic herb, Suaeda salsa L., was exposed either to chilling temperature (4°C) accompanied by moderate irradiance (600 μmol m-2 s-1) (CM) and/or to chilling temperature (4°C) accompanied by low irradiance (100 μmol m-2 s-1) (CL). During chilling stress, both the maximal photochemical efficiency of PSII (Fv/Fm) and the oxidizable P700 decreased in S. salsa leaves either under CM or CL, which indicated the severe photoinhibition. Relative to Fv/Fm, the oxidizable P700 decreased markedly under CL, which indicated that PSI was more sensitive to CL treatment than PSII. Initial fluorescence, number of closed PSII centers, and nonphotochemical quenching increased under CM, but more markedly under CL in S. salsa leaves. Activity of superoxide dismutase and ascorbate peroxidase was higher under CM than that under CL. The production of reactive oxygen species (ROS) decreased first and then increased under both treatments, but the content of O2.- and H2O2 was higher under CL than that under CM after 12 h of chilling stress. These results suggested that photoinhibition in S. salsa might be related to the accumulation of reactive oxygen species (ROS) induced by excess energy. The water-water cycle could not dissipate energy efficiently under CL, which caused the great accumulation of ROS., N. Sui., and Obsahuje bibliografii
Photosynthesis has walked into the path of evolution for over millions of years. Organisms relying directly on photosynthesis, when subjected to adverse environments for a long duration, experience retardation in their growth and development. Salinity stress is perceived as one of the major threats to agriculture as it can cause an irreversible damage to the photosynthetic apparatus at any developmental stage of the plant. However, halophytes, a special category of plants, carry out all life processes, including photosynthesis, without showing any compromise even under high saline environments. The fascinating mechanism for Na+ exclusion from cytosol besides retaining photosynthetic efficiency in halophytes can provide a valuable genetic resource for improving salt stress tolerance in glycophytes. Understanding how plants stabilize their photosynthetic machinery and maintain the carbon balance under saline conditions can be extremely useful in designing crops for saline and dry lands., S. Wungrampha, R. Joshi, S. L. Singla-Pareek, A. Pareek., and Obsahuje bibliografické odkazy