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The effect of salt stress on the growth of the Atriplex hortensis was determined by growing plants in soils receiving a one-time irrigation of nutrient solution containing low, medium, and high levels of NaCl. Atriplex plants were grown in sand culture under controlled greenhouse conditions. The experiment was compared to two varieties of A. hortensis. Growth and yield were progressively declined by increasing NaCl concentrations. Atriplex hortensis, an annual halophyte, exhibits significant reduction in height and biomass under saline stress conditions. The photosynthetic activity decreases when plants are grown under saline conditions leading to reduced growth and productivity. Low levels of salinity (5 g/l NaCl) did not cause substantial inhibition of growth but increasing concentrations of salt induced a progressive decline in length and weight of the plants. Salt stress induced a significant decrease in leaf area, but it had no significant effect on leaf water content. The results of present study indicate no differences in salinity tolerance in both Atriplex plants. Another possible conclusion is that improved tolerance to salt stress may be accomplished by decline in growth and photosynthetic activity. Based on these findings the tolerant Atriplex can be grown in moderately NaCl-contaminated soils.

Among the plants studied, var. purpurea was the most efficient in accumulating Pb and Zn in its shoots, whereas var. rubra was most suitable for phytostabilization of sites contaminated with Cu and Ni.

The impact of salinity and water stress was analyzed in the xero-halophyte Atriplex hortensis using two varieties: green orach (A. hortensis var. purpurea) and red orach (A. hortensis var. rubra). A. hortensis L. is a C 3 species well adapted to salt and drought conditions. To collect information on the physiological impact of different salt and water deficit levels on their water stress resistance, plants were exposed for 3 months to solution containing four levels of NaCl or to water stress regimes including four levels of field capacity. Osmotic potential at zero turgor W s 0 , osmotic potential at full turgor (W s 100 ), relative water content (RWC), ion concentration (Na ? , K ? , Ca 2? , Mg 2? , and Cl -), and malondialdehyde (MDA) were determined at the end of the treatment. The salinity and water stress induced a decrease in W s 100 , W s 0 , and RWC in both varieties, recorded changes being higher in plants of red variety than those of green variety. Both varieties specifically accumulated Na ? in response to drought and salt stress, suggesting that this element could play a physiological role in the stress response of this xero-halophyte species. In contrast, the presence of NaCl and water stress induced a decrease in K ? , Ca 2? , and Mg 2? concentration in both varieties. Salinity clearly induced an increase in Cl -concentration in all tissues, but water stress had no impact on this parameter. MDA concentration increased in response to water stress and exogenous NaCl. Based on these findings the more drought-tolerant red orach may be grown in water-limiting soils.

Aleppo pine had a large forest cover in North Africa and along the Mediterranean basin which management is not fully developed and new forest tools are required. In this research, the forest structure, epidometric characteristics and allometric relationships were studied in 79 plots covering four bioclimatic zones from natural even aged forests of Aleppo pine located between eastern Algeria to the western coastal part of Tunisia. To characterize the forest structure three sampling methods were carried out: classical inventories (recording all pine trees), and two simplified approach using one average size or five dominant pine tree per plot. Annual growth increment and cone production were only calculated for the average size tree. Furthermore, the analysis of variance showed non-significant differences recorded between bioclimatic zones in trunk or crown diameter using the two simplified approach. Moreover, a significant decrease from wetter to drier areas in total height, crown height, cone seed production was observed only for average size tree method. However, the analysis of covariance showed significant differences between both approaches in total height, trunk diameter and crown coverage which were largely influenced by the pine tree density. In future investigations, we confirmed previous research that the dominant tree is a good sampling method to examine the site fertility, whereas the average size tree constitutes a valuable approach to study the population growth and reproduction.Key words: Pinus halepensis Mill.; bioclimatic zones; forest structure; sampling approach; increment; reproductive characteristics. ResumenMétodos alternativos de muestreo para estimar la estructura y caracteres reproductivos de bosques de pino carrasco en Túnez El pino carrasco muestra una gran cobertura forestal, tanto en el norte de África como en toda la Cuenca Mediterránea, cuyo manejo no está totalmente desarrollado lo que requiere nuevas herramientas de manejo. En esta investigación, se estudiaron la estructura forestal, las características epidométricas y las relaciones alométricas de 79 parcelas distribuidas a lo largo de cuatro zonas bioclimáticas en bosques regulares de pino carrasco situados entre el este de Argelia y la costa este de Túnez. Para caracterizar la estructura forestal se aplicaron tres métodos de muestreo: inventario clásico (midiendo todos los pies) y dos propuestas más sencillas, usando un árbol medio o cinco pies dominantes por parcela. El análisis de varianza no mostraba diferencias significativas de las mediciones de diámetro de tronco y de copa realizadas entre las distintas zonas bioclimáticas usando ambos métodos. Por otra parte, se observó una disminución significativa de las zonas más húmedas a las más secas en altura toral, altura de copa y producción de semillas fue observada aplicando el método de árbol medio. Además, el análisis de covarianzas mostraba diferencias significativas, usando ambas metodologías, en los valores medios de altura total, diámetro de tronco y cobertura de...