Desempenho ecofisiológico de mudas clonais de Eucalyptus urograndis GG680 submetidas a diferentes concentrações salinas

Abstract

Eucalyptus has played an important role in reforestation programs in Brazil, and for the supply of wood, especially for the pulp and steel industry, standing out for its advantages over other cultivated forest species. The soil salinization process comes from environmental and/or anthropogenic characteristics, where they affect crop yields and affect the chemical and physical characteristics of the soil. In arid and semi-arid regions, low rainfall and high evapotranspiration rates accelerate the salinization process in these areas. Based on the above, this study aimed to evaluate the ecophysiological behavior of Eucalyptus urograndis GG680 seedlings submitted to different levels of saline concentration, in order to determine the point at which salinity begins to impair their initial development. The work was conducted at the Production Technology Laboratory (LATEP) - Silviculture and Forest Nursery Sector, located at the Campus of Engineering and Agrarian Sciences (CECA), of the Federal University of Alagoas (UFAL). The experimental design was adopted in randomized blocks, containing four saline treatments and one control (without the addition of salt – 0 (Control), 50, 100, 150 and 200 mM). For each of these treatments, five replicates were assigned. At the end of the experimental period, the leaf area, membrane integrity (absolute percentage, relative percentage and percentage of membrane damage), photosynthetic pigments (Chlorophylls a, b, total and carotenoids), as well as the dry matter production of the following organs were evaluated: leaf, stem, root system, total and root/shoot ratio. In the analysis of leaf area, specific leaf area and leaf area ratio, there was a reduction in the increase in salinity. The percentage of absolute integrity was compromised with the saline dosages. In the same way that the percentage of relative integrity and membrane damage increased with salt. Chlorophyll pigments a and b presented the lowest mean in the 200 mM treatment. Regarding leaf dry matter production, the 200 mM treatment presented the lowest average, and the highest for root/shoot ratio. When analyzing the biomass allocation, it was found that the root was the one that obtained the highest production within all treatments. Finally, allocation was performed between the treatments. Among the variables studied, it was found that the evaluation of the quantities involved with membrane damage, leaf area and specific leaf area are good indicators of sensitivity in clonal seedlings of Eucalyptus urograndis GG680 when submitted to regions affected by salinity. While the 200 mM concentration of NaCl was harmful in all the analyses performed in this study. This research allowed us to infer that clonal seedlings of Eucalyptus urograndis GG680 begin to show symptoms of salt toxicity from 100 mM, and it is recommended to plant them in soils that have salinity below these levels.