Tolerance to heavy metal stress in seedlings of three pine species from contrasting environmental conditions in Chile

Abstract

Tolerance to metal stress was studied in seedlings of three pine species (Pinus radiata, P. pinaster and P. canariensis) under controlled ex vitro conditions. Mature female cones were randomly collected at two sites in Chile (Llico and Huilquilemu) characterized by contrasting environmental conditions. One-year-old pine seedlings were immersed in trays with solutions of CuSO4 (300 mM) or AlCl3 (100 mM), and their survival, growth rate and decay symptoms were recorded for 60 days. Results showed large differences among provenances in seedling tolerance to CuSO4 and AlCl3 in terms of survival and growth. Multivariate analysis revealed a significant association (p <0.0001) between the first canonical function and the following variables: provenance, species, metal stress and growing rate, as well as between the second canonical function and provenance, species, metal stress and symptomatology, indicating a high degree of genotype-environment interaction. Moreover, the activity of POX, SOD and CAT enzymes was determined 60 days after the beginning of the experiment in the Llico provenance seedlings. P. pinaster showed the highest activity level for all the enzymes considered, while P. canariensis and P. radiata had intermediate and lowest values, respectively. Differential gene expression among pine seedlings under metal stress with CuSO4 for two genes (Cu-Zn-superoxide dismutase and RuBisCo) confirmed P. pinaster as the most tolerant species to CuSO4 treatment. Our results are consistent with the hypothesis that abiotic stress in the maternal environment can induce a “transgenerational plasticity” which could affect progeny performances. The influence of different genetic backgrounds on the tolerance to heavy metals in pine seedlings is also discussed.

Keywords

• Pinus spp.
• Heavy Metals
• Abiotic Stresses
• Genotype-Environment Interaction