Efeito do gás sulfídrico na formação de tricomas e na resposta das variedades de solanum lycopersicum micro-tom e MT-GET à injúria mecânica

Abstract

Trichomes are structures responsible for the production of a variety of secondary metabolites that are implicated in plant response to herbivory. Hydrogen sulfide (H2S) is a gas that has emerged as a signaling molecule during plant growth and development and in response to stress. This work focused on the investigation of the effect of an H2S donor (Na2S) under two pH conditions on the trichome formation in Solanum lycopersicum cv. Micro-Tom (MT) and the hybrid Get. Plants bearing the first fully expanded leaf pair were sprayed with Na2S at 0, 50, 100 or 200 M (pH 11.0) for 15 days. In another experiment, mechanical stress was imposed in plant leaves followed by treatment with 100 M Na2S (pH 6.4). Plant growth and leaf production were not affected by the treatments. The number of trichomes on the adaxial face of young leaves treated with Na2S (pH 11.0) was 30% lower than that of young leaves of control plants, regardless of the genotype. However, the use of Na2S (pH 6.4) promoted trichome formation on adaxial face of MT and Get young leaves by 80% and 48%, respectively. This treatment also stimulated theincrement of glandular trichome proportion in both genotypes. Mechanical damage is known to cause oxidative stress and induce trichome formation in new leaves. However, this damage neither affected the number of trichomes nor the H2O2 content in young leaves after 21 days of treatment. The treatment with Na2S (pH 6.4) reestablished the activity of superoxide dismutase to control levels in MT injured plants. Application of Na2S at pH 11.0 may have changed the pH of the leaves and this alteration may have culminated in the inhibition and/or delay of trichomes formation in young leaves. Thus, the pH of H2S donor solution was found to be pivotal for the actual effects of this signaling molecule in plants. The H2S signals cellular processes that, in turn, may trigger the induction of trichome formation in young leaves of tomato plants.