Avaliação do uso de ácido salicílico em sementes de calêndula (Calendula officinalis L.) sob diferentes estresses

Abstract

Marigold (Calendula officinalis L.) is an important medicinal and decorative plant also used in the kitchens and in the manufacturing of cosmetic and phytotherapic products. Plants are susceptible to biotical and non biotical aggression and independently of not showing agile movements as defence; they could present deep modifications in the cell metabolism as defence protein synthesis activated by single molecules or complex mechanisms. The exogenous application or the synthesis stimulus of organic acids as salicylic, may act as an inductor of tolerance protein to different biotical or non biotical stress increasing the detoxification enzyme activity, specially those ones involved in the degradation of reactive oxygen species. The aim of this work was the study of salicylic acid (SA) over the germination and vigour of marigold seeds (Calendula officinalis L.) in ideal or stressing conditions. Seeds were put to germinate in paper wetted with SA (zero, 0.0125, 0.025, 0.05, 0.1 and 0.2mM). Germination (G%), first germination counting(PC) and germination velocity index (IVG) were measured. Just germination was significant, and the best doses were 0.025 and 0.05 mM of SA. Three other experiments were done one with acid water, adjusted to the pH of the related SA solutions (6.0; 4.8, 4.2 3.6 and 3.2), one with different water potentials, induced by mannitol (0; -0.3; -0.6; -0.9 and -1.2 MPa) and one with different temperatures(20, 25, 30 e 35ºC). pH had no effect over germination and IVG of Marigold seeds, so the effect observed earlier was due to SA. The treatment with 0.025mM of SA increased the G% and IVG of marigold seeds exposed to water deficit. Temperature with or without SA treatment were superior at 20ºC than the recommended temperature of 25ºC.