Name: Rosiane Cipriano
Type: PhD thesis
Publication date: 26/08/2022
Advisor:
Name |
Role |
|---|---|
| Antelmo Ralph Falqueto | Advisor * |
| João Paulo Rodrigues Martins | Co-advisor * |
Examining board:
| Name |
Role |
|---|---|
| Antelmo Ralph Falqueto | Advisor * |
| Camilla Rozindo Dias Milanez | Internal Examiner * |
| Diolina Moura Silva | Internal Examiner * |
| Eugenia Jacira Bolacel Braga | External Examiner * |
| Geraldo Rogério Faustini Cuzzuol | Internal Alternate * |
| Luiz Carlos de Almeida Rodrigues | External Alternate * |
| Wagner Campos Otoni | External Examiner * |
Summary: Plants are exposed to frequent sources of abiotic stresses such as high salinity and trace elements, including cadmium (Cd). The use of silicon (Si) is an alternative that can alleviate the deleterious effects of these stresses. The first manuscript (chapter 1) aimed to analyze the influence of different sources and concentrations of Si on anatomical responses and on the effective photochemical activity of photosystem II (PSII) in Aechmea blanchetiana plants under in vitro conditions. The second manuscript (chapter 2) evaluated the effect of saline stress in vitro and the mitigating
potential of Si in A. blanchetiana plants. The third manuscript (chapter 3) investigated the anatomical and physiological modulations of A. blanchetiana exposed to Cd in vitro and co-exposure to Cd and Si. In the first experiment lateral shoots of plants previously established in vitro were transferred to culture medium. Media without Si were used as
a control. The treatments consisted of calcium silicate (CaSiO3), potassium silicate (K2O3Si) and magnesium silicate (MgO3Si) in three concentrations (8, 16, 32 μM). After 45 days of cultivation, anatomical and physiological analyzes were performed. The study proved that Si increased xylem vessel diameter, phloem area and plant growth. Among the Si sources tested, CaSiO3 was the one that presented the greatest contribution to increase the effective functioning of PSII and plant growth. In the second experiment, plants already established in vitro were transferred to a culture medium
with 0 or 14 µM of Si (CaSiO3). After 30 days of growth, stationary liquid medium containing different concentrations of NaCl (0, 100, 200 or 300 µM) was added to the flasks. After 45 days, anatomical and physiological analyzes were performed. Plants grown with excess NaCl showed a reduction in the effective photochemical quantum yield of PSII and an increase in the non-photochemical dissipation of fluorescence. Plants in the presence of Si had an increase in the content of photosynthetic pigments, in the activity of enzymes of the antioxidant system and in the coefficient of
photochemical fluorescence dissipation (qP). Anatomical, physiological and biochemical responses induced by Si had a mitigating effect of saline stress in A. blanchetiana cultivated in vitro. In the third experiment, plants previously established in vitro were transferred to a culture medium with 0 or 14 μM of Si. After 30 days of growth, stationary liquid MS medium containing increasing concentrations of Cd (0, 50, 100 or 200 μM) was added to the containers. After 45 days, anatomical and physiological analyzes were performed. Plants grown with Si showed a thinner exoderm, decreased concentration of Chl a/b and higher total Chl/Car ratio. Cd induced damage to the oxygen-evolution complex (WK) and altered the quantum yield of nonregulated energy dissipation (ΦNO). In the presence of Si there was an increase in the
photochemical activity of PSII and electron transport, even when the plants were exposed to Cd. Anatomical and physiological responses induced by Si were effective in easing the stress of A. blanchetiana plants grown in vitro with Cd.
