Hilda Hildebrand Soriani

Effects of zinc addition to a copper-contaminated vineyard soil on sorption of Zn by soil and plant physiological responses.

The occurrence of high levels of Cu in vineyard soils is often the result of intensive use of fungicides for the preventive control of foliar diseases and can cause toxicity to plants. Nowadays many grape growers in Southern Brazil have replaced Cu-based with Zn-based products. The aim of the study was to evaluate whether the increase in Zn concentration in a soil with high Cu contents can interfere with the dynamics of these elements, and if this increase in Zn may cause toxicity to maize (Zea mays L.). Soil samples were collected in two areas, one in a vineyard with more than 30 years of cultivation and high concentration of Cu and the other on a natural grassland area adjacent to the vineyard. Different doses of Cu and Zn were added to the soil, and the adsorption isotherms were built following the Langmuirs model. In a second experiment, the vineyard soil was spiked with different Zn concentrations (0, 30, 60, 90, 180, and 270mg Zn kg(-1)) in 3kg pots where maize was grown in a greenhouse for 35 days. When Cu and Zn were added together, there was a reduction in the quantities adsorbed, especially for Zn. Zn addition decreased the total plant dry matter and specific leaf mass. Furthermore, with the increase in the activity of catalase, an activation of the antioxidant system was observed. However, the system was not sufficiently effective to reverse the stress levels imposed on soil, especially in plants grown in the highest doses of Zn. At doses higher than 90Znmgkg(-1) in the Cu-contaminated vineyard soil, maize plants were no longer able to activate the protection mechanism and suffered from metal stress, resulting in suppressed dry matter yields due to impaired functioning of the photosynthetic apparatus and changes in the enzymatic activity of plants. Replacement of Cu- by Zn-based fungicides to avoid Cu toxicity has resulted in soil vineyards contaminated with these metals and damaging of plant photosynthetic apparatus and enzyme activity.

Germinação in vitro de sementes e parâmetros morfofisiológicos de microestacas de Tabernaemontana catharinensis A. DC.

The aim of this study was to evaluate in vitro seed germination and the morphophysiological parameters of Tabernaemontana catharinensis microcuttings. In the germination bioassays, the seeds were immersed at solutions of 0.0; 300; and 600 mg L-1 GA3 for 24 or 48h. The seedlings from in vitro germination were used to produce microcuttings, which were inoculated in MS growth medium supplemented with 0.0; 1.0; 2.0; and 4.0 mg L-1 of IBA. The use of GA3 did not lead to higher seed germination rates in T. catharinensis and the germination rate was negatively aff ected in seeds exposed to GA3 for longer periods (48h). Rhizogenesis of T. catharinensis microcuttings can be induced without the need for phytoregulators. However, the morphophysiological parameters can be improved with the addition of IBA to the growth medium, showing that the use of IBA potentiates the production of aseptic microcuttings of T. catharinensis.

PROPAGAÇÃO IN VITRO DE Casearia sylvestris SWARTZ (SALICACEAE)

In order to do an in vitro propagation of Casearia sylvestris , a tree native to Brazilian forests, studies of in vitro seed germination were performed and aseptic seedlings obtained were used as explant donors for micropropagation. Mature and immature seeds, stored for 10 days at 10 or 25°C were inoculated in medium containing 10% of MS salts and kept in the light (a 16-hour photoperiod) or continuous dark, at 25°C. For immature seeds, gibberellic acid (GA 3 ) was or was not tested at a concentration of 1.5 mg l -1 . From the seedlings obtained, the cotyledon and apical segments were removed and cultured in complete MS medium with five combinations of 6-benzylaminopurine (BAP) and naphthalene acetic acid (NAA): 0.0; 0.25; 0.5; 1.0; 2.0 and 0.0; 0025; 0.05; 0.1; 0.2 mg L-1, respectively. The aerial shoots formed in vitro were cultured in MS medium containing 0.0 or 1.5 mg L -1 indole-3-butyric acid (IBA) for rooting. The highest percentage of germination (60%) occurred in mature seeds exposed to light, regardless of other treatments, and may be considered positive photoblastic. The highest percentage of germination of immature seeds (27%) occurred when previously stored at 10 ° C with or without GA 3 . The induction of aerial shoots was more efficient in apical segments in a medium containing the lowest combination of BAP and NAA or free of these growth regulators. The higher number of roots occurred in aerial shoots obtained from cotyledon segments, with or without IBA. After acclimatization, 83% of the plants survived.