Name: DAYANA EFFGEN FANTINATO
Type: PhD thesis
Publication date: 07/08/2018
Advisor:
Name |
Role |
|---|---|
| Camilla Rozindo Dias Milanez | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| Camilla Rozindo Dias Milanez | Advisor * |
| CARLOS ALBERTO SPAGGIARI DE SOUZA | External Examiner * |
| Geraldo Rogério Faustini Cuzzuol | Internal Alternate * |
| Gloria Maria de Farias Viégas Aquije | External Examiner * |
| LEONARDO VALANDRO ZANETTI | External Alternate * |
| Silvia Tamie Matsumoto | Internal Examiner * |
| Viviana Borges Corte | Internal Examiner * |
Summary: The cacao tree (Theobroma cacao) is a perennial species, of arboreal origin originating in the High Amazon region. The economic importance of this species is mainly related to its seeds, which are used for the manufacture of chocolate. Within the national scenario, Espírito Santo occupies the 4th position as the largest producer, and most of this production is in the municipality of Linhares. In Espírito Santo, the cultivation of cacao, which was shaded, has become, in recent years, predominantly in full sun. In this condition, the plants are more exposed to the action of winds. It is known that wind is characterized as an environmental variable that interferes with plant growth, however, little is known about its effects on the structural and physiological characteristics of cacao, influencing its development. In an attempt to ameliorate abiotic stresses, silicate fertilization has shown promise with positive effects on growth, gas exchange and biochemical defenses. In this context, the objective of the present work was to evaluate the influence of the wind through the analysis of gaseous changes, the morphoanatomic characteristics, lignin content and structural carbohydrates on cocoa seedlings. From the results, the effects of a possible action of the silicon in the reduction of the stresses caused by the wind were evaluated. For this, in a first experiment, seedlings of the genotype PS-1319 of T. cacao were used in two areas, one being totally exposed to the wind and the other consorted with banana trees, with lower wind incidence. Monthly growth analyzes were carried out in these plants for 12 months and at the end of this period, leaf anatomy, gas exchange, lignin content and structural carbohydrates were evaluated. In the second experiment, seedlings of the same genotype were grown in nurseries and submitted to silicon treatments, applied to the leaf and soil, at concentrations of 2 mM and 1 mM, respectively. Later, the seedlings were submitted to a wind source with an average velocity of 2.25 m / s, from 11 am to 6 pm, for 28 days. At the end of the experiment were performed growth analysis, foliar anatomy, lignin content and leaf structural carbohydrates, gas exchanges and enzymatic and biochemical analyzes. The results show that the plants more exposed to the wind presented higher density, stomatal conductance and greater photosynthesis. Anatomically, the leaves were thicker, presenting larger palisade and spongy parenchyma, greater abaxial and adaxial epidermis and greater lignification and central vein, which presented more fibers, allowing these plants to be more rigid. However, there was a reduction in growth. The evaluation of the effects of silicon on the plants subjected to the wind demonstrated that the silicate fertilization worked in a positive way promoting increase of the vein, with increase of the flolem and parenchymatic cells, and of the leaf area, leading to the maintenance of carbon assimilation. Silicon led to reduced transpiration and enzymatic activity of PPO, APX and SOD, providing energy savings.
