Néctar extrafloral em plantas de mandioca : um possível mecanismo de defesa induzida

Abstract

The extrafloral nectar (EFN) of some plants is generally associated with their indirect defense, attracting, and rewarding natural enemies (NE) that can protect the plant. Recent studies show that it is possible to induce defenses like EFN in a way that can be qualitatively evaluated, regarding the analysis of soluble solids concentration, through the application of artificial damage or phytohormones involved in plant defense regulation, such as cis-Jasmone or Methyl Jasmonate, increasing EFN concentration making it more valuable to NE, consequently making the plants more resistant to herbivory. In this study, was investigated how different methods of defense induction affect the EFN concentration in cassava. To do this, artificial damage was done to plants by cutting 50% of the leaves while keeping others intact as controls. In other group of plants, a solution of cis-Jasmone (concentration 1.43 mM), Tween 20 and distilled water was applied, while the controls received only Tween 20 and distilled water. Finally, a solution of Methyl Jasmonate (concentration 0.2 mM), Tween 20 and distilled water was applied, while the controls only received Tween 20 and distilled water. After 24 hours and 72 hours, the EFN was collected from these plants using glass capillaries, and the concentration of soluble solids was verified with a refractometer. After the collection of EFN, dry weighing of the plants was also conducted. Both exogenous applications of cis-Jasmone and Methyl Jasmonate altered the EFN concentration between the control plants and the treated plants. On the other hand, artificial damage showed no significant difference between the different treatments. It was also observed that the dry weight of the plants influenced on the quality of EFN. Therefore, under the conditions of this experiment, it is concluded that cis-Jasmone and Methyl Jasmonate were able to induce a more concentrated production of EFN in cassava plants. It is believed that the concentration of soluble solids in EFN is your main factor responsible for mediating the relationships between plants and NE. Therefore, these results imply the possibility of making plants more attractive to NE and consequently improving their defense with the application of these phytohormones, which could assist in the integrated pest management of cassava. However, additional studies on the relationship between EFN and NE and testing different treatment intensities or other induction methods, such as herbivory, are still necessary to better understand the qualitative induction of EFN in cassava.