Desempenho ecofisiológico de Syzygium jambos (L.) Alston, espécie exótica invasora cultivada sob diferentes substratos e intensidades luminosas

Abstract

Syzygium jambos (L.) Alston is a species of the Myrtaceae family, popularly known as “rose-apple” and originated in tropical Asia. It has great phenotypic plasticity to contrasting environmental conditions and high invasiveness, being able to adapt to both open areas as closed canopy. Its individuals form a dense crown, preventing colonization of native plants and the establishment of more light dependent species. It is therefore of great ecological importance. Despite being an invasive species in many tropical oceanic islands and continental areas, works aimed at understanding the ecophysiological mechanisms underlying this capacity are scarce. Thus, this study aimed to describe the morphological, biochemical and metabolic alterations in S. jambos plants grown under different light conditions and fertilization systems, and verify the feasibility of using the SPAD-502 chlorophyll meter in indirect determination of the levels of leaf photosynthetic pigments. For that, seeds were collected from one individual established in the Institute of Biological Sciences of UFJF and placed to germinate, during which the mobilization of cotyledon carbohydrates was assessed. The seeds were planted in plastic cups, and after raising to about 11 cm they were transplanted into pots of 25 L, filled with substrate formed by land and sand (control), substrate added with bovine manure and a third with the addition of chemical fertilizer. The plants were transferred to different light environments, called low radiation (BR), intermediate radiation (RI) and high radiation (AR), where they stood for about 10 months. The results of this study showed significant adaptive responses of S. jambos plants to different light environments, such as lower development of the aerial part, higher allocation of biomass in the roots, shorter internodes and the presence of leaves in a more vertical position in plants at full sun. In turn, plants under low radiation showed leaves with larger areas than plants under higher light intensities, in addition to significantly higher levels of photosynthetic pigments. There was a significant positive correlation between the levels of photosynthetic pigments measured spectrophotometrically and the SPAD indices, obtained with the help of chlorophyll meter, validating its use in indirect quantification of these levels in S. jambos plants. Regarding the antioxidative metabolism, there were different strategies to combat the formation of reactive oxygen species. Overall, the study highlights the increased activity of antioxidant enzymes in shadier environments, as well as increased production of carotenoids in the leaves developed in full sun. The photosynthetic and fluorescence parameters showed significant responses to changes in light condition. Regardless of the ambient light, plants of S. jambos showed growth and development while remaining viable. The present data allow us to conclude that the morphological, physiological and biochemical attributes presented by the invasive species Syzygium jambos in contrasting light conditions are of great importance for their acclimation and permanence in different natural environments, contributing to its invasiveness.