Structural changes in Psidium guajava 'Paluma' leaves exposed to tropospheric ozone

Abstract

Structural changes in ABSTRACT(Structural changes in Psidium guajava 'Paluma' leaves exposed to tropospheric ozone). Psidium guajava 'Paluma' has being tested as an ozone (O 3 ) bioindicator and responds with pigmentation between the veins on the adaxial surface, due to the accumulation of phenolic compounds. Th ese compounds act as non-enzymatic antioxidants that neutralize reactive oxygen species (ROS), formed from O 3 . Th is study aimed to evaluate the leaf structure of plants with and without visible symptoms and to establish these symptoms at the cellular level. Beside this we also aimed to detect structural changes that can minimize the eff ects of the O 3 on the plant. Th e accumulation of phenolic substances, stomatal density and structural changes in P. guajava 'Paluma' leaf tissues exposed during the four seasons of the year were evaluated. Th e study was conducted at the Parque Estadual das Fontes do Ipiranga ( PEFI), which is a park in the city of São Paulo that has high levels of O 3 . Leaves with symptoms showed, on the adaxial surface, anthocyanin accumulation in the vacuoles of epidermal cells and hypodermis. When the symptoms were more intense this accumulation was observed even in the fi rst three layers of palisade parenchyma. Comparing symptomatic and asymptomatic leaves, there was higher accumulation of phenolic compounds in the symptomatic leaves. Some parenchyma cells adjacent to substomatal chambers showed intrusive growth towards the stomatal pore, promoting its occlusion, which could reduce the entry of O 3 in the leaf. Th e accumulation of anthocyanins and other phenolic compounds, in addition to the occlusion of the chamber, protect the plant against O 3 eff ects. Th ese features and the compact arrangement of the mesophyll contribute to why Psidium guajava 'Paluma' does not present cell death, a symptom usually observed in species sensitive to O 3 .

Discussões sobre os aspectos educacionais no Brasil (3a Edição)

“…As the storage period and the maturation process progressed, the anomalies started to become more noticeable, but restricted to the fruit epicarp. Similar symptoms were described by several researchers (FURLAN et al, 2007PINA & MORAES, 2007TRESMONDI & ALVES, 2011) when reporting the effect of ozone in 'Paluma'…”

Influence of post-harvest ozone application on the Epicarp of 'Pedro Sato' guava fruits under storage conditions

“…As the storage period and the maturation process progressed, the anomalies started to become more noticeable, but restricted to the fruit epicarp. Similar symptoms were described by several researchers (FURLAN et al, 2007PINA & MORAES, 2007TRESMONDI & ALVES, 2011) when reporting the effect of ozone in 'Paluma' and 'Pedro Sato' guava fruits (MORAES et al, 2011). Therefore, the anomalies observed in the present study are in accordance with the standard found in the literature (SÁNCHES et al, 2002;NOVAK et al, 2003).…”

Aprimoramento Do Ensaio Fitotoxicológico Com Germinação De Sementes De Alface: Confiabilidade E Acurácea Do Método

“…As the storage period and the maturation process progressed, the anomalies started to become more noticeable, but restricted to the fruit epicarp. Similar symptoms were described by several researchers (FURLAN et al, 2007PINA & MORAES, 2007TRESMONDI & ALVES, 2011) when reporting the effect of ozone in 'Paluma' and 'Pedro Sato' guava fruits (MORAES et al, 2011). Therefore, the anomalies observed in the present study are in accordance with the standard found in the literature (SÁNCHES et al, 2002;NOVAK et al, 2003).…”