Pollution Induced Leaf Morphoanatomical Changes of Quillaja saponaria in Santiago, Chile

Research Article

Austin Environ Sci. 2020; 5(1): 1041.

Pollution Induced Leaf Morphoanatomical Changes of Quillaja saponaria in Santiago, Chile

Egas C1, Bown H2, Godoy N3, Hernández HJ2, Naulin P2, Ponce M4 and Préndez M3*

1Instituto de Ciencias Biológicas, Universidad de Talca, Chile

2Facultad de Ciencias Forestales y Conservación de la Naturaleza, Universidad de Chile, Chile

3Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Chile

4Facultad de Ciencias Forestales, Universidad de Talca, Chile

*Corresponding author: Margarita Préndez, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingtone Polhammer 1007, Independencia, Santiago, Chile

Received: January 30, 2020; Accepted: February 24, 2020; Published: March 02, 2020


Particulate matter and ozone, which affect human and environmental health, are the atmospheric pollutants most frequently exceeding the national standards in Chilean cities. The objective of this work was to assess the effect of both pollutants on the native urban tree Quillaja saponaria Molina leaves. Batches of ten individuals of Q. saponaria were located close to nine official pollution monitoring stations, belonging to the Air Quality Monitoring Network of the Metropolitan Region of Santiago, Chile. Morpho-anatomical traits of Q. saponaria leaves were analyzed after twelve months of exposure to the environmental condition. There is a significant positive relationship between leaf area and particulate matter, while stomata width and palisade thickness decreased. Leaf traits were independent of ozone concentration. Therefore, particulate matter changed some morpho-anatomical traits, and affects the physiological functioning of the tree. These findings are important to take better decisions for urban planning and to improve the air quality of cities.

Keywords: Particulate matter; Ozone; Morpho-anatomical leaf traits; Quillaja saponaria; Santiago chile


One of the main problems affecting quality of life in urban cities is anthropogenic atmospheric pollution produced by atmospheric aerosols and particulate matter (i.e. mainly particulate matter of ≤2.5 and ≤10 μm in aerodynamic diameter, namely PM2.5 and PM10, respectively), inorganic and organic gaseous compounds. There is increasing awareness and concern about the negative effects of pollution on human health, ecosystems, visibility, infrastructure, as well as economic and social welfare. A direct relationship has been established by WHO between exposure to high concentrations of coarse and fine particles and the levels of mortality and morbidity of the population [1].

In several cities worldwide, the use of urban vegetation (trees, shrubs and grasses) has been integrated as part of programs, policies and measures for the reduction of pollutant concentration and for human health protection [2,3,4]. This reduction can occur directly by deposition on the tree surface and/or by stomatal uptake of atmospheric pollutants [5]. Plants exhibit a large foliage area per unit volume, increasing the probability of interception and deposition that varies substantially depending on particle size and leaf roughness [6]. Particle deposition can also be increased by the presence of epicuticular waxes in which become stuck or immersed [7,8].

Trees can grow in places with high levels of pollutant concentration and accumulate organic and inorganic chemical species in their cells. The response of each plant species to a particular type of pollutant is different depending on a set of environmental conditions [9,10]. Leaf functional traits are reliable markers that show significant variations between plants, as well as among different biotic and abiotic stressors [11].

Particulate matter contains solid and liquid particles of different origins, sizes, shapes and chemical composition that can cause diverse effects on plants and ecosystems [12]. The presence of PM on leaves has an adverse effect on plants, mainly by limiting the amount of light reaching the mesophyll, which is reflected, reducing the amount of absorbed photosynthetic active radiation [13,14]. The biological effects of PM deposited on the leaves may increase acidity, salinity, nutrient content, trace metal content and change surfactant properties of leaves [12].

Tropospheric ozone can also cause adverse effects on vegetation. The reactions of ozone and the internal components of leaves can lead to the formation of reactive oxygen species leading to oxidative stress and damage to plants [15]. As a strong oxidant, ozone causes several types of visible lesions including chlorosis and necrosis [16,17], affects the metabolic processes of the plant that leads to reduction of carbon assimilation [18], growth [19], foliar area [20] and stomatal control [21,22]. In addition, ozone pollution can induce programmed cell death, accelerate senescence and weaken the defense against pests and diseases [23-25].

Santiago (33 ° 26’16 “S 70 ° 39’01” W) is the capital city of Chile located in the Maipo river basin, in the central valley (400 to 1200 m asl), between the Andes to the east, and the Coastal mountains to the west. The population of Santiago is about 40.5% (7,112,808 inhabitants) of the country’s population [26]. Santiago shows high concentrations of PM and O3 which generates effects on the socioeconomic and environmental ecosystems. High PM concentration levels usually occur in the autumn-winter months mediated by poor ventilation conditions, sometimes producing critical episodes (concentrations 2-3 times over national quality standard). Anthropogenic emissions (volatile organic compounds and nitrogen oxides in the basin) generate ozone in the summer months [27]. In addition, population growth and urban expansion have replaced agricultural lands and natural habitats [28] negatively affecting the air quality, decreasing vegetation cover and increasing temperatures [29].

Models predict that urban vegetation, mainly trees, can reduce PM and some gases [30-32]. Experimental research shows that PM retention is species specific [33-35], having a beneficial effect on the population. However, the effect on morpho-anatomical traits of air pollution on plants has been less studied.

The aim of this work is to assess the effect of PM and ozone on morpho-anatomical traits of the native species Quillaja saponaria Molina. Hernández and Villaseñor [36] report that this a native evergreen tree with an abundance of 3.48% in the native urban green infrastructure of Santiago city (13.52%).

Materials and Method

Plant material

Pots of ten two-years-old plants (around 1.5 m tall) of Q. saponaria (QS) from the nursery of the Facultad de Ciencias Forestales y de la Conservación de la Naturaleza, Universidad de Chile, were located in November-December 2014 near (2-700 m) nine official Monitoring Stations (MS) within network for the Metropolitan Region of Santiago, Chile. Plants for this experiment originate from seeds of a single population and genetic background. For each station, random plants were selected that had the same initial size. The MS included in this study were (Table 1): Cerrillos (MS-C), Cerro Navia (MS-CN), El Bosque (MS-EB), Independencia (MS-I), Las Condes (MS-LC), La Florida (MS-LF), Puente Alto (MS-PA), Parque O’Higgins (MS-PO) and Quilicura (MS-Q), located between 481 masl (west) and 785 masl (east) [37]. From each individual plant, ten fully expanded leaves from the upper third of the upper canopy were harvested between November 2014 and January 2016. All plants were exposed to the environmental conditions of the corresponding monitoring station (temperature, humidity, radiation) and regular irrigation.