Air pollutants

Air pollutants are considered abiotic agents that cause non-infectious physiological diseases in plants. While they are not classified as living pathogens, their impact on plant health is profound, often acting as a predisposing factor that weakens plant defenses, thereby facilitating infection by secondary biological parasites such as fungi and bacteria.

Common air pollutants include ground-level ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NOx), and peroxyacetyl nitrates (PAN). These substances enter plant tissues primarily through stomata. Once inside, they induce oxidative stress, which leads to the destruction of the chlorophyll molecule and the impairment of essential photosynthetic pathways, effectively starving the plant.

The biology of the damage involves the disruption of cellular membranes and the inhibition of enzyme systems. This process manifests as visible injury symptoms, including interveinal chlorosis, bronze or silvery discoloration, and necrotic spotting. Because these symptoms resemble those of viral or fungal infections, accurate diagnosis requires analyzing environmental monitoring data alongside symptomatic inspection.

Conditions for development are heavily influenced by environmental factors such as solar radiation, air humidity, and temperature inversions. In urbanized or industrialized agricultural regions, these pollutants often accumulate near the ground. High metabolic activity in plants during rapid growth stages increases the intake of these toxic gases, making crops particularly vulnerable during the flowering and fruit-setting phases.

Effective management and protection strategies focus on increasing plant resilience and minimizing direct exposure. This includes monitoring air quality indexes, selecting tolerant cultivars with lower stomatal conductance, and applying specialized fertilizers that enhance the plant's antioxidant capacity. Maintaining soil health and irrigation management also plays a crucial role in mitigating the severity of pollution-induced stress.