The cortex often develops into a type of tissue called aerenchyma, which contains air spaces produced by separation, tearing, or dissolution of the cortex cell walls.
Aerenchyma is an airy tissue found in roots of plants, which allows exchange of gases between the shoot and the root. It contains large air-filled cavities, which provide a low-resistance internal pathway for the exchange of gases such as oxygen and ethylene between the plant parts above the water and the submerged tissues.
This permits the plants to grow without incurring the metabolic costs of anaerobic respiration. Some of the oxygen transported through the aerenchyma escapes through root pores into the surrounding soil.
The resulting small rhizospheres of oxygenated soil around individual roots support the microorganisms that avoid the influx of possibly toxic soil components such as sulfide, iron, and manganese.
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