Structural and ultra-structural analysis of Conocarpus erectus pollen grains before and after dust storms

Abstract

Ahvaz city in Iran was designated as the most polluted city in the world in 2013 that suffered from a lot of dust storms. Conocarpus erectus is currently the dominant tree species in Ahvaz. In this study, ripe and young inflorescences of plants grown in three cities of the Khuzestan province on dust storm days and clean days (days with no dust storm) were selected and the stamina were separated. Pollen grains were checked in a scanning electron microscope and analysis of the elements existing on the surface of the anthers and pollen grains was accomplished using energy-dispersive X-ray spectroscopy. Results showed that the pollen grains are small-sized monads and the mature pollen has six lobes in a polar view and has six heterocolpate apertures (three colpates and three colporates, one alternating the other) with a polar axis length (P) of 12.998 ± 1.516 μm and an equatorial axis length (E) of 8.698 ± 0.557 μm. The dense Calcite crystals (CaCO3) and particulate matters smaller than 2.5 μm in size including the fragments containing elements such as aluminium, silicon and iron, which are components of soils were attached to all parts of those pollen grains which were collected after dust storms. The crushed pieces of calcite crystals were also seen in the pollen apertures.