Interactive effects of excess boron and salinity on histological and ultrastructural leaves of Zea mays amylacea from the Lluta Valley (Arica-Chile)

Maize is widely cultivated throughout the world, and more maize is produced each year than any other grain. Studies on the response of maize to salinity have typically focused on physiological aspects, but few studies have addressed the effects of salinity on the anatomical and ultrastructural characteristics of different plant organs. We analyzed the cell structure and changes in tissue organization in young leaves of Zea mays L. amylacea as a consequence of high salt and boron (B) levels. Plants were treated in nutrient solutions for 20 days with concentrations of 100 mM NaCl (Low salinity, L) or 430 mM NaCl (High salinity, H) in the case of saline treatments or with an excess of B supplied as boric acid to obtain 20 mg (334 μM) or 40 mg (668 μM) B kg-1. The application of B under no salt and low salinity conditions did not result in ultrastructure changes in mesophyll cells (MC) or bundle sheath cells (BSC). The high salinity conditions the amylacea leaf cells showed some alterations in MC chloroplasts, which appeared swollen and rounded. The BSC chloroplasts lost their perpendicular disposition to the cell wall. Moreover, the absolute absence of plastoglobuli could indicate a greater resistance to oxidative damage.