Accumulation of micropolystyrenes in onion roots. Credit: Sukhendu Maity
Rising temperatures and salinity boost the accumulation of polystyrene nanoparticles in onion roots by increasing the activity of specific membrane proteins1.
This generates reactive oxygen species and destabilises microtubules essential for cellular structures and growth. Researchers at the Presidency University in Kolkata say such changes can slow plant growth and cause crop loss threatening food security.
Until now, how environmental stressors influence microplastic accumulation in plants has not been clear. To find out more, scientists led by Kousik Pramanick grew onion roots in sand from bulbs. The 2cm roots were exposed separately to microplastics, temperature stress plus microplastics and microplastic-laden saline water.
The team, which included researcher Sukhendu Maity, tagged the plastic particles with a light-emitting dye to track how they entered the roots.
The roots exposed to temperature stress accumulated more microplastics than those exposed to saline water. Heat stress increases the concentration of calcium ions in root cells. This opens aquaporins – membrane-based protein channels – allowing the plastic particles to enter.
The researchers found that exposure to heat stress also enhanced the expression of aquaporin genes but sodium azide blocks aquaporin activity and reduces the microplastics’ access. This suggests that aquaporins under heat stress facilitate the transport of plastic nanoparticles into onion roots, says Pramanick.
