Enhancement of maize seed viability after cold storage and induced senescence by priming with synthetic cytokinins

Maize (Zea mays L.) plants were treated with synthetic cytokinins - 6-benzylaminopurine (BAP) and 6furfurylaminopurine, or kinetin (KIN) - during the grain filling stage in a field experiment performed in 2020 in Sadovo, central Bulgaria. The objective was to study their effect on plant productivity and seedling viability of maize after cold storage. The morpho-physiological parameters of the leaves assessed 15 days after cytokinin priming showed an increase in biosynthetic processes compared to control plants. Analysis of yield parameters at harvesting revealed improved productivity of cytokinin-treated plants, which was evidenced as 10 mg L-1 KIN, and BAP priming resulted in, respectively, 18% and 16% higher grain mass compared to untreated plants (control). The produced seeds were exposed to cold storage (-18 & DEG;C) for 12 months and afterwards physiological parameters of 5-day-old seedlings were measured to evaluate exogenous cytokinins' impact upon stress alleviation. The seedlings developed from cytokinin-treated plants accumulated significantly lower amounts of oxidative stress markers (hydrogen peroxide and malondialdehyde) after cold storage. In a laboratory experiment, maize seeds were subjected to artificially induced senescence (AIS) test for 72 h at 41 & DEG;C temperature and were subsequently soaked in cytokinin solutions. Cytokinins had a positive effect on both physiological parameters of seedlings of field-grown plants after cold storage and improved the performance of seedlings after AIS test through increased oxidative stress protection and enhanced reactive oxygen species (ROS) detoxification.