Histology of maize seeds and young germinating embryos after liquid nitrogen exposure

Abstract

Maize represents a staple food crop and is the second most important agricultural commodity globally. Considering the important role of maize for food security, the long-term conservation of valuable germplasm is critical to ensure that high levels of genetic diversity are available for breeding superior cultivars to face future challenges. Cryopreservation is regarded as the most appropriate tool for long-term germplasm preservation and has been investigated in different crops. This short communication adds to the existing knowledge on maize cryopreservation by describing histological changes observed in maize seeds and young germinating embryos after liquid nitrogen (LN) exposure. Plants were examined immediately after recovery from LN (day zero) and following 3 days of germination. At day 3, seeds exposed to LN showed lower germination rates than non-cryostored seeds, i.e., 60.7% vs. 83.3%. Histological evaluation at day 3 revealed that the thickness of the conical endosperm and the scutellum did not show any statistically significant differences between control and cryopreserved seeds. In contrast, for the other histological evaluations made, mostly regarding the thickness of mesocarp, mealy endosperm, plumule, radicle and the epidermis, significant differences were observed between control and cryostored seeds with the former consistently displaying higher average values than the latter.