Impact of liquid nitrogen exposure on selected biochemical and structural parameters of hydrated Phaseolus vulgaris L. seeds

BACKGROUND: It is well known that cryopreserving seeds with high water content is detrimental to survival, but biochemical and structural parameters of cryostored hydrated common bean seeds have not been published. OBJECTIVE: The objective of this work was to study the effect of liquid nitrogen exposure on selected biochemical and structural parameters of hydrated Phaseolus vulgaris seeds. MATERIALS AND METHODS: We cryopreserved seeds at various moisture contents and evaluated: germination; electrolyte leakage; fresh seed weight; levels of chlorophyll pigments, malondialdehyde, other aldehydes, phenolics and proteins; thickness of cotyledon epidermis, parenchyma, and starch storage parenchyma; and radicle and plumule lengths. RESULTS: Germination was totally inhibited when seeds were immersed in water for 50 min (moisture content of 38%, FW basis) before cryopreservation. The combined effects of seed water imbibition and cryostorage decreased phenolics (free, cell wall-linked, total), chlorophyll a and protein content. By contrast, electrolyte leakage and levels of chlorophyll b and other aldehydes increased as a result of the combination of these two experimental factors. These were the most significant effects observed during exposure of humid seed to liquid nitrogen. CONCLUSION: Further studies are still required to clarify the molecular events taking place in plant cells during eryostorage