Cell membrane permeability and antioxidant activities in the rootstocks of <em>Miscanthus x giganteus</em> as an effect of cold and frost treatment

Abstract

The aim of the study was to estimate the ability of Miscanthus x giganteus to acquire frost tolerance. Field grown rootstocks were transferred into pots and cultivated in a glasshouse at 20°C. After 5 weeks plants were pre-hardened at 12°C for a further 2 weeks and then hardened at 5°C for another 3 weeks. After this time, plants were frozen at -8°C or -15°C for 1, 3 or 5 days, after which their regrowth at 20°C was investigated. The membrane permeability (electrolyte leakage), activity of the catalase (CAT), non-specific peroxidase (PX), and protein content in stolons were measured, before and after pre-hardening, as well as after hardening and freezing.
Both pre-hardening and hardening decreased membrane permeability of the rootstock cells, and this effect was observed further, after 5-week of regrowth at 20°C. Freezing at both temperatures increased ion leakage gradually over the period of treatment. On the basis of total ion content, damage to the cell membranes of frozen stolons after recovery was state. Prehardening increased CAT activity, while hardening did not alter it. However, after 5-week de-hardening, CAT activity decreased significantly. Freezing at -8°C for 5 days increased significantly the activity of this enzyme. At -15°C CAT activity was lower than in the control after only one day of freezing. PX activity decreased both in the rootstocks of cold (12°C and 5°C) and frost treated plants. Protein content increased significantly in the stolons of both pre-hardened and hardened plants, although not immediately after cold treatment, but only after a 5-week re-growth period in a glasshouse at 20°C. This phenomenon was observed also in the stolons of plants frozen at -15°C for 5 days. From frozen rootstocks no new stems in regrowth conditions were obtained. The results obtained indicated, that although frozen stolons cannot produce new shoots, they do demonstrate some metabolic vitality. So, it could be supposed that the frost susceptibility of studied plants resulted from the strong sensitivity of shoot apical meristems to the cold. Further studies will analyse the survival of Miscanthus in milder frost temperatures.