Jan Kubiś

The effects of short-term 48 h long NaCl-stress and spermidine level modification on polyamines level and antioxidant status in cucumber (Cucumis sativus cv. Dar) leaves were investigated. Seedlings kept in nutrient solutions treated with 50 mM NaCl for 48 h exhibited reduced relative water content and accumulation of free polyamines, especially spermidine. Salinity stress caused an increase in superoxide radicals and hydrogen peroxide generation during the salinity-induced increase in antioxidant enzyme activities. Spermidine application before stress resulted in a marked increase in spermidine and spermine contents in the leaves of salt-stressed cucumber seedlings. Additionally, increased spermidine/spermine level mobilised the antioxidant enzyme’s activity and limited reactive oxygen species content. Polyamine synthesis inhibitor (MGBG) slightly decreased spermidine and spermine levels during salinity and reversed the antioxidant activity mobilisation. These results showed that Spd modifications significantly improved PAs, enhancing salinity stress tolerance by detoxifying ROS. Our findings determined the implication of PAs for improving the salinity tolerance of important vegetable species.

Two cultivars of Heuchera L. - ‘Mysteria’ and ‘Peppermint Spice’ were grown in a collection at a sunny site and a slightly shaded one. The access of sunlight was limited by shade nets, which were stretched on wooden scaffolding over the plants. The dynamics of growth of the plants in the sunny and half-shaded sites was assessed in the growth periods, in two consecutive years. After the second year, the content of anthocyanins in the leaves of different physiological maturity (young, mature and fully mature) was measured. Apart from August, during the whole growth period both cultivars formed more leaves during the first year of cultivation. Both the ‘Mysteria’ and ‘Peppermint Spice’ cultivars formed more leaves at the sunny site. The research showed that the highest content of anthocyanins in the Heuchera ‘Mysteria’ and ‘Peppermint Spice’ cultivars growing at the sunny and half-shaded sites was found in young leaves, whereas the lowest content was noted in fully mature leaves. The highest content of anthocyanins in both Heuchera cultivars was found at the initial growth period, i.e. between May and July, when the light intensity was the greatest, regardless of the place of cultivation. At the end of the growth period, the biosynthesis of anthocyanins decreased significantly. Anthocyanins accumulated in the vacuole are able to play a role as the screening pigments under intensive PAR and UV-B radiation. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********