The sensitivity of radish cultivars to high temperatures during germination and seedling growth stages

A laboratory experiment was conducted at constant temperatures of 20, 23, 26, 29, 32, 35, 38, and 41℃ to identify the response of six radish cultivars with different root sizes and colors to high-temperature stress during germination, emergence, and early seedling growth stage. Also, the optimal temperature was determined by calculating the relationship between seedling length and temperature via a polynomial regression model. The results showed that no seed germination was detected at 41℃, while emergence and seedling growth were not observed at 38℃ and above. Similar germination percentages, mean germination time, and germination index were obtained between 20℃ and 35℃. The root length reduced at 32℃ and it was more sensitive to high temperatures than shoots because the root/shoot length ratio showed a decreasing trend by increasing temperatures and longer root length was recorded at lower temperatures than 32℃. There were genotypic variations among radish cultivars for temperatures and ‘Kırmızı İnci’, ‘Beyaz İnci’, and ‘Siyah İnci’ produced a better performance than the others under high temperatures. The regression analysis predicted the optimal temperatures as 21.5℃ and 22.6℃ for root and shoot length, respectively. This study indicates that high temperatures inhibited seedling growth rather than seed germination performance of radishes.