Two Iranian Scrophularia striata Boiss. Ecotypes under UV-B radiation: Germination and initial growth perspective

Concerning the increasing level of ultraviolet (UV) radiation in many parts of the world, researching plant establishment under UV exposure is an essential subject. This experiment was aimed at exploring the effects of UV-B on the germination rate, seedling length, radix and stem's length, seedling's fresh/dry weight, and germination indices of Scrophularia striata seeds (Scrophulariaceae), a native medicinal plant from Iran. Treatments included UV-B exposure times (0/control, 15, 30, and 45 min) on two different ecotypes of S. striata including Lizan (LE) and Pahleh (PE). The UV-B radiation treatment for 45 min significantly enhanced the final germination percentage (FGP) of PE seeds. Maximum TSG (time spread of germination) was achieved under 45 min UV exposure (3.67 Day) in PE, while in LE, increasing radiation caused a significant reduction in TSG. Regarding principle component analysis, PE showed better germination indices under UV-B radiation. The seedling length of S. striata was remarkably changed by UV-B treatment; in this case, enhanced seedling length was observed in LE than PE. The UV-B exposure can have promotive effects on many important germination indices in seeds and some seedling growth parameters in S. striata ecotypes, and this effect could be related to the ecotype differences and ecotype-specific responses.