Determination of cardinal temperatures of Birjandian aster (Mastar, Sclorhachis leptoclada Rech.f) and its phenological study in natural habitat

n order to investigate the phenological characteristics of Mastar (Sclorhachis leptoclada Rech.f) in natural habitat and to determine its cardinal germination temperatures, the study was conducted in 2018 in one of its natural habitats in South Khorasan province located in Ark protected area in in Research Laboratory of Islamic Azad University of Birjand. Treatments were seven treatments consisting of temperatures of 2, 5, 10, 15, 20, 25 and 30 °C with four replications in a completely randomized design. Measured traits included germination percentage and rate, average germination time, length and fresh weight of radicle and plumule and dry weight of seedling. Results of ecological study of the habitat showed that the habitat was mountainous and rocky with sandy soil and acidity of 8.18 with an average annual rainfall of 150 to 200 mm. The study of phenological stages of Mastar plant also showed that this plant needs 138 days and 1393.6oC during the growth stages. Regression analysis of seed germination data showed that, minimum, optimal and maximum germination temperatures were determined at 5, 10 and 30 °C, respectively.