Optimization of seed germination and micropropagation of Althea rosea L. in vitro condition

The common hollyhock (Althea rosea) is a wild, annual plant. Its flowers, fruits and roots have medicinal properties. The cultivation of this medicinal plant is mostly challenged by a lack of proper seed germination and, as a result, an unfavorable establishment of seedlings in primary conditions of cultivation. Breaking the seed dormancy and stimulating seed germination in this species are known to have several ways. In three replications, this experiment was performed in a completely randomized design on three hollyhock ecotypes from Sepidan Shiraz, Kordan Karaj and Isfahan. In the first experiment, germination was evaluated after the seeds were exposed to 4 °C in different time periods (0, 10 hours, 7, 14, 21 and 28 days), while another treatment group involved the exposure of seeds to 35 and 46 °C in a steam bath for 6 hours. In the second experiment, the proliferation of hollyhock was optimized in vitro using a combination of different plant growth regulators, including 2 mg/L benzyl adenine (M4), 1 mg/L benzyl adenine in combination with 0.10 mg/L naphthalene acetic acid (M13), 1 mg/L thidiazuron (M6), 1.5 mg/L thidiazuron in combination with 0.10 mg/L naphthalene acetic acid (M17), 0.5 mg/L kinetin (M8), and 2 mg/L kinetin in combination with 0.10 mg/L naphthalene acetic acid (M20). The analysis of variance for the first experiment showed that the effect of ecotype (Sepidan Shiraz, Kordan Karaj and Isfahan) was significant (P≤0.05) on germination. This included the percentage and rate of germination, root volume and height of seedlings. The effect of temperature on seed germination was significant (P≤0.05), while also affecting other traits (P≤0.01). The highest values of proliferation, shoot length and rooting percentage were observed in the Shiraz ecotype when treated with M4 in vitro. The lowest values of these parameters were observed in the Karaj ecotype when treated with M20. Root length grew significantly in the Isfahan ecotype under M4 and M17 treatments, whereas the shortest roots were observed in the Karaj ecotype under the M20 treatment. The highest number of leaves was observed in the Shiraz ecotype by the M4 treatment, whereas the lowest number of leaves was recorded in the Karaj ecotype as a result of the M8 treatment.