Preliminary Study on the Critical Vernalization Temperature and Physiological Responses of Sedum plumbizincicola

Most Sedum plumbizincicola shoots will die after flowering, greatly affecting its growth and cadmium (Cd) uptake from polluted soils. Here, a pot experiment was conducted to investigate the vernalization conditions and physiological responses of Sedum to different temperature treatments of varying duration. The study established the following four experimental treatments: a) the Sedum robust seedlings were placed in a 4, 8, or 12 ℃ constant temperature and light growth chamber for 14, 21, 28, 35, 42, 49, or 56 days of low-temperature pre-treatment before being transferred to a 23 ℃ growth chamber for continued cultivation; b) the seedlings received 123 days of continuous 23 ℃ treatment in the incubator before transitioning to ambient conditions; c) the seedlings underwent 123 days of continuous 4 ℃ low-temperature pre-treatment followed by ambient adaptation; d) the seedlings of the control group maintained in outdoor ambient conditions. Eight healthy and robust Sedum seedlings were selected for each treatment. The experiment started on December 22, 2023 and was harvested on July 2, 2024. The results of the study show: The 4 ℃ low-temperature treatment promoted flowering, and the flowering date and rate gradually increased with increasing time in the low-temperature treatment, and the critical temperature of vernalization was 4-8 ℃; In the 4 ℃ treatment the vernalization time was 35 days, and 49 days were required for complete vernalization; From 14 to 56 days the 4 ℃ low-temperature treatment significantly increased plant stem diameter and height but had no significant effect on shoot biomass; After 49 days of the low-temperature treatment at 4 ℃ the stem diameter and plant height at harvest appeared to be higher than those in the consistent 23 ℃ treatment, but no significant difference was observed in shoot biomass between the two treatments; Compared to the consistent 23 ℃ treatment the chlorophyll and total nitrogen contents of leaves decreased significantly after 56 days in the 4 ℃ treatment during the full flowering period; In contrast, the foliar contents of soluble sugars, starch, soluble proteins, and the carbon-to-nitrogen ratio (C/N) were higher in the 4 ℃ treatment than the consistent 23 ℃ treatment. Therefore, increasing the ambient temperature during the growth period of Sedum can effectively inhibit the vernalization process. This provides a valuable basis for the regulation of the flowering period of S. plumbizincicola, the realization of less or no flowering, and the continuous growth and cutting, to increase the Cd phytoextraction efficiency of the hyperaccumulator in polluted soils.