Larch is a cold-temperate tree species native to the northern hemisphere and tolerant to low temperatures. It is one of the most significant timber species in Northeast China. This study examined growth changes in hybrid larch seedlings from five lines to explore the physiological responses of these seedlings to low-temperature stress. Using 8-month-old hybrids of larch seedlings, we subjected the plants to cold stress at 4 °C and freezing stress at −20 °C over three periods of 6, 12, and 24 h, and treatment at 25 °C was used as a control. Results showed that significant correlations were found among the growth indicators, with larch line 1306 having the lowest incremental growth indicators, the largest root-to-crown ratio, and better cold tolerance than the other larch lines. The levels of soluble sugars (SSs), soluble proteins (SPs), malondialdehyde (MDA), and relative electrolyte leakage (REC) increased significantly in all lines under low-temperature stress. The activities of superoxide dismutase (SOD) and catalase (CAT) showed variation over time. Significant correlations were found between MDA and REL, SS, SR, Pro, CAT, and SOD in most of the lines; no significant correlation was found between MDA and the other indices in lines 1301 and 1309; and significant correlations were found between most of the physiological indices in line 1306.

Nandina domestica ‘Firepower’ is one of the most popular colorful foliage species in landscaping. However, it is currently propagated mainly by seeding and cuttings, with a low reproduction coefficient, hindering the cultivation of this species. Therefore, establishing an in vitro regeneration system would be beneficial for the industrialized production of Nandina domestica ‘Firepower’. In this study, an ex vivo regeneration system was established using the direct organogenesis pathway. In early April, the new shoots of Nandina domestica ‘Firepower’ were selected, and the stem segments of 1~2 cm were cut as the disinfection materials for the explants. The optimal formulation for inducing axillary shoots was 1/2 MS + 1.5 mg L⁻¹ 6-benzylaminopurine (BA) + 0.3 mg L⁻¹ indole-3-butric acid (IBA). The optimal formulation for the differentiation and proliferation of axillary shoots was 1/2 MS + 1.5 mg L⁻¹ BA + 0.01 mg L⁻¹ IBA with a multiplicity of proliferation of 9.22. We determined that the rooting of axillary shoots required a combination of IBA, naphthalene acetic acid (NAA), and activated carbon (AC). The optimal formulation for rooting was 1/2 MS + 0.2 mg L⁻¹ NAA + 0.3 mg L⁻¹ IBA + 0.2 mg L⁻¹ AC. After a two-day hardening period for tissue-cultured plantlets, a substrate consisting of peat soil, vermiculite, and perlite at a ratio of 2:2:1 was determined to be the optimal cultivation formulation. This system provides a framework for the industrialized production of Nandina domestica ‘Firepower’.