This study investigated optimal cutting propagation conditions for tomato by simultaneously considering rooting percentage, root system development, shoot growth, and suppression of cut-surface browning. The most effective cutting condition was obtain...
This study investigated optimal cutting propagation conditions for tomato by simultaneously considering rooting percentage, root system development, shoot growth, and suppression of cut-surface browning. The most effective cutting condition was obtained by applying NAA at 1,000 mg L⁻¹ to 15-cm apical
softwood cuttings, in combination with mixed RGB-LED lighting, a horticultural growing medium (HGM), and a nutrient solution electrical conductivity (EC) of 0.5 dS m⁻¹.
In tomato cutting propagation, morphological and physiological growth responses were closely associated with endogenous hormone composition and the
carbon-to-nitrogen (C/N) ratio of the cuttings. Compared with semi-hardwood cuttings, softwood cuttings exhibited higher concentrations of IAA, ABA, JA, and SA, a lower C/N ratio, and greater accumulation of macronutrients such as nitrogen, K, Ca, Mg, and P, indicating a favorable physiological and nutritional basis for root induction and early shoot growth. C/N analysis by stem position further suggested that basal tissues, characterized by higher N content and a lower C/N ratio, may be related to nitrogen metabolism required for rooting. This finding may serve as fundamental physiological evidence to explain differences in rooting capacity depending on the cutting collection position. Moreover, the NAA 1,000 mg L⁻¹ treatment produced the best performance in terms of root number, root diameter, and root fresh weight compared with other auxin treatments and the untreated control, thereby confirming the effectiveness of NAA as a rooting-promoting plant growth regulator (PGR) in tomato cutting propagation.
Hormone analysis revealed position-specific regulatory patterns after NAA treatment: IAA and JA increased in belowground tissues, whereas ABA, JA, and SA increased in aboveground tissues. These results suggest a mechanism in which growth- and defense-related signaling pathways are simultaneously activated in rooting tissues, thereby improving rooting stability.
In addition, NAA treatment reduced the C/N ratio in both aboveground and belowground tissues while enhancing nitrogen accumulation, indicating the formation of an important physiological basis associated with activated nitrogen metabolism and tissue differentiation during the early stage of rooting. Overall, this integrated analysis of hormone compositional changes and C/N regulation provides physiological and biochemical evidence supporting the optimal cutting conditions proposed in this study and can serve as valuable information for establishing strategies for cutting selection, PGR utilization, and nutrient and EC management in commercial tomato cutting seedling production systems