2019 ASHS Annual Conference

Previous research has shown that submist propagation systems, which apply water only to the basal ends of cuttings inserted into a closed chamber, may produce measures of rooting for Syringa pubescens subsp. patula ‘Miss Kim’ (manchurian lilac) that are superior to those of overhead mist. We collected cuttings of manchurian lilac in July, 2018 to evaluate photosynthesis in each system along with a combination system (overhead mist plus submist). Cuttings grown in submist retained the greatest number of leaves. Compared to the overhead mist, the number of roots per cutting was more than five times greater in the combination system and more than three times greater in submist. Root dry weight and root length were greatest among cuttings rooted in the combination system. All traits considered were lowest when cuttings were rooted in traditional mist. Leaf-level net photosynthesis was compared among the three systems using a Li-Cor 6400 portable photosynthesis meter. Photosynthesis was low early in the rooting period (0.8 to 1.2 µmol CO²·m²·s^-1) and increased over time to a high of 16.3 µmol CO²·m²·s^-1, but did not differ among systems on most measurement dates. The difference in cutting performance among these systems is not due to differences in photosynthesis, so the physiological basis for rooting responses still remains to be determined. Future work will focus on exploring both the feasibility and commercial scalability of submist propagation systems.