Rooting of sugi cuttings in closed and semi-closed conditions under mist irrigation

ABSTRACT We examined whether 100% atmospheric humidity had a positive or negative effect on rooting rate and root development in sugi shoot cuttings. To assess the effectiveness of producing shoot cuttings using the “aerial cutting” method, we compared the rooting rate, root mass and shoot growth of sugi shoot cuttings reared in a closed environment with nearly 100% atmospheric humidity (vapor pressure deficit (VPD) = 0; closed aerial cuttings (CL)) with individuals grown in an open environment (VPD>0; open aerial cuttings (OP) and open aquaculture cuttings (AQ)). The results showed that an atmospheric humidity of 100% had a negative effect on rooting. The CL shoot cuttings tended to have a lower rooting rate and smaller root dry mass compared to cuttings grown under open conditions (OP and AQ), suggesting a possibility that the rooting of sugi cuttings requires moderate water stress so that the water-absorbing organs can develop and compensate for water loss due to transpiration. Shoot elongation was highest in CL shoot cuttings with frequent mist irrigation, and the lowest in AQ shoot cuttings with no foliar water uptake (FWU) above the water level. The findings suggest that FWU promoted stem elongation in CL shoot cuttings without roots.