Generation of adventitious roots and characteristics of gas exchange according to leaf number of hemp (Cannabis sativa L.) cuttings

Abstract

In the hemp-seedling industry, the number of leaves on the harvested cuttings from mother plants is crucial for survival. Therefore, the present study determined the suitable number of leaves on hemp (Cannabis sativa L.) cuttings to promote adventitious root (AR) formation. Hemp cuttings with two, three, and four leaves were harvested from the apex of the mother plant. After disinfecting their base, 18 cuttings per replication were transplanted into a plug tray (72 holes) filled with a horticultural substrate. The photosynthetic characteristics of the cuttings and well-rooted hemp plants were measured at 22 and 60 days after transplantation (DAT), respectively. At 22 DAT, the average AR length, AR fresh weight, AR generation rate, and average number of ARs were the highest from two-leaf cuttings. Due to the higher AR generation, the net photosynthetic rate was the highest in cuttings with two-leaf cuttings at all the light intensity conditions (0, 50, 100, 175, 250, 500, 750, 1,000, and 1,500 μmol·m-2·s-1). The initial AR development of cuttings with two leaves likely enabled sufficient water uptake and photosynthesis to increase the survival rate. Growers may increase the productivity per unit area of well-rooted hemp plants by harvesting cuttings with two leaves.