Physiological Study of Graft Union Formation in Cactus

Abstract

Young seedlings of Notocactus submammulosus var. pampeanus cut transversely were placed onto transverse cut surfaces of young plants of Hylocereus trigonus. Vascular connection between stock and scion occurred in almost all grafts 20 days after grafting when cut ends of vascular bundles of stock and scion were placed together (Method I). When they were 1 or 3mm apart transversely to each other (Method II or III), vascular connection occurred in only 40 or 10% of grafts.By the Method II, NAA, IAA and 2, 4-D promoted vascular connnection, and also increased the diameter of the vascular bundle connecting those of stock and scion. NAA (100ppm) was most effective when applied three times every three days after grafting.TIBA (0.1% in lanolin), a well-known inhibitor of basipetal transport of auxin, inhibited vascular connection strongly. But, by subsequent NAA (0.01% in lanolin) applications, this inhibitory effect of TIBA was effaced completely.When lanolin with NAA (0.01%) was applied instead of a scion, it also induced a cambium in the area of the tissue between the lanolin and the vascular cut end of the stock.The results suggested that the vascular connection in cactus grafts may be controlled by endogenous auxin of scions.