How a cactus closes a wound

Controlled damage

The researchers made annular cuts in the outer tissues of stem segments, including the epidermis, hypodermis and part of the cortical parenchyma. Vascular bundles and pith remained continuous. Plants were maintained in a chamber at 30°C by day and 20°C at night, with healing observed through day 31. This setup allowed a wound with a known course to be compared with the behaviour of the entire segment. [Mylo et al. 2020]

First, edge change and sealing

Wound edges gradually curled inwards, reducing the exposed surface. A pale layer of dead cells appeared during the first week. Within the first few days, staining already showed deposition of lipophilic substances in the boundary zone, interpreted as an early barrier associated with suberisation. [Mylo et al. 2020]

Wall lignification increased later. Signs of this process were found earlier in prickly pear than in cholla. Formation of a chemical barrier and dead surface layer limits contact between living tissues and the surroundings, while new protective tissue begins to organise deeper inside. [Mylo et al. 2020]

Wound periderm

By the end of observation, both species had formed wound periderm, including tissues produced by a new cork-forming meristem. In O. ficus-indica, an increase in parenchyma cells at the wound zone was more pronounced. In some places, connections between new layers remained mechanically delicate. [Mylo et al. 2020]

Restoring the barrier and stem load-bearing capacity

Repeated bending tests revealed different patterns of mechanical change. In C. bigelovii, some stiffness measures increased after initial weakening. However, individual parameters responded differently, and recovery of properties was less pronounced in O. ficus-indica. Mechanical assessment therefore requires identifying the measured trait, whether stiffness, deformation work or resistance to further damage. [Mylo et al. 2020]

Viewing a dry wound surface provides information on its external state. Microscopy identifies development of new layers, and mechanical measurement describes load-bearing capacity. These three scales complement one another, showing regeneration as a process occurring simultaneously in structure, wall chemistry and organ function. [Mylo et al. 2020]

Connection with vegetative reproduction

An easily detached cholla segment can begin independent growth if it retains water and living tissues, then forms roots. The controlled-cut study explains part of this pathway, barrier formation and tissue remodelling. Complete detachment of a propagule creates a different physiological burden, because it also interrupts the vascular connection with the stock plant. [Mylo et al. 2020][Mylo et al. 2022][Bobich 2005]