We know that " in grafting, as well as budding, the vascular cambium of the scion or bud must be aligned with the vascular cambium of rootstock. In woody plants the cambium is a very thin ribbon of actively dividing cells located just below the bark. The cambium produces conductive tissue for the actively growing plant (Figure 1). This vascular cambium initiates callus tissue at the graft and bud unions in addition to stimulating tissue growth on the basal ends of many vegetative cuttings before they have rooted." Grafting and Budding Nursery Crop Plants | NC State Extension Publications . That’s why as I mentioned I think transportation is a better subject to be broken out into a different thread and not part of cambium though I see the relationship. As one study says " The xylem in fruit of a number of species becomes dysfunctional as the fruit develops, resulting in a reduction of xylem inflow to the fruit. Such a reduction may have consequential effects on the mineral balance of the fruit. The aim of this study was to elucidate the dynamics and nature of xylem failure in developing apples (Malus domestica ) showing differing susceptibilities to bitter pit, a calcium‐related disorder." That’s clearly not a discussion on grafting or cambium Causes and Effects of Changes in Xylem Functionality in Apple Fruit . I’ve implied the need for discussion many times with threads like this Pear Rootstock influence on pears fruit size, tree growth, nutrition, longevity etc and this Pear rootstocks influence on Fruit size. It’s my belief as an example ohxf333 has smaller fruit for years after planting it that are inferior to other fruit. That’s just it its a belief. Have seen no studies to support that as its based on observation and has nothing to do with cambium contact, color, or callusing. For those wanting to know more on the hypothesis and observations on this subject that’s not about cambium see this sap | plant physiology | Britannica
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