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GRAFTING AND BUDDING
Grafting - the joining of separate plant parts together, such that they form a union and grow as one
               plant
 .
scion or cion - the upper part of the graft that becomes the shoot system of the
                       new plant.

stock, rootstock or understock - the lower part of the graft that becomes the
                                                  root system of the new plant.

 
Budding - a type of grafting where the scion is just a bud piece or small chip of wood with a bud
                 attached.
 

REASONS FOR GRAFTING OR BUDDING
1) Plants cannot be propagated by other means, ex. plants in adult phase
2) Decrease time to flowering and fruiting, especially fruit and nut trees
3) Obtain desirable characteristics of rootstock, such as:
    a) disease resistance
    b) adapted to soils or climate in various regions
    c) dwarfing
4) Change variety, topwork mature trees 
5) Special forms, usually for ornamental purposes, ex. tree roses
6) Repair damage (inarching, brace graft, bridge graft)
7) Virus indexing, used for diagnosing virus diseases 
 

STAGES OF GRAFT AND BUD UNION FORMATION
Prerequisite- must match cambium of stock with cambium of scion
1) Callus formation by both stock and scion
2) Intermingling of callus from stock and scion
3) New cambium forms in callus between stock and scion
4) New secondary xylem and phloem from new cambium to  connect stock and scion
 

FACTORS AFFECTING SUCCESS OF GRAFTING OR BUDDING
1) Plant type - can only graft dicots and gymnosperms; not monocots (lack a cambium)
2) Plant Relationship - within species is most successful
3) Incompatibility - sometimes graft or bud is rejected, even if within species
4) Season and growth state - best when cambium is active, but without leaf growth
5) Environment - must supply proper temperature, humidity, etc.