Unfruitfulness and Sterility Associated
with external factors
1- Under stock or grafting
2- Pruning
3- Temperature
4- Soil moisture and atmospheric humidity
5- Light
6- Climatic season and locality
7- Miscellaneous

 Grafting controls size, flowering, fruiting
characteristic, appearance, and nutritive
condition of plants
 These are exerted by the stock not by the
grafting operation it self.
 Due to incompatibility in stock and scion
defective union is the evidence for stuctural
defect in pear/quince

 In roses variety produced by cutting produce
flower freely but few seeds
 Hachiya persimmon on diospyros lotus fail to
fruit set