Several fruit crops suffer greatly from unfruitfulness, which costs growers a great deal of money and reduces the profitability of fruit production. When a plant in a fruit crop is in an unfruitful state, it cannot blossom or produce fruit. Yet, unfruitfulness has both internal and external causes, which can be broadly divided into two types. Dichogamy is one of the intrinsic reasons that inhibits perfect and monoecious flowers from self-pollinating. Heterostyly, or flowers with varying style length, is a typical occurrence in Prunus fruits. The proportion of aborted pollen grains varied from 22.5 to 48.0% in cashewnut. In apricot cv. ‘Trevatt Blue’, multiple ovules and anthers with degenerated microspores resulted in both female and male sterility and in ‘Tokaloglu’, the reason for unfruitfulness is self-incompatibility (Gulcan and Askin, 1991). External factors, like temperature that is above 32 °C, result in desiccation of stigmatic surface and more rapid deterioration of embryo sac occurrence. Diploid, self-fruitful and compatible cultivars of the delectable apple plant ensure cross pollination for maximum yield. The 'Spadona' pear's fruit set and yield improve by roughly 50 to 80% when honeybees are sequentially introduced. The rate of pollen germination and tube growth in pears are increased by foliar application of boron at a dosage of 200 mg-1.