Genetic Factors for Unfruitfulness
A land is said to be self sterile if it does not fruit with its pollen. Often many varieties of fruits are partially self sterile giving a poor fruit set with their own pollen.
Some varieties do not set fruit only with their own pollens but also with the pollens of several other varieties. They are said to be besides being self sterile, cross sterile in respect of those varieties. They will set the fruits with the pollens of certain other varieties which supply them compatible pollens. Such varieties can fruit only when compatible pollens are available in the vicinity.
2) Hybrid Condition:
Hybrid between distantly related from are sometimes to produced self sterility.
In several deciduous fruits, the pollen of some varieties are in capable of fertilizing the flowers of certain other varieties or of the some variety.
1) Slow Growth of Pollen Tube:
Poor growth rate of pollen tube in the style, possible due to hormonal control. The growth rate of pollen tube may be slow due to several causes including low temperature.
2) Nutritive Condition within the Plant:
Nutritive conditions of a plant just before or at or just after the time of blossoming is important in determining the percentage of flowers carrying for setting and for maturity. Its effect may be on pollen viability or on fertility of pistils. So far the internal conditions of plant are concerned deficiencies of carbohydrate results in failure of crop.
On the basis of nutritional status, fruit trees have been divided into 4 general grops.
Plants in this group make poor growth and bear little crop or no fruit shaded or over crowded trees falls in this category.
Excess of nitrogen is present with sufficient amount of carbohydrates for strong and succulent growth.
Excess of carbohydrates leads the plants to its favorable growth and fruit set. Under such condition optimum fruitfulness can be obtained.
Excess amount of carbohydrates and small quantity of nitrogen leads to the poor growth of and small amount f fruits, Neglected trees fall under such category.