This document discusses various physiological factors that can influence pollen germination and fruitfulness in plants. It describes how the rate of pollen tube growth, timing of pollination, nutritional conditions within the plant, and the age and vigor of plants can all impact pollen viability and the development of flowers and fruits. Slow or delayed pollen tube growth, deficiencies or excesses of nutrients like nitrogen, and changes in a plant's growth status from young to mature can all result in reduced fruit set due to issues with pollination or fertilization.

1. Unfruitfulness
Week – 4
Lecture 2

2. 3- due to physiological influence
Pollen germination and prepotency
(prepotency--- is ability of plants to
transmit its characteristic to its progeny to
a highly uniform degree)
The differences in pollen germination are
attributed to physiological influences,

3. 3- due to physiological influence
Pollen germination and prepotency
Pollen of some plants can not germinate
promptly on its flower but pollen of another
flower geminately quickly (corydalus cava
but c.capnoids, C. jabacea) Inhibition of
Pollen germination of short filament on long
style stigma is inhibited completely or
incompletely,

4. 3- due to physiological influence
• 1. Slow pollen tube growth
Rate of pollen tube growth is a
characterize of variety : time vary 1-2
hours in cacao (bean) 1-2 days in
cucurbits and nearly a year in some oaks
and influenced by environmental
conditioned temperature, vigour nutrient
supply .

5. 3- due to physiological influence
• 1. Slow pollen tube growth
Normal growth is evidence for compatibility and
retarded growth is evidence incompatibility
e.g. (in heterostyled flowers )
in illegitimate pollination 72 hours are required
in legitimate pollination 18 hours.
Clementine mandarin pollen tube growth is very
slow in Clementine but rapid in shamouti pistil

6. 3- due to physiological influence
• 1. Slow pollen tube growth
• Cross and self sterility in apple, pear,
cherries, plumes , citrus and guava is
associated with retarded pollen tube
growth.

7. 3- due to physiological influence
2. Premature and Delayed pollination
• Pollen of date palm are vital for a year or more,
while others undergo progressive deterioration.
• Old pollen growth is slower than fresh
• Premature pollination in pear, peach, plums and
persimmon ,
• Pistil of mango lose their ability to cause pollen
germination and tube growth with 12 hours and
falling off is rapid after 6 hours

8. 3- due to physiological influence
2. Premature and Delayed pollination
• In some cases the delayed pollination
causes the poly-embryonic seeds, while
mono-embryonic can be seen in normal
season

9. 3- due to physiological influence
3. Nutritional conditions within plants
• The inflorescence of vigorous apple, pear,
mango, avocado and coconut tree have
twice as many flowers as those of weak
trees of the same variety
• Same situation holds for number of
functional flowers in banana and grape
cluster
• Nitrogen deficiency is also limiting factors

10. 3- due to physiological influence
• Nutritional conditions within plants
• Sterility is also caused by deficiency which
cause the structural defects such as
flower, pistil, ovule, pollen abortion
• Surplus is also dangerous for flower bud,
flower pistil ovule, stamen anther and
pollen .

11. 3- due to physiological influence
• Nutritional conditions within plants
• N deficiency is limiting factor in all fruit plants for
flowering and fruit setting.
• In alive 0.7-.9 % N no fruit set
• Double give good results
• Experiment results:
• 1.40% N 5.0% fruit setting
• 1.40- 1.60% N 18.3% fruit setting
• Above 1.6% N 30.9 % fruit setting

12. 3- due to physiological influence
• Nutritional conditions within plants
• N deficiency is limiting factor in all fruit plants for
flowering and fruit setting.
• In alive 0.7-.9 % N no fruit set
• Double give good results
• Experiment results:
• 1.40% N 5.0% fruit setting
• 1.40- 1.60% N 18.3% fruit setting
• Above 1.6% N 30.9 % fruit setting

13. 3- due to physiological influence
• 4. Age and vigor of plants
• Age and vigor are influences the fruitfulness but
vigor has more correlating with production of
flowers and their normal development
• A greater abortion of flowers in the cluster of
strawberry, raspberry, walnut and tomato , failure
that occurs early or late in the season
deepening on the growth status

14. 3- due to physiological influence
4. Age and vigor of plants
• The changes from principally pseudo-
hermaphrodite to hermaphroditic in flowers in
many plums varieties as very vigorous young
tree settle down to more normal growth rate
• The appearance of successive cycles of
flowering and fruit setting that alternate with
cycles of fruit and seed development that
temporarily exhaust food reserves.

15. 3- due to physiological influence
• 5. Age and vigor of plants
• Interference of vigor, or its lack, with
fruitfulness and fertility is registered before
rather than after flowering and fertilization .

16. 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