This document discusses the morphology and reproductive systems of major crops. It covers topics such as growth and development stages, floral biology, pollination, reproduction, and mechanisms that encourage cross-pollination over self-pollination. These include floral structures like dichogamy and heterostyly that separate male and female parts in time or space, as well as self-incompatibility genes and male sterility traits. The document seeks to explain genetic and physiological reasons for allogamy being favored in many crop species.

1. Morphology & Reproductive
System of Major Crops
By:
Muhammad Anas Rasool
AGL-15-07

2. Overview
• Growth & Development
• Floral Biology & Pollination
• Reproduction
• Floral Mechanisms
• Reasons for Allogamy
• Genetic Factors influencing Pollination Behavior
• Floral Morphology Supporting Cross Pollination
• Self Incompatibility Mechanism
• Male Sterility
• Decliny

3. Growth & Development
• Growth
• Development
• Stages of Plant Growth
1. Germination
2. Vegetative Stage
3. Reproductive Stage
4. Ripening Stage
5. Senescence

4. Growth & Development
• Quantitative and irreversible change/increase in number,
volume (size) or weight of cell, tissue or organ in plant
life cycle.
• Development is qualitative change in function, no. of
cells, tissues, organs or the entire plant.
• Stages of Plant Growth
i. Germination
ii. Vegetative Stage
iii. Reproductive Stage
iv. Ripening Stage
v. Senescence

5. Floral Biology & Pollination
• Floral Structure
• Pollination
i. Cross Pollination
ii. Self Pollination
• Fertilization
• Double Fertilization

6. Floral Biology & Pollination

7. Floral Biology & Pollination
Pollination:
•Pollination is the act of transferring pollen grains from
the male anther of a flower to the female stigma.
•Self-pollination is when pollen from anther of flower
arrives at the stigma of a the same flower.

8. Floral Biology & Pollination
• Cross-pollination is the transfer of pollen from the
male reproductive organ of one plant to the female
reproductive organ of another plant.
• Insects and wind are the main agents of cross-
pollination.

9. Floral Biology & Pollination
Fertilization :
Fertilization is the union of male and female gametes
(reproductive cells) to produce a zygote (fertilized egg).
•Step 1: Pollination
•Step 2: Germination
•Step 3: Penetration in the Ovule
•Step 4: Fertilization

10. Floral Biology & Pollination
Double
Fertilization:
Fertilization process in
which one sperm cell of a
pollen grain fertilizes an egg
cell while a second fuses
with two polar nuclei to
produce a triploid body that
gives rise to the endosperm.

11. Reproduction
• Reproduction
a. Sexual reproduction
b. Asexual reproduction
c. Vegetative reproduction

12. Reproduction
• Reproduction is the process by which an organism
produces others of its same kind.

13. Reproduction
Asexual Reproduction:
•Asexual reproduction is a type of reproduction by
which offspring arise from a single organism, and
inherit the genes of that parent only; it does not involve
the fusion of gametes, and almost never changes the
number of chromosomes.

14. Reproduction
Sexual Reproduction:
•Sexual Reproduction requires two parents.
•The female parent provides an egg cell, and the male
parent provides a sperm cell. The egg cell and the sperm
cell combine to form a new individual.
Egg cell Sperm cell New individual

15. Reproduction
Vegetative Propagation:
•Vegetative propagation occurs when a new plant grows
off an existing part of an old plant.
•Many plants can use vegetative propagation. Like:
Grasses – Potato plants – Strawberries.

16. Floral Mechanisms
1. Cleistogamy (Viola, Oxalis)
2. Chasmogamy
i. Autogamy (Wheat, Rice)
ii. Allogamy (Sunflower, Maize)

17. Reasons for Allogamy
• Self incompatibility
• Dichogamy
• Cytogenetic reasons

18. Genetic Factors influencing
Pollination Behavior
• Polyploidy
– Autopolyploidy
– Allopolyploidy
• Aneuploidy
– Nullisomic
– Monosomic
– Trisomic
– Tetrasomic

19. Floral Morphology Supporting
Cross Pollination
• Dioecious Plants
• Monoecious plants
• Self pollination prevented by floral structure
1. Dichogamy
2. Heterostyly

20. Floral Morphology Supporting
Cross Pollination
• Dioecious Plants (Date palm, Papaya)
• Monoecious plants (Maize)
• Dichogamy:
The ripening time of pistil and anthers in a
flower do not coincide. It is of two types:
1. Protandry (Pearl Millet)
2. Protogyny (Plantago)

21. Floral Morphology Supporting
Cross Pollination
Heterostyly:
Stamens & pistils are of different lengths.
a.Pin Flowers
b.Thrum Flowers
c.Natal Plum

22. Incompatibility Mechanism
• Physiological reasons
– Pollen on stigma fails to germinate
– Pollen may germinate but tube growth is slow.
• Genetic Reasons
– Gene ‘S’ in Nicotiana shows multiple
allelomorphism.

23. Incompatibility Mechanism

24. Male Sterility
• Male sterility
– Genetic Male sterility
– Cytoplasmic Male Sterility
– Cytoplasmic-Genetic Male Sterility

25. Male Sterility
• Male sterility is defined as an absence or non-
function of pollen grain in plant or incapability of
plants to produce or release functional pollen grains.

26. Male Sterility
Genetic Male sterility:
•The pollen sterility, which is caused by nuclear genes,
is termed as genic or genetic male sterility.
•It is usually governed by a single recessive gene “ms”
or ‘s’, but dominant gene governing male sterility are
also known.

27. Male Sterility
Cytoplasmic Male sterility:
•The pollen sterility which is controlled by cytoplasmic
genes is known as cytoplasmic male sterility (CMS).
•Usually the cytoplasm of zygote comes primarily from
the eggs cell and due to this progeny of such male
sterile plants would always be male sterile.

28. Male Sterility

29. Dicliny
• It refers to unisexual flowers or a condition in
flowering plants in which flowers become staminate
or pistillate.
• Examples: Papaya, Date palm

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