The document discusses the reproductive processes in higher and lower plants, focusing on post-fertilization changes such as the development of endosperm, embryos, and fruits. It details various types of endosperm, the significance of seeds and fruits, and phenomena like parthenocarpy, apomixis, and polyembryony. Each process is described with examples, highlighting their importance for nourishment, protection, and propagation of plant species.

1. 16
J.
DORA

2. 17
REPRODUCTION IN HIGHER AND LOWER PLANTS
Contents at a Glance :
3.1. Post-Fertilization Changes
3.1.(a). Development of Endosperm
3.1.(b). Types of Endosperm
3.2. Development of Embryo
3.3. Formation & Development of Fruits and Seeds
3.4. Parthenocarpy
3.5. Apomixis
3.6. Polyembryony
3.7. Significance of Fruits and Seeds
3.1. POST-FERTILIZATION CHANGES :
3.1.(a). DEVELOPMENT OF ENDOSPERM :
• Nutritive tissue for the nourishment of developing embryo.
• It is the product of second fertilization or triple fusion is Primary Endosperm Nucleus (PEN).
• It develops into endosperm.
• Endosperm is post fertilization product and is commonly triploid tissue.
• In some case endotherm is totally consumed during embryo development so that the mature seeds
do not process endosperm and sub seeds are called non-endospermic or ex-albuminous seeds. e.g.
pea, bean, gram, groundnut, etc.
• The endosperm versus in the mature seeds and it continues to support the growth of embryo during
steer germination and such seeds are called endospermic or albuminous seeds. e.g. castor,
sunflower, coconut and cereals like maize, wheat, etc.
• Triploid PEN divides mitotically to form nutritive tissue called Endosperm.
• Embryo and endosperm are develop simultaneously.
3.1.(b). TYPES OF ENDOSPERM :
There are 3 types of Endosperm on basis of mode development as follows,
a. Nuclear Type :
• Most common type of Endosperm.
• PEN undergoes free nuclear divisions mitotically without wall formation.
• Not followed by cytokinesis.
• This results, to produce large number of free nuclei freely suspended in common cytoplasm of
Central cell.
• Vacuole appears in the centre of cell, pushing the nuclei towards the periphery.
• Later, cell wall formation occurs around these nucleii in a centripetal manner to form cellular mass.
• Hence, multicellular endosperm is formed.
• But in some cases cell wall formation remains incomplete. e.g. wheat, sunflower and coconut.
• Coconut has multicellular endosperm, free nuclear in the outer part and vacuolated endosperm in
the Centre.

3. 18
b. Cellular Type :
• Less common type of Endosperm.
• Undergoes nuclear divisions followed by cytokinesis.
• Endosperm development occurs in cellular form right from the beginning.
• Mostly seen in dicots.
c.Helobial Type :
• Intermediate type.
• Common in Helobiae series.
• Undergoes nuclear free divisions.
• Divisions of PEN followed by a transverse wall, divides the cell unequally.
• Smaller cell is called chalaza cell larger cell is the micropylar cell.
• Walls develop between nuclei in micropylar chamber.
• Mostly seen in monocots.
e.g. Asphodelus.
3.2. DEVELOPMENT OF EMBRYO :
• The zygote forms of wall around it and is converted into oospore.
• The oospore divides transversely to form a large basal cell towards the micropyle and a small apical
cell towards the interior of embryo sac.
• From this 2-celled stage, until the formation of organs the embryo is commonly called pro-embryo.
• The basal cell divides transversely to form a row of cells called suspensor.
• The suspensors pushes the developing embryo deeper in the endosperm for its proper nutrition.
• The apical cell of the 2-celled pro-embryo undergoes a transverse and two vertical divisions at right
angles to each other to form an octant stage.
• The eight cells of the octant pro-embryo undergo many divisions to form a spherical mass of cells.
• Gradually this mass becomes heart-shaped and then horse-shoe shaped.
• Finally it gets differentiated to form an embryonal access with plumule, radicle and two cotyledons
in dicots and a single cotyledon in monocots.

4. 19
3.3. DEVELOPMENT & FORMATION OF FRUITS AND SEEDS :
SEED FORMATION & DEVELOPMENT :
• Initiated by fertilization.
• Each ovule in the ovary also enlarges in size.
• Seed consists of two distinct coverings,
outer seed coat- the testa and the
inner coat- membranous tegmen.
• In seeds, embryo reserves food in endosperm.
• Endosperm remains conspicuous.
• Cotyledons in endospermic seeds is first
photosynthetic organ.
• The resultant seed is endospermic or albuminous.
e.g. Castor, Coconut, Maize, etc.
• In other seeds, embryo absorbs food reserve
from the endosperm.
• Endosperm disorganizes.
• Cotyledons in non-endospermic seeds act as a food storage.
• The resultant seed is non-endospermic or ex-albuminous
e.g. Pea, bean, etc.
Micropyle - a small pore in seed coat to allow the entry of water and oxygen during soaking.
FRUIT FORMATION & DEVELOPMENT :
• Fruit development is triggered by hormones.
• With the development of embryo and endosperm,
ovary enlarges in size.
• Sepals, petals, stamens, style and stigma fall off and
ovary changes into fruit.
• Ovary wall changes into pericarp (fruit wall) which may
differentiated into epicarp, mesocarp and endocarp.
• Pericarp is initially green in colour and on ripening becomes
• orange, red, purple, yellow, etc.
• e.g. mango, coconut, etc.
OR
• Fruit development is triggered by hormones.
• After fertilization, zygote is formed and the
ovary begins to differentiate into the fruit.
• Ovary wall develops into pericarp.
• Pericarp is three layered which get
differentiated in the fleshy fruit.
• e.g. mango, coconut, etc.

5. 20
SIGNIFICANCE OF SEEDS & FRUITS :
• Fruits provide nourishment to the developing seeds.
• Fruits protect the seeds in immature condition.
• Seeds serve as important propagating organs (units) of plant.
• Seeds and fruits develop special devices for their dispersal.
• Help in the distribution of the species.
1) Dormancy :
• Temporary suspension of growth.
• A state of metabolic arrest that facilitates the survival of organisms during adverse environmental
conditions.
• Structural or physiological adaptive mechanism for survival is called dormancy.
• During this period, seeds are dispersed at different places.
2) Viability :
• Ability of seeds to germinate after dormancy period.
• Viable seeds not germinate in favorable condition.
3) Reserve Food :
Fully developed embryo is nourished by food stored in either endosperm or cotyledons during
germination of seed and a seedling is produced.
4) Protective Coat :
Testa, the outer, hard seed coat, gives protection against the mechanical shocks, fluctuations in
temperature and dry conditions. Animals eat fruits and either through away seeds or if our consumed,
they are not digested due to the hard seed coat and removed through excreta.
5) Dispersal :
Some seeds produce various structures like wings, pappus calyx (persistent and hairy), hooks or sticky
substance and seeds are actively or passively transported to distant places.
6) Edible Fruits :
Many fruits are consumed by different organisms and seeds are thrown does. Thus, development of
fruits and seeds place significant role in the spread of the species.

6. 21
3.4. PARTHENOCARPY
• Term is coined by Noll.
• The condition in which fruit is developed without fertilization called Parthenocarpy.
• Such fruits like Pineapple, Banana, Papaya, called Parthenocarpic fruits.
• Parthenocarpic fruits are seedless and hence are preferred by consumers.
• Parthenocarpy can be induced through application of growth hormones like gibberellins, e.g.
seedless grapes.
• The placental tissue in the unfertilized ovary produces auxin IAA (Indole-3 Acetic Acid)
• Responsible for enlargement of ovary into fruit.
1. Parthenogenesis is the development of embryo directly from egg cell or a male gamete.
It is a kind of apogamy.
2. Agamospermy : Plants produce seeds. Embryo produced without meiosis and Syngamy.
3. Parthenocarpy can be induced artificially by - spraying of gibberellins, delaying pollination, use
of foreign pollens, etc.
4. Genetically uniform parental type seedlings are obtained from nuclear embryo.
3.5. APOMIXIS :
• Phenomenon of formation of embryo through asexual reproduction.
• Without formation of gametes.
• Unusual sexual reproduction where there is no meiosis and syngamy.
• Embryo develops → ovule develops →seed .
• When a gametophyte cell produces embryo like structure without fertilization, it is called as
apogamy.
• When diploid sporophyte cell produces a diploid gametophyte without undergoing meiosis is called
apospory.
e.g. Orange, Mango.
OR
• Some species of family Asteraceae and some grasses seeds are produced without fertilization.
• This is called called Apomixis and such seeds are called apomictic seeds.
• Apomixis is a form of asexual reproduction that mimics sexual reproduction.
• Diploid egg cell is formed without meiosis and it develops into an embryo without fertilization.
• Thus, apomictic seeds can be formed.
• When a gametophyte cell produces embryo like structure without fertilization, it is called as
apogamy.
• When diploid sporophyte cell produces a diploid gametophyte without undergoing meiosis is called
apospory.
e.g. Orange, Mango.
TYPES OF APOMIXIS :
a. Recurrent apomixis :
❖Embryo sac generally rise from an archesporial cell.
❖In diplospory, the unreduced embryo sac is derived from the diploid megaspore mother cell.
e.g. Taraxacum.
❖In apospory, the nuclear cells give rise to embryo sac.

7. 22
b. Non-recurrent apomixis :
❖Megaspore mother cell undergoes meiotic division and a haploid embryo sac is formed.
❖Embryo arises from the egg by parthenogenesis.
❖Plants produced by this method are generally sterile and do not reproduce sexually.
e.g. Nicotiana.
c. Adventive Embryony :
❖Embryos develop from somatic nucleus or integuments along with normal zygotic embryo.
❖It is common in Mango, Orange, Lemon, etc.
❖It gives rise to a condition called polyembryony.
3.6. POLYEMBRYONY :
• Development of more than one embryo inside the seed is called as polyembryony
• First discovered by Leeuwenhoek in the seeds of Citrus genus.
• Resulting multiple seedlings.
• Polyembryony may be true or false depending upon whether many embryos arise in the same
embryo sac or in different embryo sacs in the same ovule.
• In adventive polyembryony, an embryo develop directly from the diploid cell of nucleus and
integuments as in Citrus.
• In cleavage polyembryony, zygote pre-embryo sometimes divides (cleaves) into many parts or units.
• Each unit then develops into an embryo.
SIGNIFICANCE OF POLYEMBRYONY :
• Polyembryony increases the chances of survival of the new plants.
• Nuclear adventive polyembryony is of great significance in horticulture.