inflorescence, pollination and fertilization
TRANSCRIPT
INFLORESCENCE, POLLINATION AND FERTILIZATION
Prepared to meet the task Structur and Development of Plants 1
ARTICLE
By
Niswati Zahro
NIM 100210103068
PROGRAM STUDY EDUCATION SCIENCE OF BIOLOGY
FACULTY OF TEACHER TRAINING AND EDUCATION
UNIVERSITAS JEMBER
2011
INFLORESCENCE, POLLINATION AND FERTILIZATION
Niswati Zahro
(100210103068)
ABSTRACT
Before plants was die, usually it will produce a component that will become new
plant called flower. Inflorescence is the arrangement of a group of flowers borne
on the same main stalk. In a racemose (or indefinite) inflorescence the tip of the
main stem continues to grow and flowers arise below it. Flower have many part to
support fertilization and pollination even to form fruit that have seeds.
Pollination is the process by which pollen is transferred in plants, thereby
enabling fertilization and sexual reproduction. Pollen grains, which contain the
male gametes (sperm) to where the female gamete(s) are contained within
the carpel. Fertilization is fused even of ovum and sperm after pollination.
Key word: inflorescence, pollination, fertilization, fused
1. Introduction
Plant reproductive organs differentiated into 2 groups, namely generative
reproduction and vegetative reproduction. Generative organs has a shape and
arrangement of which varies according to species of plants, but spermatophyta,
commonly referred to as a flowers. Therefore, a plant seed, if it is time to
reproduce flowers. There are two types of flowering is a single flowering (planta
uniflora) and compound flowering (inflorescentia). In a planta uniflora, only
supports a single flower stalk, while the inflorescentia, a flower stalk to support
many flowers. Inflorescence should be distinguished from the branch that
supports some of flowers in axillary, but not easy to distinguish a compound
interest from the branch that has the flowers in axillary leaves (Tjitrosoepomo,
2009).
Flowers is the plant’s organ which will become fruit and in fruit, seed will be
happening in there potential make a new plant that is cotyledons. Fruits, seeds and
cotyledons will occur after the first event pollination and fertilization
(Tjitrosoepomo, 2009). Reproductive parts are located within the flowers. Plants
may be unisexual or bisexual, i.e the male and female reproductive parts located
within the same flower or on separate flowers. The male reproductive organ is
known as Androecium while the female is known as Gynoecium. The
Androecium is composed of stamens that is made of up a filament and anther. The
anther contains pollen sac that produces pollens. Male gametes are contained
within the pollens. Both gymnsosperms and angiosperms belong to the
spermatophyta or flowering plants family, the difference being mainly how the
seed are borne. However, the pollination and fertilization mechanisms, though
similar in actual context also have differences (Sengupta, 2010). Based on the
above background, it is necessary to do a study to add insight the students to
better understand inflorescence, pollination and fertilization events.
2. Inflorescence
Flowers may be born singly on plants, when they are said to be solitary, or they
may from clusters. Such clusters of flowers, together with the stems and bracts
associated with them, are called inflorescences. Some flowers heads are extremely
complex, expecially in the grasses and in the family to which the dandelion and
daisy belong, each head consisting of many dozen or even hundreds of individual
flowers (Sengupta, 2010)..Compound.flower has the parts.that are like the
stem, like.a.leaf, as.well.as parts.if atypical flower, like.a crown of.flowers, pistil,
and benangsari.The parts that are like stem, for example:
a) Main flower stalk (peduncle, pedunculus), which is the main which supports.
whole compound flowers.
b) Section mother flower stalk inthe middle.of the.inflorescence,in which.the indi
vidual flower stems attac.ed, called.the rachis (rachis)..Flower stalk (pedicel, p
edicellus), the stalk of.each individual flower
c) Basic flower (receptacle, receptaculum), base of flowers stalks that support
other parts of flower. (Sengupta, 2010).
The parts are like a leaf, for example (Dillon, 1964):
a) Protective leaf (bractea), leaf likes the main axillary leaf
b) Leaf stalks (bracteole), that is leaves (1-2 leaves) that appear on base
flower stalks.
c) Flower sheath (spatha), leaves are larges shield that surrounds the whole
compound flowers prior to bloom, for example on flower Palm palmae.
d) Leaf pads (involucrum), an amount of protective leaves arranged in a
circle around the compound flowers basis, for example in the Hellianthus
annus L.
e) Leaf additional (epicalyx), an around of protecetive leaves arranged the
petals for example in Hibiscus rosa-sinensis.
f) Sepal
g) Petal
h) Tepal
i) Stamen
j) Pistil
Generalized parts of flower
3. Type of Inflorescences
Based on bud growth, the introduction of monopodial growth and simpodial. Two
kinds of growth were also reflected in the growth of flower:
1. Compound flower is limited growth (inflorescentia cymosa) that is compound
flower who stalks is always covered by a flower, so the main stalks has
limited growth. Flowers that bloom first is contained in the main flower stalks,
so from the middle to the edge. Base of branches in the main stalk, compound
flower bounded distinguished into three kinds ( Tjitrosoepomo, 2009):
a) Monochasial, if the main stalks has only one branch stems, there are
two branches but never confronted and which one is larger than the
other branches
b) Dichasial, if at the main stalk rise out of two branches dealing
c) Pleiochasial, if the main stalk rise out more than two branches at the
same height somewhere on the main stalk.
2. Compound flower is unlimited growth (inflorescentia racemosa), compound
flower that main stalks can continue grow branched which can be branched
again and have acropetal arrangement (the younger flower closer premises
main stalk and flower bloom from bottom to top.
Pleiochasial cyme
Kinds compound.interest limitless with nobranching on main stalk (Sengupta,
2010) :
Spike
A Spike is a group of flowers arising
from the main stem, without
individual flower stalks (sessile).
The example is Agastache
foeniculum.
Raceme
A Raceme is a flower spike where the
flowers have stalks of equal length,
and the tip of the stem continues to
grow and produce more flowers.
Flowers open from the bottom up.
The example is Linaria vulgaris.
Panicle
A Panicle is a branched raceme, each
branch having a smaller raceme of
flowers. The terminal bud of each
branch continues to grow, producing
more side shoots and more flowers.
The example is Lagerstroemia indica.
Cyme
A Cyme is a group of flowers in
which the end of each growing point
produces a flower, so new growth
comes from side shoots and the oldest
flowers are at the top.
The example is Geranium pratense.
Verticillaster
A Verticillaster is a whorled
inflorescence, where the flowers are
borne in rings at intervals up the stem.
The tip continues to grow, producing
more whorls. This type of
inflorescence is common in members
of the Deadnettle/Mint Family
(Lamiaceae).
The example is Phlomis russelliana.
Corymb
A Corymb is a flower cluster where
all the flowers are at the same level,
with flower stalks of different lengths,
forming a flat-topped flower cluster.
The example is Achillea millefolium.
Umbel
An Umbel is a flower head in which
all the flower stalks are of the same
length, so that the flower head is
rounded like an umbrella. Many bulbs
have this type of flower head.
The example is Nerine bowdenii.
Compound Umbel
A Compound Umbel is an umbel
where each stalk of the umbel
produces a smaller umbel of flowers.
This type of inflorescence is typical of
members of the Celery Family
(Apiaceae).
The example is Crithmum maritimum.
Capitulum
A Capitulum is a flower head
composed of many separate unstalked
flowers close together. This type of
inflorescence is typical of the Daisy
Family (Asteraceae), where the outer
flowers have one conspicuous large
petal and the central disk is formed of
flowers with smaller petals.
The example is a Senecio species.
Like everything else in nature, these descriptions can only be a general guide to
how your flowers might look. There are many variables, even on one plant, and
flower clusters are often described as raceme-like cymes, or cymose panicles, or
other words that indicate that the flowers do not conform exactly to any one type
of inflorescence. The habit of growth may also be affected by growing conditions,
so something that produces clear whorls in moist conditions might produce
flowers closer together to form a denser spike in drier conditions. I generally refer
to anything in long, thin inflorescences as a spike, and anything more rounded as a
cluster (Curtis, 1968).
3. Mixture of compound flower (inflorescentia mixta), that is compound
flower who shows good properties as well as the nature of compound
flower limited and compound flower limitless (Marsland, 1964).
4. Reproduction in the flower
Pollination and fertilization are the two processes that aid in plant reproduction.
These two processes are indeed different from each other, but are interconnected
with each other. Pollination is the first step preceded by fertilization that finally
leads to formation of plant zygote. A successful pollination leads to fertilization.
Significant differences are observed on comparing pollination vs fertilization. But
before doing the in depth analysis of the difference between pollination and
fertilization in plants, we must know the basic structure of plant reproductive
system (Marsland, 1964).
4.1 Gynoecium
The gynoecium consists of the stigma, style, and ovary containing one or
more ovules. Stigma- the stigma is female part of the flower. This is where the
seeds are made. The stigma is sticky to catch the grains of pollen. The style is the
neck that the pollen travels down to get to the Ovary. I n the ovary, the pollen
joins the ovule and the ovules become seeds. The Receptacle is the top of the
flower. These three structures are often termed a pistil or carpel. In many plants,
the pistils will fuse for all or part of their length (Marsland, 1964).
The female reproductive part or Gynoecium is composed of one or more pistils.
Pistil contains carpels and carpels house ovary and ovules. Female gametes are
located inside ovules. Pistil has three parts namely stigma, style and filament. The
stigma forms the receptor of pollen grains that is supported by stalk. The pollen
grains pass through the style, filament and finally reaches the ovule. The ovary
contains one or more ovules, which in turn contain one female gametophyte, also
referred to in angiosperms as the embryo sac. Some plants, such as cherry, have
only a single ovary which produces two ovules. Only one ovule will develop into
a seed (Marsland, 1964). .
4.2 Stamen
Stamen are the male parts of the flower. They make the pollen. Pollen is the fine
yellow powder needed to make a new plant. Each stamen has two parts, the
anther and the filament. The anther contains the pollen and the filament holds up
the anther (Stein, 2010).
a. Filament
b. Anther, discharging pollen
5. Pollination
When the pollen is fully developed, the pollen sac breaks in manner already for
transfer to the stigma. Whether the transfer (called pollination) is accomplished by
wind or water or by activities of insect or birds, the important feature here is that
it reaches a ripened stigma, i.e., one that the fully matured and ready for
pollination (Dillon, 1964). Pollination is the process by which pollen is transferred
in plants, thereby enabling fertilization and sexual reproduction. Pollen grains,
which contain the male gametes (sperm) to where the female gamete(s) are
contained within the carpel; in gymnosperms the pollen is directly applied to the
ovule itself. The receptive part of the carpel is called a stigma in the flowers of
angiosperms. The receptive part of the gymnosperm ovule is called themicropyle.
Pollination is a necessary step in the reproduction of flowering plants, resulting in
the production of offspring that are genetically diverse (Marsland, 1964).
Based on the origin of pollen which on the stigma, pollination divided into
several types, that is:
1. Self-pollination . Self-pollination occurs when pollen from one flower
pollinates the same flower or other flowers of the same individual.[9]
It is
thought to have evolved under conditions when pollinators were not
reliable vectors for pollen transport, and is most often seen in short-lived
annual species and plants that colonize new locations. Self pollination may
include autogamy, where pollen moves to the female part of the same
flower (Marsland, 1964).
a. Geitonogamy, when pollen is transferred to another flower on the same
plant. Plants adapted to self-fertilize often have similar stamen and
carpel lengths. Plants that can pollinate themselves and produce viable
offspring are called self-fertile. Plants that cannot fertilize themselves
are called self-sterile, a condition which mandates cross pollination for
the production of off spring (Marsland, 1964).
b. Cleistogamy: is self-pollination that occurs before the flower opens.
The pollen is released from the anther within the flower or the pollen
on the anther grows a tube down the style to the ovules. It is a type of
sexual breeding, in contrast to asexual systems such as 12pomixes.
Some cleistogamousflowers never open, in contrast
to chasmogamous flowers that open and are then pollinated.
Cleistogamous flowers by necessity are self-compatible or self-fertile
plants. Many plants are self-incompatible, and these two conditions are
end points on a continuum (Marsland, 1964).
2. Cross-pollination, also called allogamy occurs when pollen is delivered to
a flower from a different plant. Plants adapted to outcross or cross-
pollinate often have taller stamens than carpels or use other mechanisms to
better ensure the spread of pollen to other plants' flowers (Marsland,
1964).
3. Hybridization is pollination between flowers of different species, or
between different breeding lines or populations. (Marsland, 1964)
Pollination syndromes are suites of flower traits that have evolved in response
to natural selection imposed by different pollen vectors, which can be abiotic
(wind and water) or biotic, such as birds, bees, flies, and so forth. These traits
include flower shape, size, colour, odour, reward type and amount, nectar
composition, timing of flowering, etc. For example, tubular red flowers with
copious nectar often attract birds; foul smelling flowers attract carrion flies or
beetles, etc.(Curtiz, 1968)
1. Wind pollination (anemophily)
Flowers may be small and inconspicuous, green and not showy. They produce enormous
numbers of relatively small pollen grains (hence wind-pollinated plants may beallergens,
but seldom are animal-pollinated plants allergenic). Their stigmas may be large and
feathery to catch the pollen grains. Insects may visit them to collect pollen; in some
cases these are ineffective pollinators and exert little natural selection on the flowers,
but there are also examples of ambophilous flowers which are both wind and insect
pollinated .(Curtiz, 1968)
2. Water pollination (hydrophily)
Water-pollinated plants are aquatic and pollen is released into the water. Water
currents therefore act as a pollen vector in a similar way to wind currents. Their flowers
tend to be small and inconspicuous with lots of pollen grains and large, feathery stigmas
to catch the pollen. However, this is relatively uncommon (only 2% of pollination is
Hydrophily) and most aquatic plants are insect-pollinated, with flowers that emerge into
the air .(Curtiz, 1968)
3. Animal mediated pollination (zoidiophyly, zoidiogamy). Pollination is taking
place because there is the influence of animals as intermediaries. Pollination
usually occurs in plants that have characters as follows (Curtiz, 1968).
a. Having attractive colors
b. Produce something interesting or food animal
c. Pollen is often lumpy and sticky, so sticky to the bodies of animals that
visit flowers
d. Sometimes having a special shape, so the flowers can be visited by
certain animal species
Based on any class of animals that play a role in pollination, zoidiogamy can be
distinguished in (Dillon, 1964):
1. Insect-mediated pollination (entomophyly, entomogamy), for example
butterfly, bees, flies, etc.
2. Birds-mediated pollination (ornithophyly, ornitogamy)
3. Bats-mediated pollination (chiropterophyly, chiropterogamy)
4. Slugs-mediated pollination (malacophyly, malacogamy)
6. Fertilization
The pollen grains (microspores) are haploids cells, which are formed in the
anthers as a result of meiosis, from diploids microsphore mother cells
(microsporocytes). Each pollen grains is destined to grow into a gametophyte―in
this case, a male gametophyte. Such a development normally occurs only when
the mocrospore falls into the sugary secretion of a stigma of the same species,
although pollen grains can often be induced to germinate in artificial solution. The
male gametophyte, which is commonly called the pollen tube, now grows
downward through the tissue of the stigma and the style, deriving nourishment
and protection from these tissue. At maturity, when it penetrates an ovule and
approaches the egg cell, the male gametophyte consist of only three cells―or
rather consist of trinucleate syncytium. One of three nuclei is the tube nucleus,
which regulates the growth of the pollen tube; and the other two are sperm niclei.
One of these sperm nuclei unites with egg, forming the zygote, while the other
unites with both endosperm nuclei, forming a triploid endosperm cell. The process
called fertilization (Marsland,1964).
Fertilization occurs when a sperm nucleus leaves a pollen tube and fuses with an
egg nucleus. After fertilization, the zygotes multiplies by mitosis, and growing at
the expense of the surrounding endosperm tissue, it produces mass of diploid cells
that represents the embryo sporophyte (Marsland, 1964).
While the embrio is growing, many changes also occur in the several tissue, which lies in
direct contact with the embryo and provides it with organic food. The ovule taken as a
whole, become the seed and the ovule chamber also taken as a whole , enlarges and
becomes a fruit (Curtiz, 1968)
Conclution
Inflorescence should be distinguished from the branch that supports some of
flowers in axillary, but not easy to distinguish a compound interest from the
branch that has the flowers in axillary leaves. Inflorescence is one of two types
flowering in plants. Flower used to support produce fruits and seeds, trough the
pollination even and then fertilization.
REFERENCES
Curtis, Helena.1968. Biology. New York: Worth Publishers.
Dillon, Lawrence S.. 1964. The Science Of Life. New York: The Macmillan Company.
Marsland, Douglas. 1964. Principles Of Modern Biology. New York: Holt, Rinehart and Winston.
Sengupta, Saptacee. Pollination vs Fertilization. http//:www.buzzelus.
http://www.buzzle.com/articles/pollination-vs-fertilization.html. diakses 01 juni
2010.
Stein, Sammy. Pollination and fertilization in the gymnosperm.
Http://www.helium.com/items/1923324-pollination-and-fertilization-in-the-
gymnosperm. 01 Juni 2010
Tjitrosoepomo, Gembong. Morfologi Tumbuhan. Yogyakarta: Gadjah mada
university press. 2009.