PLANT EMBRIOLOGY AND REPRODUCTION

“ MONOCOT PLANT “

2nd group of Biology-sbi 2009

Chandra Adi P K 4309020

Ika Ratnasari P K 4309038

Nurhayati Ike P K 4309059

Raras Anglir A K 4309063

Samuel Agus T K 4309074

TEACHER TRAINING AND EDUCATION FACULTY

SEBELAS MARET UNIVERSITY

SURAKARTA

2011

Flower

Flowers, which are the reproductive structures of an angiosperm and consist of four whorls

of modified leaves (from outside in):

Sepals (sepi = fence in) (which collectively are called the calyx), which are often

small and green but are colored like the petals in tulips and lilies, and which generally

enclose the flower before it opens

Petals (petal = a leaf, spread out, flat) (which collectively are called the corolla)

which are often brightly colored to attract pollinators (insects, birds, etc.) and may be

very simple to highly modified

Stamens (stam(en) = anything standing upright, a thread), the “male” reproductive

organs (they make microspores which turn into male gametophytes), which consist of

a stalk (the filament) and a tip (the anther) where the microspores are produced and

turn into pollen (anthe = flower)

Pistil (note spelling) or carpel (carpo = a fruit), which consists of:

Ovary (ova, ovi = egg)

the bottom end where seeds are produced

Style (styl, stylo = a pillar, stake,

column)

the “stalk” portion

Stigma (stigma = spot)

the outer, sticky tip where pollen

sticks when it lands or is placed

there

Seed Structure

Keep in mind that the ovule in the ovary is what becomes the seed. The integument of

the ovule becomes the seed coat. Inside the integument of the ovule was the embryo sac. The

antipodals and synergids senesce and disintegrate. The central cell united with one sperm cell

to make endosperm...a nutritive tissue that accumulates starch, protein, and fats to provide for

the growth of the embryo. The egg cell of the embryo sac united with the other sperm cell to

make a zygote. The zygote grows and becomes a true embryo inside the integument.

When you have a Dormant Embryo, a Storage Tissue, and a Seed Coat, then you have

a SEED. In some seeds, the endosperm is retained as the storage tissue. In other seeds the

endosperm is more or less used up to put storage chemicals into the embryo itself (commonly

in the cotyledons). Below are diagrams and a photo of some seeds.

Germination of Seeds

When grass seeds — like corn (maize) or oats (shown here) — germinate,

the primary root pierces the seed (and fruit) coverings and grows down;

the primary leaf of the plant grows up. It is protected as it pushes up through the soil by

the coleoptile — a hollow, cylindrical structure.

Once the seedling has grown above the surface, the coleoptile stops growing and

the primary leaf pierces it.

Embryogenesis of Monocot Plants

Monocot embryo development at the complete can be seen in Najas. The asymmetric

zygote divides transversely to form a smaller apical cell and large basal cell. Basal cell

enlarged without a single cell divides to form the haustorium. All embryos derived from

apical cell. Tues aoikal split crosswise into 2 cells (c and d). Tues d divides the transverse (m

and ci) to form 4-cell embryo stage (tetrad) is linear (Fig. 3 B). In the cell c and m there is

double vertical division to form 2 rows of cells each 4 pieces of the cell (Figure 3.c). Q

Section consists of 4 cells called quadran. Q splitting Quadran perklinal outer cells will form

4 dermatogen around 4 cells (Figure 3 .. E). Cells on row m and a vertical split lengthwise,

then formed proembrio globular stage (Figure 3. F).

Proembrio become oval-shaped, the middle form the beginner plerom (Gambar3. G).

Q In the division which occurred faster than adjoining cells, which convert the proembrio

symmetry. Rapid growth in the series q form a single cotyledon. (Figure 3. H). The other side

of slow growth, and grow into beginner epicotyl / initial apex (Figure 3. I).

Fruit

Fruit, which is a ripened (mature) ovary (in which seeds develop/are found) and which

serves as protection and means of dispersal for the seeds various types of fruits include:

Simple fruits arise from one ovary in one flower. Examples include cucumber,

peapod, walnut, tomato, orange, cherry, apple, dandelion, and maple “helicopter.”

There are a number of types of simple fruit, each with its own official name.

Aggregate fruits arise from several ovaries in one flower. Examples include

raspberry and strawberry.

Multiple fruits arise from ovaries in several, tightly-clustered flowers which grow

together into one “fruit.” Examples include pineapple, mulberry, and breadfruit.

Angiosperms have alternation of generations with the 2n sporophyte being the dominant

generation. The anthers, which are the equivalent of microsporangia, produce microspores by

meiosis, and the microspores develop into male gametophytes (= pollen).

The ovaries, which are the equivalent of megasporangia, produce megaspores which grow

into female gametophytes, each of which then produces an egg.

Note that technically the “sex organs” of a plant aren’t because they produce spores

(micro- or mega-) which turn into male or female gametophytes. The gametophytes bear the

true sex organs, such as they are, and are where eggs or sperm are actually produced.

By some means (wind or an animal pollinator), the pollen is transferred to the stigma of

the pistil, and a pollen tube grows down into the ovary. Eventually, two sperm nuclei travel

down the pollen tube. Pollination is the transfer of the male gametophyte (pollen) to the

stigma of the female, while fertilization is when the sperm nucleus and egg nucleus unite

Angiosperms have an

unusual thing called double

fertilization. When the sperm

nuclei reach the female

gametophyte, one sperm

nucleus and the egg cell unite

to form a new 2n zygote

(which grows into an embryo). The other sperm nucleus and two nuclei from the female

gametophyte join to form 3n endosperm which often serves as food for the embryo.

The embryo sporophyte consists of:

1. one or two nutrient-storage areas called cotyledons which are in contact with (and

absorb nutrients from) the 3n endosperm. Seeds of some species store their nutrients

primarily in the endosperm, having very small cotyledon(s), while others have most of

their nutrients stored in their cotyledons and the endosperm is very small.

2. the epicotyl (epi = upon, over), which is the region above the cotyledon(s), and which

will become the stem and leaves,

3. the hypocotyl (hypo = under, beneath), which is the region under the cotyledon(s).

The lower end of the hypocotyl, which becomes the root system, is called

the radicle (radix = root) and will become the roots.

In general, monocots tend to store food in their endosperms, and nutrients are transferred

to the cotyledon only as needed. In contrast, many (not all) dicots tend to store food in their

cotyledons with the endosperm being reduced to a papery coating around the embryo.

The characters which distinguish the classes.

Despite the problems in recognizing basal angiosperm taxa, the standard distinctions

between dicots and monocots are still quite useful. It must be pointed out, however, that there

are many exceptions to these characters in both groups, and that no single character in the list

below will infallibly identify a flowering plant as a monocot or dicot.

The table summarizes the major morphological differences between monocots and

dicots; each character is dicussed in more detail below. For more information, refer to the

page on monocot morphology.

MONOCOTS DICOTS

Embryo with single cotyledon Embryo with two cotyledons

Pollen with single furrow or pore

Pollen with three furrows or pores

Flower parts in multiples of three

Flower parts in multiples of four or five

Major leaf veins parallel Major leaf veins reticulated

Stem vacular bundles scattered Stem vascular bundles in a ring

Roots are adventitious Roots develop from radicle

Secondary growth absent Secondary growth often present

Number of cotyledons -- The number of cotyledons found in the embryo is the actual

basis for distinguishing the two classes of angiosperms, and is the source of the names

Monocotyledonae ("one cotyledon") and Dicotyledonae ("two cotyledons").

The cotyledons are the "seed leaves" produced by the embryo. They serve to absorb

nutrients packaged in the seed, until the seedling is able to produce its first true leaves

and begin photosynthesis.

Pollen structure -- The first angiosperms had pollen with a single furrow or pore

through the outer layer (monosulcate). This feature is retained in the monocots, but

most dicots are descended from a plant which developed three furrows or pores in its

pollen (triporate).

Number of flower parts -- If you count the number of petals, stamens, or other floral

parts, you will find that monocot flowers tend to have a number of parts that is

divisible by three, usually three or six. Dicot flowers on the other hand, tend to have

parts in multiples of four or five (four, five, ten, etc.). This character is not always

reliable, however, and is not easy to use in some flowers with reduced or numerous

parts.

Leaf veins -- In monocots, there are usually a number of major leaf veins which run

parallel the length of the leaf; in dicots, there are usually numerous auxillary veins

which reticulate between the major ones. As with the number of floral parts, this

character is not always reliable, as there are many monocots with reticulate venation,

notably the aroids and Dioscoreales.

Stem vascular arrangement -- Vascular tissue occurs in long strands called vascular

bundles. These bundles are arranged within the stem of dicots to form a cylinder,

appearing as a ring of spots when you cut across the stem. In monocots, these bundles

appear scattered through the stem, with more of the bundles located toward the stem

periphery than in the center. This arrangement is unique to monocots and some of

their closest relatives among the dicots.

Root development -- In most dicots (and in most seed plants) the root develops from

the lower end of the embryo, from a region known as the radicle. The radicle gives

rise to an apical meristem which continues to produce root tissue for much of the

plant's life. By contrast, the radicle aborts in monocots, and new roots

arise adventitiously from nodes in the stem. These roots may be called prop roots

when they are clustered near the bottom of the stem.

Secondary growth -- Most seed plants increase their diameter through secondary

growth, producing wood and bark. Monocots (and some dicots) have lost this ability,

and so do not produce wood. Some monocots can produce a substitute however, as in

the palms and agaves.