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A Closer Look at Plants
A
plant is a living thing. This means that plants
reproduce, grow and feed. Plants live on water,
air, and sunlight.
Plants
are broken into two main groups, flowering and
non-flowering.
- Flowering
Plants - Most of the plants around us
are flowering plants. Flowering plants have
roots, stems, leaves, flowers and fruits.
- Non-
flowering Plants - These do not have flowers
and include plants like algae, ferns, fungi
and mosses.
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| Parts
of a Plant |
 In
order to discuss plants in a meaningful way, it
is important to know the proper names for the
all the different parts a plant can have. Flowering
plants have four major part types:
- Leaves
Leaves make all the food for the plant. They
do this by changing light, water and gases
into food. This process is called photosynthesis.
-
Stems
and branches
Stems and branches hold up the leaves and
space the leaves out. This helps the plant
to get the light it needs.
-
Roots
Roots help fix the plant to the soil or
to other plants. Roots take in water and
nutrients.
-
Flowers
Flowers contain the male and female parts
of the plants. Successful pollination of
the flower can result in the production
of fruit and seeds.
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| Roots |
All
roots are responsible for:
-
anchoring the plant to the ground
- extracting
water and minerals from the soil
 In
a typical root we can distinguish the following
parts:
1.
Primary root - the thickest . It grows
downwards.
2.
Secondary roots - arise from the primary
root. They are not as thick as the primary one.
They go sidewards.
3.
Root cap - is a kind of protection the
roots end with. It is designed to drill the
soil and it is able to guide the root growth
by perceiving gravity.
4.
Root hairs - are minute filaments roots
are covered with. They absorb water and nutrients
from the soil.
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Stems
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All
stems are responsible for:
-
supporting leaves and flowers physically
- holding
the leaves and flowers in the best position
for food gathering and reproduction
- using
xylem and phloem to transport materials from
areas of plenty to areas of need in various
parts of the plant
- storing
nutrients for future use
 bud
- an
underdeveloped and unelongated stem composed
of a short axis with compressed internodes,
a meristematic apex, and primordial leaves and/or
flowers.
terminal
bud - a bud at the tip of a stem responsible
for terminal growth.
axillary
bud or lateral bud - buds
along side the axis of a stem; they were produced
by the terminal bud during growth; once they
grow out and form a lateral stem they become
terminal buds of the lateral branch.
flower
bud - a bud containing a floral meristem
which develops into flowers; usually larger
than vegetative buds.
leaf
scar - a scar marking the former point of
attachment of a leaf or petiole to the stem.
internode
- the part of the stem between nodes
node
- part of stem marking the point of attachment
of leaves, flowers, fruits, buds and other stems.
lenticel
- rough areas on stems (and some fruits,
ex. apple) composed of loosely packed cells
extending from the cortex through the ruptured
epidermis; serve as "breathing pores"
for gas exchange. Only occur on young stems.
growth
rings - bud scale scars from the last terminal
bud; they denote flushes of growth (usually
per year). Can be used to age stems because
usually 1 set of growth rings is produced per
year on temperate trees in the Temperate Climatic
Zone.
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 Leaves |
 All
leaves are responsible for:
-
absorbing the sun's rays
- the
majority of photosynthetic production (which
can take place in any green part of a plant),
- taking
in carbon dioxide and releasing oxygen and
water vapor (breathing)
- removing
waste products from the plant
- using
osmotic pressure to draw water up from the
roots
Parts of a leaf
| tip |
the
terminal point of the leaf |
| blade
or lamina |
the
flattened, green, expanded portion
of a leaf. |
| margin |
edge
of a leaf. |
| midrib |
the
most prominent central vein in a leaf.
|
| lateral
veins |
secondary
veins in a leaf. |
| petiole |
the
leaf stalk (connects blade to stem). |
| stipules |
leaf-like
appendages (at the base of petiole of some
leaves). |
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| Photosynthesis |
 Photosynthesis
is
the process in which carbon dioxide (CO2)
and water (H2O) are used to produce
carbohydrates and evolve oxygen (O2)
in the presence of light and chlorophyll; the
net result is light energy (radiant energy) is
converted into chemical energy in the form of
fixed carbon compounds (carbohydrates). |
| Flowers |
|
All
flowers are responsible for one important function:
reproduction.
The
Flower:
The flower is the reproductive unit of some
plants (angiosperms). Parts of the flower include
petals, sepals, one or more carpels
(the female reproductive organs), and stamens
(the male reproductive organs).
The
Female Reproductive Organs:
The pistil is the collective term for the carpel(s).
Each carpel includes an ovary (where
the ovules are produced; ovules are the female
reproductive cells, the eggs), a style
(a tube on top of the ovary), and a stigma
(which receives the pollen during fertilization).
The
Male Reproductive Organs:
Stamens are the male reproductive parts
of flowers. A stamen consists of an anther (which
produces pollen) and a filament. The pollen
consists of the male reproductive cells; they
fertilize ovules.
| Flower
part |
Part
function |
| Petal |
Petals are used to attract insects into the flower, they may have
guidelines on them and be scented. |
| Stigma |
Is covered in a sticky substance that the pollen grains will adhere
to. |
| Style |
The style raises the stigma away from the Ovary to decrease the likelihood
of pollen contamination. It varies in length. |
| Ovary |
This protects the ovule and once fertilisation has taken place it
will become the fruit. |
| Ovule |
The Ovule is like the egg in animals and once fertilisation has taken
place will become the seed. |
| Receptacle |
This is the flower's attachment to the stalk and in some cases becomes
part of the fruit after fertilisation e.g.
strawberry. |
| Flower stalk |
Gives support to the flower and elevates the flower for the insects. |
| Nectary |
This is where a sugary solution called nectar is held to attract
insects. |
| Sepal |
Sepals protect the flower whilst the flower is developing from a
bud. |
| Filament |
This is the stalk of the Anther. |
| Anther |
The Anthers contain pollen sacs. The sacs release pollen on to the
outside of the anthers that brush against
insects on entering the flowers. The pollen
once deposited on the insect is transferred
to the stigma of another flower or the same
flower. The ovule is then able to be fertilised.
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|
| Pollination |
 Pollen
must fertilize an ovule to produce a viable seed.
This process is called pollination, and is often
aided by animals like bees, which fly from flower
to flower collecting sweet nectar. As they visit
flowers, they spread pollen around, depositing
it on some stigmas. After a male's pollen grains
have landed on the stigma during fertilization,
pollen tubes develop within the style, burrowing
down to the ovary, where the sperm fertilizes
an ovum (an egg cell), in the ovule. After fertilization,
the ovule develops into a seed in the ovary.
Most
flowering plants (ninety percent) depend on
animals to make the vital pollen-grain delivery.
The remaining flowering plants rely on wind
and some-times splashing raindrops to ferry
pollen, but this is a less precise method. Pollinating
animals do the job for a reward: food, usually
in the form of nectar.
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| Fruit
and Seeds |
| The
fruit is that part of a plant which is in charge
of protecting the seeds and guarantee their dispersal.
It becomes as a result of the fertilization inside
the carpel, which produce the ripening of the
ovary walls that will create the fruit. Some fruits,
however, have another origin, deriving from the
flower receptacle or some other parts of the flower.
We
have many kinds of fruits but the most typical
fruit shows the following parts:
-
The pericarp is the external part of
a fruit. It is all that surrounds the seed.
It is divided into:
-
The exocarp is the outer covering.
In an apple, for instance, it is what we know
as the "skin".
-
The mesocarp is the middle covering.
In a peach what we ordinary call the "flesh".
-
The endocarp is the inner covering
, in many cases the stiffened part normally
covering the seed. In a plum , for example,
what we commonly know as the "stone".
Types
of Fruit
There
are many different types of fruit that we can
eat:
- Soft
fruits, eg raspberry, blackberry, redcurrant,
strawberry, bilberry.
- Citrus
fruits, eg orange, lime, lemon, kumquat, grapefruit.
- Stone
fruits, plum, apricot, peach, lychee, cherry,
mango.
- Fleshy
fruits, eg apple, papaya, pineapple, pear,
banana
- Vine
fruits, eg grape, water melon, cantaloupe
Seeds
 The
seed is enclosed inside the endocarp.This is
a typical seed. We can see the following parts:
-
The radicle is the part of the embryo
which emerges first. Once outside it develops
into a main root, producing root hairs and
secondary roots.
- -
The plumule is like a leaf in its early
development.
- -
The hypocotyl is the space between
the radicle and the plumule. It develops into
a stem.
- The
endosperm is the food supply contained
in the seed. This is sometimes included in
the cotyledons, which either achieve the function
of primary leaves or food storage, even both
of them in some cases.
- According
to the number of cotyledons, we classify plants
in two groups: monocotyledons or monocots
and dicotyledons or dicots.
In the first group we find so important plants
as cereals, palms, lilies, tulips or orchids.
The members of the second group are more numerous
and comprises most of the trees and flowers.
- The
seed coat or testa - is the
outer layer of the seed.
- The
micropyle is a litle pore on the seed
coat , through which, apart from entering
the sperm, the seed absorbs water to begin
germination.
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| Dangerous
Plants |
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 A
plant is carnivorous if it attracts, captures,
and kills animal life forms. It must also digest
and absorb the nutrients from the prey to qualify
as a carnivorous plant. Carnivorous plants are
just like other plants, except they have a toolbox
of abilities that, altogether, allow the plant
to be carnivorous. Other plants have a few of
these tools, but not all of them. The main tools
are the abilities to attract insects, capture
them, kill them, digest them, and absorb the
resulting nutrients.
source:
http://collections.ic.gc.ca; http://www.learnz.org.nz;
http://generalhorticulture.tamu.edu
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caribbeanedu.com
