functions of xylem and phloem cells + more

1. Types of Reducing Sugars
All monosaccharides (simple sugars that can't be broken down into smaller molecules)
are reducing sugars. Two of three types of disaccharides (sugars with two chemical
rings), maltose and lactose, have the open chemical structure needed to act as reducing
agents. The simple structure of monosacchrides allows them to be broken down twice as
quickly as disaccharides, while disaccharides must be broken into their smaller parts
first.
Types of Non-Reducing Sugar
The third type of disaccharides, sucrose, and polysaccharides (sugars with multiple
chemical rings) are non-reducing sugars. Polysaccharides--starches--have closed
structures, which use free atoms to bond together their multiple rings, and take a much
longer time to be broken down.
Compare the function and structure of starch and lipids.
Lipids are composed of glycerol and fatty acids .Starches are composed of
monosaccharides.
Carbohydrates and lipids can both be used as energy storage however carbohydrates are
usually used for short term storage whereas lipids are used for long term storage. Due to
lipids having less number of oxygen than in carbohydrates a lipid gives you twice as much
energy as a carbohydrate Carbohydrates are soluble in water unlike lipids. This makes
carbohydrates easy to transport around the body (from and to the store). Also,
carbohydrates are a lot easier and more rapidly digested so their energy is useful if the
body requires energy fast. As for lipids, they are insoluble which makes them more difficult
to transport however because they are insoluble, lipids do not have an effect on osmosis
which prevents problems within the cells in the body. They also contain more energy per
gram than carbohydrates which make lipids a lighter store compared to a store of
carbohydrates equivalent in energy. Lipids constitute the bilayer, which is not the case
with starch.
Palisade cells Function
Nucleus- control center of cell. Stores gentic information
Cell wall- Protects cell and keeps it rigid.
Cell membrane- Allows things to enter and exit the cell.
Vacuole- Bag of liquid that keeps cells shape.
Cytoplasm- Jelly-like substance which things dissolve in.
Chloroplast- A green substance that collects sunlight for photosynthesis

2. These are the things that plants need for photosynthesis:
carbon dioxide
water
Light
glucose
oxygen
We can show photosynthesis as this word equation: carbon dioxide + water (+ light energy) -->
glucose + oxygen (Light energy is shown in brackets because it is not a substance.)
This is the symbol equation for photosynthesis:
Where does this process take place in the plant?
Photosynthesis takes place in the chloroplasts in plant cells. Chloroplasts contain a green
substance called chlorophyll. This absorbs the light energy needed to make photosynthesis
happen. Plants can only photosynthesise in the light.

3. Palisade cells in leaves have lots of chloroplasts
Plants get carbon dioxide from the air through their leaves, and water from the ground through
their roots.
Light energy comes from the sun.
The glucose produced can be turned into other substances, such as starch, which is used for
storage. The oxygen produced is released into the air from the leaves.
Demonstrating photosynthesis
Animals eat to get food, but green plants make their own food. The process plants use is called
photosynthesis. We say that plants can photosynthesise.
These are the things that plants need for photosynthesis:
carbon dioxide
water
lightThese are the things that plants make because of photosynthesis:
glucose
oxygen
We can show photosynthesis as this word equation:
carbon dioxide + water (+ light energy) --> glucose + oxygen
(Light energy is shown in brackets because it is not a substance.)

4. Where does this process take place in the plant?
Photosynthesis takes place in the chloroplasts in plant cells. Chloroplasts contain a green
substance called chlorophyll. This absorbs the light energy needed to make photosynthesis
happen. Plants can only photosynthesise in the light.
Palisade cells in leaves have lots of chloroplasts
Plants get carbon dioxide from the air through their leaves, and water from the ground through
their roots.
Light energy comes from the sun.
The glucose produced can be turned into other substances, such as starch, which is used for
storage. The oxygen produced is released into the air from the leaves.
Palisade cells are cells found within the mesophyll in leaves of dicotyledonous plants. Palisade cells have
a lot of extra chloroplasts to help with photosynthesis, they are mostly found in the top surfaces of the
leaves. They contain chloroplasts, which convert the energy in light to chemical energy through
photosynthesis. The cylindrical shape of palisade cells allows a large amount of light to be absorbed by
the chloroplasts. Beneath the palisade mesophyll are the spongy mesophyll cells, irregularly-shaped cells
that having many intercellular spaces to allow the passage of gases, such as the intake of carbon dioxide
for photosynthesis to take place. The stomata is the way in which these gases are exchanged, as well as
the transpiration of water from the xylem, either by the apoplast or symplast pathway. Palisade cells are
positioned towards the upper surface of the leaf and contain the largest number of chloroplasts per cell
in plants. This makes them the primary site of photosynthesis in a plant's leaves. They have a very large
surface area in order for them to absorb more light during photosynthesis.This makes photosynthesis
easier and more chemical energy can be produced for the plant. Palisade cells are found in leaves, they

5. make plants yellow. palisade cell use the light energy to turn carbon dioxide and water into glucose and
oxygen
FUNCTIONS
Cuticle-The cuticle is a waxy layer covering plants. its function is to lessen water loss by not letting it
diffuse out so easily.
Plant cuticles are a protective waxy covering produced only by the epidermal cells [1] of leaves, young
shoots and all other aerial plant organs without periderm. The cuticle tends to be thicker on the top of the
leaf, but is not always thicker in xerophytic plants living in dry climates than in mesophytic plants from
wetter climates, despite a persistent myth to that effect. In addition to its function as a permeability barrier
for water and other molecules, the micro and nano-structure of the cuticle confer specialised surface
properties that prevent contamination of plant tissues with external water, dirt and microorganisms. Many
plants, such as the leaves of the sacred lotus (Nelumbo nucifera) exhibit ultra-hydrophobic and self-
cleaning properties that have been described by Barthlott and Neinhuis (1997).[8] The lotus effect has
potential uses in biomimetic technical materials.
"The waxy sheet of cuticle also functions in defense, forming a physical barrier that resists penetration by
virus particles, bacterial cells, and the spores or growing filaments of fungi
Epidermis
The epidermis is the outer layer of cells covering the leaf. It forms the boundary separating the plant's
inner cells from the external world. The epidermis serves several functions: protection against water loss
by way of transpiration, regulation of gas exchange, secretion of metabolic compounds, and (in some
species) absorption of water. Most leaves show dorsoventral anatomy: The upper (adaxial) and lower
(abaxial) surfaces have somewhat different construction and may serve different functions.
The epidermis is usually transparent (epidermal cells lack chloroplasts) and coated on the outer side with
a waxy cuticle that prevents water loss. The cuticle is in some cases thinner on the lower epidermis than
on the upper epidermis, and is generally thicker on leaves from dry climates as compared with those from
wet climates.
The epidermis tissue includes several differentiated cell types: epidermal cells, epidermal hair cells
(trichomes) cells in the stomate complex; guard cells and subsidiary cells. The epidermal cells are the
most numerous, largest, and least specialized and form the majority of the epidermis. These are typically
more elongated in the leaves of monocots than in those of dicots.
The epidermis is covered with pores called stomata, part of a stoma complex consisting of a pore
surrounded on each side by chloroplast-containing guard cells, and two to four subsidiary cells that lack
chloroplasts. Opening and closing of the stoma complex regulates the exchange of gases and water vapor
between the outside air and the interior of the leaf and plays an important role in allowing photosynthesis
without letting the leaf dry out. In a typical leaf, the stomata are more numerous over the abaxial (lower)
epidermis than the adaxial (upper) epidermis and more numerous in plants from cooler climates
The upper epidermis is responsible for preventing water loss by evaporation. It does this by having a
waxy cuticle on the top of the leaf.
The lower epidermis has stomata, which allow gases to enter and leave the leaf as a result of
photosynthesis and respiration.

6. Mesophyll
Most of the interior of the leaf between the upper and lower layers of epidermis is a parenchyma (ground
tissue) or chlorenchyma tissue called the mesophyll (Greek for "middle leaf"). This assimilation tissue is
the primary location of photosynthesis in the plant. The products of photosynthesis are called
"assimilates".
In ferns and most flowering plants, the mesophyll is divided into two layers:
An upper palisade layer of tightly packed, vertically elongated cells, one to two cells thick,
directly beneath the adaxial epidermis. Its cells contain many more chloroplasts than the spongy
layer. These long cylindrical cells are regularly arranged in one to five rows. Cylindrical cells, with
the chloroplasts close to the walls of the cell, can take optimal advantage of light. The slight
separation of the cells provides maximum absorption of carbon dioxide. This separation must be
minimal to afford capillary action for water distribution. In order to adapt to their different
environment (such as sun or shade), plants had to adapt this structure to obtain optimal result.
Sun leaves have a multi-layered palisade layer, while shade leaves or older leaves closer to the
soil are single-layered.
Beneath the palisade layer is the spongy layer. The cells of the spongy layer are more rounded
and not so tightly packed. There are large intercellular air spaces. These cells contain fewer
chloroplasts than those of the palisade layer. The pores or stomata of the epidermis open into
substomatal chambers, which are connected to the air spaces between the spongy layer cells.
These two distinct layers of the mesophyll are absent in many aquatic and marsh plants. Even an
epidermis and a mesophyll may be lacking. Instead, for their gaseous exchanges they use a homogeneous
aerenchyma (thin-walled cells separated by large gas-filled spaces). Their stomata are situated at the
upper surface.
Leaves are normally green, due to chlorophyll in plastids in the chlorenchyma cells. Plants that lack
chlorophyll cannot photosynthesize
Chloroplasts
Chloroplasts are tiny, round, green food factories within the leaves of a plant. During
photosynthesis, they use energy from sunlight to turn chemicals in air and water into plant food
Chloroplasts are those subunit in a plant cell, which produce food for a plant through the
process of photosynthesis. Chloroplasts are somewhat similar to mitochondria found in
animal cells which can produce energy. They reproduce by the process of division of cells
and have their own genetic systems. It's the chloroplasts which convert carbon dioxide into
carbohydrates, which are consumed by plants. Moreover amino acids, lipid components and
fatty acids of the cell membranes are synthesized by chloroplasts. In addition to that, they
reduce nitrogen into ammonia and other organic compounds. Once you have got the basic
idea, let's take a look at how they function in a plant cell.

7. Chloroplast Function in a Plant Cell
Chloroplast contain an important component called chlorophyll, which is responsible for
production of food. It's the chlorophyll which gives the chloroplast and in turn, leaves its
characteristic green color. Chlorophyll contained in the chloroplasts is responsible for
absorbing sunlight. It's through the process of photosynthesis that a plant makes food for
itself. The process includes absorbing the energy from the sun so as to create sugar. When
sunlight hits a chloroplast, the chlorophyll in it uses the energy and in combination with
carbon dioxide and water forms sugar and oxygen. Plants use these sugars for survival and
the oxygen released is used by animals to breathe.
Read more at Buzzle: http://www.buzzle.com/articles/chloroplast-function.html
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct
photosynthesis. Chloroplasts capture light energy, store it in the energy storage molecules ATP and
NADPH and use it in the process called photosynthesis to make organic molecules and free oxygen from
carbon dioxide and water.[1]
Chloroplasts are green because they contain the chlorophyll pigment.
(1) Absorption of light energy and conversion of it into biological energy.
(2) Production of NAPDH2 and evolution of oxygen through the process of photosys of
water.
(3) Production of ATP by photophosphorylation. NADPH2 and ATP are the assimilatory
powers of photosynthesis. Transfer of CO2 obtained from the air to 5 carbon sugar in the
stream during dark reaction.
(4) Breaking of 6-carbon atom compound into two molecules of phosphoglyceric acid by the
utilization of assimilatory powers.
(5) Conversion of PGA into different sugars and store as stratch. The chloroplast is very
important as it is the cooking place for all the green plants. All heterotrophs also depend on
plasts for this food.
Phloem and xylem are complex tissues that perform transportation of food and water in a plant.
They are the vascular tissues of the plant and together form vascular bundles. They work
together as a unit to bring about effective transportation of food, nutrients, minerals and water.
VASCULAR BUNDLE
Xylem: tubes that bring water and minerals from the roots into the leaf.
Phloem: tubes that usually move sap, with dissolved sucrose, produced by photosynthesis in the
leaf, out of the leaf.

8. The xylem typically lies on the adaxial side of the vascular bundle and the phloem typically lies on the
abaxial side. Both are embedded in a dense parenchyma tissue, called the pith or sheath, which usually
includes some structural collenchyma tissue.
Phloem Xylem
Function: Transportation of food and Water and mineral transport
nutrients from leaves to from roots to aerial parts of
storage organs and growing the plant.
parts of plant.
Xylemis formed of thick-walled,tubular and often dead cells.The cells are placed end to end like
drain pipes ,and the partitions between the cell dissolve to form long pipelines for the transport
of water and minerals.
Xylem cells transport water and minerals absorbed by the roots from the soil. They transport
them to leaves where glucose is prepared during photosynthesis.
Old Xylem forms wood and does not participate in transport.
Phloem - a protective layer made up of tiny tubes that transport the sugars from the leaves to the rest
of the tree. Phloem carries organic nutrients to all parts of the plant where required. Its mainly
concerned with transport of soluble organic material.
Bundle-sheath cells are photosynthetic cells arranged into tightly packed sheaths around the veins of a
leaf. They form a protective covering on leaf veins, and consist of one or more cell layers, usually
parenchyma. Loosely arranged mesophyll cells lie between the bundle sheath and the leaf surface. The
Calvin cycle is confined to the chloroplasts of these bundle sheath cells in C4 plants.
Cambium- It is responsible for secondary growth. It produces new phloem towards the outside of the
plant and new xylem towards the inside. There are also two kinds of cells, ray initials and fusiform
initials, fusiform initials produce the xylem and phloem. Ray initials produce parenchyma cells that form
rays across the stem and are used in transport between the xylem and phloem. The vascular cambium is
also responsible for producing wood.

9. In plants, the substomatal cavity is the cavity located immediately proximal to the stoma. It acts as a
diffusion chamber connected with intercellular air spaces and allows rapid diffusion of carbon dioxide
and other gases (such as plant pheromones) in and out of plant cells.
Guard Cells- The function of the guard cells are that they help to regulate the rate of transpiration by
opening and closing the stomata thus preventing excessive water loss.
The function of the guard cells is that they help to regulate the rate of transpiration by opening and
closing the stomata. The guard cell opens when there is too much water. It is also adapted for gas
exchange between plants and environment.
For example, it opens during rainy days and closes when the weather is too dry or windy.
They also control the size of the pore.
Use of Guard Cells
The walls surrounding the stoma are very flexible and thin; however, the opposite walls
of stoma are rigid and thicker. Whenever the guard cells are inflated with internal water
pressure, there is a difference in thickness in surrounding walls which results in the
development of an opening. On a hot day, when the guard cells lose water, they deflate
and start pushing toward each other, thus resulting in the closure of the stoma.
Stoma- In botany, a pore (tiny hole) in the epidermis (outer layer of tissue) of a plant. There are lots of
these holes, usually in the lower surface of the leaf. A leaf contains several layers of tissue. The outer
layer is the epidermis and is only one cell thick. Stomata occur in the lower epidermis.
Each stoma is surrounded by a pair of guard cells that are crescent-shaped when the stoma is open but
can collapse to an oval shape, thus closing off the opening between them. Stomata allow the exchange
of carbon dioxide and oxygen (needed for photosynthesis and respiration) between the internal tissues
of the plant and the outside atmosphere.
They are also the main route by which water is lost from the plant (water vapour), and they can be
closed to conserve water, the movements being controlled by changes in turgidity of the guard cells.
At night the stomata may allow oxygen to diffuse in and carbon dioxide out because only respiration is
taking place.
Photosynthesis (photo = light and synthesis = to make) is the process plants use to
change carbon dioxide and water into sugar using sunlight. This sugar, glucose, is their food, and
the process gives off oxygen.

10. Photosynthesis is the conversion of light energy into chemical energy by living organisms. The
raw materials are carbon dioxide and water. The energy source is sunlight, and the end-products
include glucose and oxygen. It is arguably the most important biochemical pathway, since nearly
all life depends on it. It is a complex process occurring in higher plants, phytoplankton, algae, as
well as bacteria such as cyanobacteria. Photosynthetic organisms are also referred to as
autotrophs.
Photosynthesis is the process by which plants, some bacteria, and some protistans use the energy
from sunlight to produce sugar, which cellular respiration converts into ATP, the "fuel" used by
all living things. The conversion of unusable sunlight energy into usable chemical energy is
associated with the actions of the green pigment chlorophyll. Most of the time, the
photosynthetic process uses water and releases the oxygen that we absolutely must have to stay
alive.
We can write the overall reaction of this process as:
6H2O + 6CO2 + light → C6H12O6+ 6O2
6 water molecules + 6 carbon dioxide molecules + light is converted into 1 glucose molecule and
6 oxygen molecules
NaHCO3 supplies dissolved CO2 to the water plant ( = aquatic plant).
The immersion water is enriched by sodium hydrogen carbonate, which releases carbon dioxide
to increase the rate of photosynthesis

11. Three factors can limit the speed of photosynthesis - light intensity, carbon dioxide
concentration and temperature.
Light intensity
Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of
water and carbon dioxide. Increasing the light intensity will boost the speed of
photosynthesis. OR The relationship between light intensity and photosynthetic rate is that if the
intensity of the light is high then the rate of photosynthesis will increase. However the rate of
photosynthesis will only increase to an extent after intensity of light reaches a certain point
photosynthesis rate will stay still.

12. I predict that the more intense the light, the higher the rate of
photosynthesis. Plants need light. Light provides the
energy for photosynthesis to occur. Chlorophyll is an enzyme and it
speeds up the reaction. If a plant does not get enough of either of
these things, photosynthesis will not happen as quickly, if at all.
Therefore, I predict that when the light is not very intense we will
not see so many bubbles being produced. This is because the plant will
not have so much energy (derived from light) to activate
photosynthesis. All reactions require certain activation energy, and
if this is not reached the reaction will occur more slowly. I think
that as we move the lamp away (and therefore reduce the light
intensity) from the pondweed the number of bubbles produced will
decrease steadily. For instance, say at 10cm distance 50 bubbles are
counted, it is likely that at 20cm distance 25 bubbles will be
counted, as the lamp is twice the distance away. This means the rate
of photosynthesis is halved but we are measuring the light intensity
and so this will not mean the rate of photosynthesis is halved. I
think that if we move the lamp any further away than 50cm no bubbles
at all will be produced because there will simply not be enough light
for photosynthesis to work but we are only doing it till 17cm which
will give us enough results.
When I am doing my experiment I will measure the amount of oxygen made
which will be measured by the bubbles.
I will vary the distance apart from the beaker to the lamp. The
equipment I will be using are as follows: a large beaker, a healthy
pondweed plant, a lamp, water, a stopwatch, a pinch of sodium
bicarbonate which will give the plant more carbon dioxide.
6 Suggest another way to measure the rate of photosynthesis.
Record the number of oxygen bubbles given off per unit time.
Record the total volume of oxygen evolved in a fixed interval of time.
9 What precautions should be taken?
any one
Include a heat shield and check its temperature at intervals.
l Make sure the apparatus is air-tight by closing the clip completely.
l Don’t spray water onto the hot light bulb.