Systems in Plants
Plants – including mosses, ferns, conifers, and flowering plants – are
multicellular organisms. Plants have two obvious distinguishing
features: They are typically green in colour, and they cannot move
from place to place. Their green colour is caused by chlorophyll – a
chemical that plants use to photosynthesize. They all have
structures – usually roots – to anchor them firmly in one place.
These two features have a profound influence on the overall
structure and functioning of plants.
The structures of flowering plants will be focussed on. Other plants,
such as mosses, ferns, and coniferous trees, have different
structures.
The plant body is divided into two main “body systems.” This
contrasts strikingly with animals, which are made up of many
systems.
Plants perform photosynthesis to make their own food. This means
that they do not need to move around in search of food. As a direct
consequence, they have no need for the complex and coordinated
organ systems found in animals. A plant does not require a digestive
or musculoskeletal system or a nervous system to sense its
surroundings and coordinate movements. However, plants do have
to perform many of the same functions as animals:
 Plants need to exchange gasses with their surroundings.
 They require an internal transportation system to move water
and nutrients around within their bodies.
 They must have a way of reproducing.
The flowering plant body has two main body systems: the root
system and the shoot system. These systems consist of a number of
structures.
The root system is made up of one or more separate roots, whereas
the shoot system consists of the stem, leaves, and flowers (when
present). Plant parts are made up of a wide variety of specialized
cells. As in animals, groups of similar specialized cells are called
tissues. In addition to the plant’s two main body systems, scientists
also refer to their tissues as belonging to separate systems. There
are three main types of plant tissue systems: the dermal tissue
system, the vascular tissue system, and the ground tissue system.
The dermal tissue system is made up of tissues that form the outer
surfaces of plant parts.
The vascular tissue system is made up of tissues specialized for the
transportation of water, minerals, and nutrients throughout the
plant.
The tissues in the ground tissue system make up all of the other
structures within a plant.
THE ROOT SYSTEM
The part of the plant that typically grows below ground. The root
system anchors the plant, absorbs water and minerals from the soil,
and stores food. Most of the water and minerals obtained by the
plant are absorbed by root hairs: fine extensions of dermal tissue
cells.
A plant’s root system can spread underground to cover a very large
area. Some roots even appear above ground or above water. Other
roots, such as radishes and carrots, are specialized for nutrient
storage.
Roots have long been a useful source of foods (sweet potatoes,
carrots, sugar beet), flavourings (liquorice, ginger), fibres (used in
basketry), and a variety of natural remedies.
THE SHOOT SYSTEM
The system that is specialized for two main functions: To conduct
photosynthesis and to produce flowers for sexual reproduction. The
shoot systems of flower plants are made up three parts – the leaf, the
flower, and the stem – which all have distinctive functions
THE LEAF
The main photosynthetic structure of the plant. In photosynthesis,
tissues in the leaf use carbon dioxide, water, and light energy to
produce glucose (a form of sugar) and oxygen. The glucose is used
for plant growth, cellular respiration, and energy storage.
Light Energy + CO2 + H2O  C6H12O6 + O2
The cell structure that actually performs photosynthesis is an
organelle called a chloroplast. Chloroplasts contain flat, disc-like
structures called thylakoids. Thylakoids are arranged in stacks
called grana. These stacks act as solar collectors, using chlorophyll
in the membranes of the thylakoids.
Some leaves are also adapted for support, protection, reproduction,
and attraction. We use leaves in a variety of ways. Many are edible,
such as lettuce, spinach, onion, tea, and herbs. Others are sources
of waxes and medicines.
THE FLOWER
Flowers are specialized structures developed for sexual
reproduction. They contain male or female reproductive structures
or sometimes both. Male reproductive structures produce pollen
grains; female reproductive structures produce eggs. Eggs are
fertilized by pollen. After pollination, the female flower parts form
seeds. In most flowering plants, the seeds are contained within a
specialized structure called a fruit.
Pollination occurs with the help of wind or animals. Flowering plants
such as grasses and many common tree species are wind pollinated.
The flowers are small and drab but produce large amounts of pollen.
In contrast, other flowering plants are pollinated by animals, such as
insects, bats, and birds. These plants often have large, colourful,
and fragrant flowers to attract their would-be pollinators. Most also
produce nectar as an added form of attraction.
Flowers, and the seeds and fruits that come from them, are very
important sources of food and flavourings. Rice, wheat, corn, vanilla,
chocolate, coffee, bananas, apples, mangos, cotton, and even some
medicines all originate from flowers.
THE STEM
The flowering plant stem (or trunk in the case of trees) has several
functions. It supports the branches, leaves, and flowers and
provides a way to transport materials. The stem contains significant
amounts of vascular tissue for carrying substances to and from
roots, leaves, flowers, and fruits.
Some stems are specialized for food storage, protection,
photosynthesis, and reproduction. Plant stems provide us with
sugar, potatoes, wood, and paper products, cork, linen and a variety
of medicines