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class today?
- Reflect for a minute.
Plant Organ System
Grieza J. Apao
Biol 1 Instructor
Plant Body Organization
Plant Organ Systems
Vascular plants have two distinct organ systems:
● The shoot system consists of stems, leaves, and the
reproductive parts of the plant (flowers and fruits).
The shoot system generally grows above ground,
absorbing the light needed for photosynthesis.
● The root system, which supports the plants and
absorbs water and minerals, is usually underground.
The Root System
The roots of seed plants have three major functions:
● anchoring the plant to the soil;
● absorbing water and minerals and transporting
them upwards; and
● storing the products of photosynthesis.
The Root System cont.
Root systems are mainly of two types:
● Taproot systems have a main root that grows down
vertically, and from which many smaller lateral roots
arise. Tap roots penetrate deep into the soil and are
advantageous for plants growing in dry soils. Tap
roots are typical of dicots such as dandelions.
The Root System cont.
Root systems are mainly of two types:
● Fibrous root systems are located closer to the
surface and have a dense network of roots. Fibrous
root systems can help prevent soil erosion. Fibrous
roots are typical of monocots such as grasses.
The Shoot System
The stems and leaves make up the shoot system.
● Stems
- main function is to provide support to the plant,
holding leaves, flowers, and buds.
- they also connect the roots to the leaves, transporting
absorbed water and minerals from the roots to the rest
of the plant, and transporting sugars from the leaves
(the site of photosynthesis) to desired locations
throughout the plant.
The Shoot System cont.
● Plant stems, whether above or below ground, are characterized
by the presence of nodes and internodes.
● Nodes are points of attachment for leaves and flowers.
● Internodes are the regions of the stem between two nodes.
● Apical meristem give rise to the primary plant body and are
responsible for the extension of the roots and shoots.
● Apical bud is where new plant growth and elongation occur.
● An axillary bud is usually found in the area between the base of
a leaf and the stem where it can give rise to a branch or a flower.
The Shoot System cont.
● Leaves are the main
sites for
photosynthesis: the
process by which
plants synthesize
food.
Plant Tissues
Plant tissue systems fall into one of two general types:
meristematic tissue, and permanent (or non-meristematic)
tissue.
● Meristematic cells are undifferentiated and continue to divide
and contribute to the growth of the plant.
● Permanent tissue consists of plant cells that are no longer
actively dividing.
Plant Tissues cont.
Plant Tissues cont.
Plant Tissues
● Secondary meristems (lateral meristems)
- result in secondary growth, a woody increase in girth.
- in stems, vascular cambium arises from procambium cells of
the vascular bundles and parenchyma cells between vascular
bundles.
- The vascular cambium gives rise to the secondary phloem
and secondary xylem.
Plant Tissues
Plant Tissues
Meristems differentiate into three main tissue types:
● Dermal tissue
- covers and protects the plant, and controls gas exchange and water
absorption (in roots).
- Stomata are specialized pores that allow gas exchange through holes in
the cuticle.
- Root hairs, which are extensions of root epidermal cells, increase the
surface area of the root, greatly contributing to the absorption of water and
minerals.
- Trichomes, or small hairlike or spikey outgrowths of epidermal tissue,
may be present on the stem and leaves, and aid in defense against
herbivores
Plant Tissues
● Vascular tissue
- transports water, minerals, and sugars to different parts of the plant.
- is made of two specialized conducting tissues:
Xylem tissue transports water and nutrients from the roots to different
parts of the plant, and also plays a role in structural support in the stem.
Phloem tissue transports organic compounds from the site of
photosynthesis to other parts of the plant. The xylem and phloem always
lie adjacent to each other in a vascular bundle.
Plant Tissues
● Ground tissue (also called the fundamental tissue system)
- fills in the spaces in the plant body between the dermal and vascular
tissues;
- Ground tissue is typically primary tissue and can be found primarily in the
following regions of the plant body: cortex, pith, mesophyll.
- three types of ground tissue: parenchyma, collenchyma, and
sclerenchyma
Plant Tissues
Plant Cell types
Each plant tissue type is comprised of specialized cell types that carry out vastly different functions:
● Vascular tissue cells:
○ Tracheids
○ Vessel elements
○ Sieve tube cells
○ Companion cells
● Dermal tissue cells:
○ Epidermal cells
○ Stomata or more accurately, guard cells
○ Trichomes
● Ground tissue cells:
○ Parenchyma
○ Collenchyma
○ Sclerenchyma
