Unformatted text preview: What is plant physiology
The science that studies plant function
How do plants obtain their nutrients?
How do they convert solar energy to food?
How do plants survive harsh environments?
How do they respond to hormones and other stimuli?
How do plant reproduce, protect, and nourish their offspring?
How do plant fight to ward off disease-causing microorganisms? Major design elements of plants
1. Convert sunlight into chemical energy
2. Plants are non-motile but are capable of growing towards
3. Terrestrial plants are structurally reinforced to support
their masses (by lignified secondary cell wall)
4. Terrestrial plants have evolved mechanisms to conserve
5. Terrestrial plants are capable of moving water, minerals, &
other essential nutrients The "Typical" Plant Body
The Shoot System
Above ground (usually)
reproduction & dispersal
food and water conduction
the shoot system includes
the reproductive organs:
[flowers and fruits]
The Root System
Anchor the plant in the soil
Absorb water and nutrients
Conduct water and nutrients
Food Storage Unique features of plant cells
Unique The secondary cell wall is made
between the primary cell wall and
the cell membrane The Three Tissue Systems
The (Parenchyma cell) The xylem tissue is a complex tissue comprising of vessel elements,
tracheids, xylem parenchyma cells (transfer cells), and sclerenchyma cells
tracheids The phloem is also a complex tissue containing sieve tube elements,
parenchyma cells (companion cells), and sclerenchyma cells
parenchyma The organization of three different tissues in leaf
The Plant Growth- growth is localized to specific areas called meristems,
which are the sites of repeated cell division of unspecialized cells
These cells differentiate and become specialized in function Leaf primordium
primordium Shoot apical meristem
meristem Apical Meristem gives rise to three primary meristems:
protoderm --epidermal tissue
ground meristem-->ground tissue
procambium-->vascular tissue Root Apical Meristem
Most cell division is directed away from
the root cap
Populations of cells in apical meristem
which reproduce much more slowly than
other meristematic cells
The Zone of Cell Division
Protoderm - outermost primary meristem
Ground meristem - central primary meristem
Procambium - innermost primary meristem
The Zone of Elongation
Cells elongate up to ten times their original
length, pushing the root further downward
into the soil
The Zone of Maturation
Region of the root where completely
functional cells are found
functional Root Cap (derived from the root apical meristem)
protects the delicate apical meristem
secretes polysaccharide slime that lubricates the soil
constantly sloughed off and replaced
constantly Characteristic features of the meristematic cells
1. The cells are capable of undergoing regular, continuous mitotic divisions.
2. The cells are relatively smaller in size compared to mature cells. They are either rectangular or isodiametric in shape.
3. The cells are always compactly arranged, without any intercellular spaces.
4. The cells have a thin cell wall, which is composed of only cellulose.
5. The cells enclose a large amount of clear and transparent cytoplasm.
6. Every cell has a large nucleus, which is situated in the center of the cell.
7. The chromosomes are always found in some phase of mitotic division.
8. Except mitochondria, other cell organelles are either absent or present in a nonfunctional state.
For example, the plastids may be present in a non-functional state called proplastids.
9. Vacuoles are either absent or very small. The formation of lateral roots The pericycle, jjust inside the endodermis,
is a layer of cells that may become meristematic
and divide to form the lateral root.
A lateral root forms as a clump of cells in the
pericycle, then elongates and pushes through
the cortex until it emerges from the primary root.
the Lateral meristems add girth to stems and roots
through secondary growth
through 2nd growth results from two lateral meristems:
vascular cambium and cork cambium
Vascular cambium produces secondary
xylem and phloem
Cork cambium produces a tough, thick
covering for roots and stems that replaces the
View Full Document