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Chapter 20
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Plant anatomy and growth
Plant organ – leaves
- stem
- root
- monocot and eudicot
Plant tissue and cell - apical meristem
– epidermal tissue
- ground tissue – parenchyma
- collenchyma
- sclerenchyma
- vascular tissue – xylem and phloem
Organization of leaves – epidermal tissue
- mesophyll
- stomata
Organization of stems - nonwoody
- woody - vascular cambium
- annual ring
Organization of root Plant nutrition - mineral uptake
Transportation of nutrition – xylem: cohesion-tension model
- pholem : pressure-flow model
生醫系 劉秉慧老師
分機11815
20.1 Plant Organs
• Flowering plants have two major components to
their structure.
– A root system
– A shoot system composed of the stem, leaves,
and reproductive organs.
• At the end of the root and shoot system is a
terminal bud from which vertical growth, called
primary growth, occurs.
• To conduct photosynthesis, leaves need solar
energy, water, and carbon dioxide to generate
carbohydrate.
Plant Organs: Leaves
• structures of photosynthetic leaves
– blade (葉身): the wide part of the leaf
– petiole(葉柄): the stalk connecting leaf to stem.
– Vein: with vascular tissue
• diversity in leaf structure and function
- not all leaves are foliage leaves
- some are specialized to protect the plant, attach
to objects (tendrils), or capture insects
- some trees are called evergreens
- some plants are deciduous(落葉性的): they drop
their leaves during certain seasons.
Leaves diversity
捲鬚
捕蠅草
Plant Organ: Stems (莖)
• The stem is the main axis of the plant.
• On the stem
- apical bud (terminal bud) for primary growth
- lateral buds for side branches
- Nodes(節): the points where leaves attach to stems
- internode (節間): the region between nodes.
• Function - contains the vascular tissue that
transports water and nutrients
- supporting
- photosynthesis
- serve as a storage organ.
Plant Organ: Roots (根)
• Functions of root
- anchor plants to the soil.
- absorb water and mineral from the soil
• The surface area of roots is greatly increased by the
production of root hairs.
• There are different types of root systems.
– single taproot(主根), fibrous root, prop roots (支柱
氣根)
Monocot (單子葉) vs Eudicot (雙子葉) Plants
• Flowering plants are divided into two major groups
based upon the difference in embryonic leaves
(cotyledons).
– monocots (單子葉): Plants with a single cotyledon
including rice, wheat, corn
– eudicots (雙子葉): Plants with two cotyledons,
including a large number of species
• Cotyledons provide developing plants with nutrients
and serve other roles.
Monocot vs Eudicot Plants
• vascular tissue
- serves as a type of circulatory system for plants
- The arrangement differs between monocots and
eudicots.
• The pattern of venation in leaves
– Monocots have parallel venation(平行脈紋).
– Eudicots have a net-like pattern. (網狀)
• The pattern in root
• The pattern in stem
- Monocots: vascular bundles scattered in stem
- Eudicots: vascular scattered in a distinct ring
Monocot Versus Eudicot Plants
Plants have two types of vascular tissue.
The xylem transports water and minerals.
The phloem transports organic nutrients.
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Plant organ – leaves
- stem
- root
- monocot and eudicot
Plant tissue and cell - apical meristem
– epidermal tissue
- ground tissue – parenchyma
- collenchyma
- sclerenchyma
- vascular tissue – xylem and phloem
Organization of leaves – epidermal tissue
- mesophyll
- stomata
Organization of stems - nonwoody
- woody - vascular cambium
- annual ring
Organization of root Plant nutrition - mineral uptake
Transportation of nutrition – xylem: cohesion-tension model
- pholem : pressure-flow model
20.2 Plant Tissues and Cells
• apical meristems
- Plant growth occurs continually from dividing
cells called the meristem.
- located at the tip of root and shoot.
- division of meristem increases the length of
root and shoot
• Three types of specialized plant tissues
- epidermal tissue: form the outer protective
covering of a plant
- ground tissue: fill the interior of a plant
- vascular tissue: transport and supporting
Plant tissues and cells: epidermis (root)
• The outer cell layer of plant tissues is the
epidermis.
• The root epidermis can have epidermal root
hairs to increase surface area for absorbing and
anchoring.
Plant tissues and cells: epidermis (leaves)
• The leaf epidermis is covered with a
waxy cuticle 角質層
- providing a barrier to water loss.
- defend the bacterial disease
• The leaf epidermis also
have stomata which
regulate gas and
water exchange.
plant tissues and cells: Ground Tissue
• The interior of the plant leaves, stems, and roots
is composed of ground tissue(基本組織)
• three cell types in ground tissue.
– Parenchyma (薄壁組織),Collenchyma(厚角組織)
and Sclerenchyma(厚壁組織)
• Parenchyma cells (薄壁組織)
- are the least specialized cell type
- found throughout the plant
- are photosynthetic cells
(with chloroplast).
Plant Tissues and Cells: ground tissue
• Collenchyma cells (厚角組織)
- have thick cell walls.
- are arranged in bundles to
provide flexible support below
the epidermis.
• Sclerenchyma cells (厚壁組織)
- have cell walls reinforced
with lignin.
- often are dead cells.
- provide support in mature
tissues.
Plant tissues and cells: vascular tissue- xylem
•
The xylem (木質部) transports water and minerals
from roots.
- Vessel (導管) elements are one type of xylem with
large, perforated cell walls.
- Tracheids(管胞) are smaller xylem cells whose walls
have numerous pits.
(管胞)
Vascular tissue- phloem
• The phloem (韌皮部) is composed of
- sieve-tube members: have perforated plates
on each end of the cell.
- companion cell(伴細胞): Each sieve-tube
member has a companion cell which has a
nucleus and controls the activity of the enucleated
sieve-tube member.
• sieve-tube member and companion cells are
connected by plamodesmata (胞質間連絲)
Tissues and Cells: vascular tissue- Phloem
plasmodesmata
• vascular cambium(形成層)
- a meristematic vascular tissue
- produces new vascular tissue
Organization of Leaves
• epidermis
- on the top and bottom of a leaf
- often has cuticle, protective hairs or glands.
- Stomata are located on the lower epidermis.
• Mesophyll cells
- photosynthetic cells within the interior of
leaves
– spongy mesophyll: arranged randomly to
increase surface area for gas exchange.
– palisade (防衛) mesophyll (柵狀組織): is
comprised of elongated, vertically-oriented
cells.
Stomata - CO2 in
- water and O2 out
Organization of non-woody stems
herbaceous (草本的) stems
Monocot stems are
randomly distributed
Eudicot stems :
arranged in a ring
Organization of Woody Stems
• Woody stems have three distinct regions.
– Bark (樹皮)
- vascular cambium
– Wood
– Pith (髓)
• vascular cambium(形成層)
- a meristematic vascular tissue
- produces new vascular tissue
• The vascular cambium occurs between the bark and
the wood. The vascular cambium of woody plants
is meristematic and produces new xylem and
phloem cells each year. (called secondary growth)
Woody Stems
Organization of Woody Stems
• Wood is composed of the secondary xylem
produced each year by the stem.
• Spring wood has wide xylem vessels with thin walls,
due to transport of large amounts of water.
• Summer wood: with less water, the xylem vessels
become narrower and with thicker walls.
• Spring and summer
wood together make
an annual ring.
Organization of roots
• Within the root, cells are in different stages of
differentiation.
– zone of cell division: The apical meristem is
composed of dividing cells protected by a root cap.
– zone of elongation: Cells are elongating vertically.
– zone of maturation: contains fully differential cells.
Many of its epidermal cells bear root hairs.
雙子葉
Organization of Roots
• Both eudicot and monocots have the same
growth zones and also have pericycle,
endodermis, cortex, and epidermis.
• The pattern of vascular bundles:
Plant organ – leaves
- stem
- root
- monocot and eudicot
Plant tissue and cell - apical meristem
– epidermal tissue
- ground tissue – parenchyma
•
- collenchyma
- sclerenchyma
- vascular tissue – xylem and phloem
Organization of leaves – epidermal tissue
- mesophyll
- stomata
Organization of stems - nonwoody
- woody - vascular cambium
- annual ring
Organization of root Plant nutrition - mineral uptake
Transportation of nutrition – xylem: cohesion-tension model
- pholem : pressure-flow model
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Plant Nutrition
• Plants are unique in that they require only inorganic
nutrients to survive. Plants convert these inorganic
nutrients to the organic compounds needed for life.
• Some inorganic elements are essential, meaning that
plants have an absolute requirement for those
elements.
•
essential nutrients are divided into two categories
based upon their relative concentrations in plant
tissues.
– Macronutrients are elements that are required in
large amounts.
– Micronutrients are required in small amounts for
specialized functions.
Plant Nutrition
• There are nine macronutrients.
– Carbon, Hydrogen, Oxygen, Phosphorus, Potassium,
Nitrogen, Sulfur, Calcium, Magnesium
• There are seven micronutrients, which serve primarily
as enzyme cofactors.
– Iron, Boron, Manganese, Copper, Zinc, Chloride,
Molybdenum
• Mineral nutrients
- enter plants through the root system
- two mutualistic relationships assist roots in
mineral uptaking
Examples of mutualistic relationship
• In plants legumes(豆), specialized bacteria reside in root
nodules.
- convert nitrogen gas (N2) into nitrate (NO3-) or
ammonium (NH4+)
- The plant roots provide carbohydrates to the bacteria
to support their growth.
• Most plants have a symbiotic relationship with
mycorrhizal fungi (根瘤菌).
- The fungal hyphae increases the surface area
available for water and nutrient uptake.
- The plant roots provide the fungi with carbohydrates
and amino acids.
Transport of Nutrientsin Xylem: water and
mineral
• The cohesion-tension model
- When these stomata are open, water evaporates
from the interior of the leaf to the outside air, a
process called transpiration (蒸散作用)
- As plant leaves transpire water, a tension is
created that pulls water from roots to leaves.
- This tension is maintained because water
molecules display an attraction to one another
called cohesion.
• Adhesion : Water also adheres to the sides of
xylem vessels, so water gives the water column
extra strength and prevents it from slipping back. .
Opening and Closing of Stomata
• The opening and closing of the leaf stomata is
controlled by turgor pressure within the guard cells.
• Stomata open when water enters guard cells and
turgor pressure increases.
• Stomata close when water exits guard cells and
turgor pressure is lost
Transport of organic nutrients in the phloem
• The phloem transport carbohydrates from
photosynthesizing leaves to roots, young leaves,
and other tissues that require carbohydrates.
• The transport of carbohydrates through the phloem
occurs by a mechanism called the pressure-flow
model.
- a source to sink transport.
- As mature leaves photosynthesize, they become
a source of sugar.
- The carbohydrates in the phloem are transported
to tissues that require sugars, called sink tissues
(eg. roots0
Organic Nutrients in the Phloem