Download 植物營養

Chapter 37
Plant Nutrition
植物營養
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A Nutritional Network (營養網路)
• Every organism is an open system connected to its environment
by a continuous exchange of energy and materials.
• In the energy flow and chemical cycling that keep an ecosystem
alive, plants and other photosynthetic autotrophs perform the
key step of transforming inorganic compounds into organic ones.
• Plants need sunlight as the energy source for photosynthesis.
And to synthesize organic matter, plants also require raw
materials in the form of inorganic substances: carbon dioxide,
water, and a variety of minerals present as inorganic ions in the
soil.
• With its ramifying root system and shoot system, a plant is
extensively networked with its environment----the soil and air,
which are the reservoirs of the plants inorganic nutrients.
• For a typical plant water and minerals come from the soil, while
carbon dioxide (CO2) comes from the air
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Key Concepts
• Concept 37.1: Plants require certain chemical
elements to complete their life cycle
• Concept 37.2: Soil quality is a major
determinant of plant distribution and growth
• Concept 37.3: Nitrogen (N) is often the mineral
that has the greatest effect on plant growth
• Concept 37.4: Plant nutritional adaptations (營
養適應) often involve relationships with other
organisms
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• The branching root system and shoot system
of a vascular plant
– Ensure extensive networking with both
reservoirs of inorganic nutrients (無機營養)
Root and shoot systems
of a pea seedling
Figure 37.1
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• Concept 37.1: Plants require certain chemical elements to
complete their life cycle
• Plants derive most of their organic mass from the CO2 of
air, but they also depend on soil nutrients such as water
and minerals
• Mineral nutrients
CO2, the source of carbon
for photosynthesis, diffuses
into leaves from the air
through stomata.
CO2
Minerals
Roots absorb H2O and
minerals from the soil.
H2
O
O2
Through stomata, leaves
expel H2O and O2.
O2
CO2
H2O
Roots take in O2 and expel CO2.
The plant uses O2 for cellular
respiration but is a net O2 producer.
Figure 37.2
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Functions of water in plants
• Solvent in the cell
• Photosynthetic reactant
• Metabolic reactant or product
• Respiration
• Vacuolar content for cell elongation and
extension
• Turgor pressure
• Others
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Macronutrients and Micronutrients
巨量營養素與微量營養素
• More than 50 chemical elements
– Have been identified among the inorganic
substances in plants, but not all of these are
essential (必需的/必要的)
• Essential elements (必需元素)
– A chemical element is considered essential If it
is required for a plant to complete a life cycle
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Hydroponic culture and essential elements(水耕
法與必需元素)
• Researchers use hydroponic culture (水耕法) to
determine which chemicals elements are essential
APPLICATION In hydroponic culture, plants are grown in mineral solutions without soil.
One use of hydroponic culture is to identify essential elements in plants.
TECHNIQUE Plant roots are bathed in aerated solutions of known mineral composition.
Aerating the water provides the roots with oxygen for cellular respiration. A particular mineral,
such as potassium, can be omitted to test whether it is essential.
Control: Solution
containing all minerals
Experimental: Solution
without potassium (K+)
RESULTS If the omitted mineral is essential, mineral deficiency symptoms occur, such as
stunted growth and discolored leaves. Deficiencies of different elements may have different
symptoms, which can aid in diagnosing mineral deficiencies in soil.
Figure 37.3
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17 essential elements=9 macro- and 8 micrnutrients
• Nine of the essential elements are called
macronutrients (巨量營養素), because plants
require them in relatively large amounts
– C, O, H, N, S, P, K, Ca
• The remaining eight essential elements are
known as micronutrients (微量營養素)
– Because plants need them in very small
amounts
– Cl, Fe, B, Mn, Zn, Cu, Mo, Ni
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• Essential elements in plants


Table 37.1
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Symptoms of Mineral Deficiency (礦物質缺乏的症狀)
• The symptoms of mineral deficiency
– Depend partly on the nutrient’s function
– Depend on the mobility of a nutrient within the plant
– Chlorosis (黃化現象)
• Deficiency of a mobile nutrient (移動力強的元素)
– Mg
– Usually affects older organs more than young ones
– Drawing power (汲取力) is stronger in young organs
• Deficiency of a less mobile nutrient (移動力弱的元素)
– Fe
– Usually affects younger organs more than older
ones
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• The most common deficiencies
– Are those of nitrogen (N), potassium (K), and
phosphorus (P)
Healthy/normal
磷缺乏 Phosphate-deficient
鉀缺乏 Potassium-deficient
氮缺乏 Nitrogen-deficient
Figure 37.4
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• Concept 37.2: Soil quality (土壤質地) is a major
determinant of plant distribution and growth
• Along with climate (氣候)
– The major factors determining whether particular
plants can grow well in a certain location are the
texture and composition of the soil (土壤質地與組成)
• Texture (質地)
– Is the soil’s general structure
• Composition (組成)
– Refers to the soil’s organic and inorganic chemical
components
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Texture and Composition of Soils(土壤質地與組成)
• Various sizes of particles derived from the
breakdown of rock (岩石) are found in soil
– Along with organic material (humus腐植質) in
various stages of decomposition (分解)
• The eventual result of this activity is topsoil (頂
層土壤)
– A mixture of particles of rock and organic
material
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• The topsoil (表土/頂層土壤) and other distinct soil
layers or horizons (土壤分層)
– Are often visible in vertical profile (垂直剖面/斷面)
where there is a road cut or deep hole
A
The A horizon is the topsoil, a mixture of
broken-down rock of various textures, living
organisms, and decaying organic matter.
B
C
The B horizon contains much less organic
matter than the A horizon and is less
weathered (風化程度).
The C horizon, composed mainly of
partially broken-down rock, serves as the
“parent” material for the upper layers of
soil.
Figure 37.5. Soil layers or horizons (土壤分層)
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The availability (可利用性) of soil water and minerals
• After a heavy rainfall, water drains away from the larger
spaces of soil. But smaller spaces retain water because
of its attraction to surfaces of clay and other particles
• The film of loosely bound water is usually available to
plants (與土壤結合不緊密的薄水層的水才能被根吸收)
親水性
Soil particle surrounded
土壤粒子
by film of water
(a) Soil water. A plant cannot
extract all the water in the soil
because some of it is tightly held
by hydrophilic soil particles.
Water bound less tightly to soil
particles can be absorbed by the
root.
土壤結合不緊密
親水性土壤粒子
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Root hair
Water available
to plant 土壤結合
不緊密
Air space
Figure 37.6a
Cation exchange in oil (土壤中的陽離子交換)
• Acids (???) derived from roots contribute to a
plant’s uptake of minerals when H+ displaces (排擠
/取代) mineral cations from clay particles (粘土粒
子)
土壤粒子表面帶負電
Soil particle
K –
+
–– –
Cu2+ K+
– –
Mg2+
– K
+
–
–
Ca2+
H+
H2O + CO2
2
H2CO3
HCO3–
Root hair
+ H+
1
(b) Cation exchange in soil. Hydrogen ions
(H+) help make nutrients available by
displacing positively charged minerals
(cations such as Ca2+) that were bound
tightly to the surface of negatively charged
soil particles. Plants contribute H+ by (1)
secreting it from root hairs and also by (2)
cellular respiration, which releases CO2 into
the soil solution, where it reacts with H2O to
form carbonic acid (H2CO3). Dissociation of
this acid adds H+ to the soil solution.
Figure 37.6b
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Soil Conservation and Sustainable Agriculture
土壤保育與永續(可持續)農業
• In contrast to natural ecosystems (自然生態系
統)
– Agriculture (1) depletes the mineral content of
the soil, (2) taxes water reserves, and (3)
encourages erosion
• The goal of soil conservation strategies (土壤保
育策略的目標)
– Is to minimize this damage
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Fertilizers (肥料)
• Commercially produced fertilizers
– Contain minerals that are either mined or
prepared by industrial processes
• “Organic” fertilizers (有機肥料)
– Are composed of manure (糞便), fishmeal (魚
肉), or compost (堆肥)
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Deficiency warnings from “smart” plants
• Agricultural researchers are developing ways to
maintain crop yields while reducing fertilizer use
• Genetically engineered “smart” plants (遺傳工程智
慧植物) inform the grower when a nutrient
deficiency is imminent (急迫性營養缺失)
No phosphorus
deficiency
Figure 37.7
Beginning
phosphorus
deficiency
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Well-developed
phosphorus
deficiency
Irrigation (灌溉)
• Irrigation, which is a huge drain on water
resources when used for farming in arid
regions (乾旱地區)
– Can change the chemical makeup of soil
• Topsoil from thousands of acres of farmland
– Is lost to water and wind erosion (水與風的侵
蝕) each year in the United States
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等高線耕地
• Certain precautions (預警)
– Can prevent the loss of topsoil
Figure 37.8
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• The goal of soil management (土壤管理的目標)
– Is sustainable agriculture (永續農業), a
commitment embracing (using) a variety of
farming methods that are conservation-minded
(保育理念)
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Soil Reclamation (土壤復育)
• Some areas are unfit for agriculture
– Because of contamination of soil or
groundwater with toxic pollutants
• A new method known as phytoremediation (植
物復育)
– Is a biological, nondestructive (非破壞性)
technology that seeks to reclaim contaminated
areas
– A part of bioremediation (生物復育)
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•Concept 37.3: Nitrogen is often the mineral that has the
greatest effect on plant growth
•Plants require nitrogen (N) as a component of
– Proteins
– nucleic acids
– chlorophyll
– other organic molecules
G
A
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C
T
U
Soil Bacteria and Nitrogen Availability (氮的利用)
• Nitrogen-fixing bacteria (固氮細菌) convert atmospheric N2
to nitrogenous minerals that plants can absorb as a
nitrogen source for organic synthesis
• N2+8e-+8H++16ATP
Atmosphere
nitrogenase
Atmosphere
N2
1.固氮細菌
N2
2NH3+H2+16ADP+16Pi
Soil
N2
4.脫氮細菌
Nitrogen-fixing
bacteria
Denitrifying
bacteria
H+
Soil
(From soil)
銨鹽
NH
氨
3
離子
(ammonia)
+
NH4
(ammonium) Nitrifying
bacteria
Organic material (humus)
有機物質(腐質土)
Ammonifying
bacteria
2.氨化細菌
3.硝化細菌
Nitrate and
nitrogenous
organic
compounds
exported in
xylem to
shoot system
NH4+
NO3–
(nitrate)
硝酸鹽
離子
Root
Figure 37.9. The role of soil bacteria in the nitrogen nutrition of plants.
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Improving the Protein Yield of Crops
• Agriculture research in plant breeding
– Has resulted in new varieties of maize, wheat,
and rice that are enriched in protein
• Such research
– Addresses the most widespread form of
human malnutrition (營養不良): protein
deficiency
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• Concept 37.4: Plant nutritional adaptations
often involve relationships with other organisms
植物營養適應通常包括其與其它微生物的關係
• Two types of relationships plants have with
other organisms are mutualistic (相互的)
– Symbiotic nitrogen fixation (共生的固氮作用)
– Mycorrhizae (菌根)
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The Role of Bacteria in Symbiotic Nitrogen
Fixation (共生固氮作用細菌的角色)
• Symbiotic relationships with nitrogen-fixing
bacteria (固氮細菌) by coevolution (共同演化)
– Provide some plant species with a built-in
source of fixed nitrogen
• From an agricultural standpoint
– The most important and efficient symbioses (共
生) between plants and nitrogen-fixing bacteria
occur in the legume family (peas, beans, and
other similar plants)
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• Along a legumes possessive roots are swellings
(膨脹物/隆起物) called nodules (根瘤), plant cells
– Composed of plant cells that have been “infected”
by nitrogen-fixing Rhizobium bacteria
Nodules 根瘤
Roots
(a) Pea plant root. The bumps (腫塊) on this pea plant root are nodules containing
Rhizobium bacteria. The bacteria fix nitrogen and obtain photosynthetic products supplied
by the plant.
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Figure 37.10a
• Inside the nodule (根瘤), which a plant cell
– Rhizobium bacteria assume a form called bacteroids
(類菌體), which are contained within vesicles (囊泡)
5 m
formed by the root cell
Infected root
cell of nodule
Bacteroids
within vesicle
囊泡中的
類菌體
vesicle
Uninfected cell of root
大豆根瘤中的類菌體
(b) Bacteroids in a soybean root nodule. In this TEM, a cell from a root nodule of soybean
is filled with bacteroids in vesicles. The cells on the left are uninfected.
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Figure 37.10b
• The bacteria of a nodule (根瘤中的細菌)
– Obtain sugar from the plant and supply the
plant with fixed nitrogen
• Each legume (豆科)
– Is associated with a particular strain (菌株) of
Rhizobium
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Development of a soybean root nodule
(大豆根瘤的發育)
(1) Roots emit chemical
signals that attract
Rhizobium bacteria. The
bacteria then emit
signals that stimulate
root hairs to elongate
and to form an infection
thread by an
invagination of the
plasma membrane.
根瘤菌
Rhizobium
bacteria
Infection
thread
感染絲
類菌體
Bacteroid
Infected
root hair
(2) The bacteria penetrate the
cortex within the Infection
thread. Cells of the cortex
and pericycle begin dividing,
Dividing cells and vesicles containing the
in pericycle
bacteria bud into cortical
2.
cells from the branching
infection thread. This
process results in the
formation of bacteroids
Dividing cells
in root cortex
1
2
Developing
root nodule
3
(4) The nodule develops
4
vascular
tissue that
supplies nutrients to the
nodule and carries
nitrogenous compounds
into the vascular
cylinder for distribution
throughout the plant.
Figure 37.11
發育中
的根瘤
Bacteroid
類菌體
4
類菌體
Bacteroid
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Nodule
vascular
tissue
根瘤的
維管組織
(3) Growth
continues in
3
the affected regions of
the cortex and pericycle,
and these two masses of
dividing cells fuse (融合),
forming the nodule.
The Molecular Biology of Root Nodule Formation
• The development of a nitrogen-fixing root nodule depends
on chemical dialogue (化學對話) between Rhizobium
bacteria and root cells of their specific plant hosts
Activation of
Nod box by
activated Nod D
Expression
of Nod gene
Synthesis of
Nod factor
Activation of
factor Nod D
by flavonoid
Chemical Signal
between root
and Rhizobium
Flavonoid released
by root as signal
Nod factor trigger development by
the root of the infection thread and
nodule
Activation of early nodule genes, leading to formation
of infection thread and proliferation of cortical cells
此圖見第六版
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Symbiotic Nitrogen Fixation and Agriculture
共生的固氮作用與農業
• The agriculture benefits of symbiotic nitrogen
fixation
– Underlie crop rotation (作物輪作/輪耕)
• In this practice
– A non-legume such as maize is planted one
year, and the following year a legume is
planted to restore the concentration of nitrogen
in the soil (恢復土壤氮濃度)
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Mycorrhizae and Plant Nutrition (菌根與植物營養)
• Mycorrhizae (菌根), may be an evolutionary adaptation
– Are modified roots (變形根) consisting of mutualistic
(相互的) associations of fungi and roots
• The fungus (真菌)
– Benefits from a steady supply of sugar donated by the
host plant (寄主植物穩定地供給糖類給真菌)
• In return, the fungus
– Increases the surface area of water uptake and
mineral absorption and supplies water and minerals to
the host plant (真菌回報以增加寄主植物根的表面績，
以增加水份與礦物質的吸收)
– Produce growth factor and antibiotics for host plants
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The Two Main Types of Mycorrhizae (菌根)
• In ectomycorrhizae (外根菌), no formation of root hair
– The mycelium (菌絲體) of the fungus forms a dense
sheath (濃密的鞘) over the surface of the root
表皮
皮層
Epidermis
Cortex
Mantle
(fungal
sheath)
外套膜
100 m
Endodermis
內皮
a
Mantle
(fungal
sheath)
外套膜
Fungal
hyphae
between
cortical
cells
(colorized SEM)
(a) Ectomycorrhizae. The mantle of the fungal mycelium ensheathes the root. Fungal
hyphae extend from the mantle into the soil, absorbing water and minerals, especially
phosphate. Hyphae also extend into the extracellular spaces of the root cortex,
providing extensive surface area for nutrient exchange between the fungus and its host
plant.
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Figure 37.12a
The Two Main Types of Mycorrhizae (菌根)
• In endomycorrhizae (內根菌), formation of root hair
– Microscopic fungal hyphae extend into the root
表皮
Epidermis
皮層
Cortex
Cortical cells
10 m
內皮
2
Fungal hyphae
菌絲
Root hair
Endodermis
Vesicle
Casparian
strip
Arbuscules
枝狀瘤
(LM, stained specimen)
(b) Endomycorrhizae. No mantle forms around the root, but microscopic fungal
hyphae extend into the root. Within the root cortex, the fungus makes extensive
contact with the plant through branching of hyphae that form arbuscules, providing
an enormous surface area for nutrient swapping. The hyphae penetrate the cell walls,
but not the plasma membranes, of cells within the cortex.
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Figure 37.12b
Agricultural Importance of Mycorrhizae
(菌根在農業上的重要性)
• Farmers and foresters
– Often inoculate (接種) seeds with spores of
mycorrhizal fungi to promote the formation of
mycorrhizae
• Green manure and crop rotation (綠肥與輪作)
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Epiphytes, Parasitic Plants, and Carnivorous Plants
• Some plants have nutritional adaptations (營養適
應) that use other organisms in nonmutualistic
ways (非互利共生)
– Epiphytes (附生植物)
– Parasitic Plants (寄生植物)
– Carnivorous Plants (食蟲植物)
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Exploring unusual nutritional adaptations in plants
EPIPHYTES
Staghorn fern,
an epiphyte
PARASITIC PLANTS
Host’s
phloem
Dodder
Haustoria
Mistletoe,
a photosynthetic
parasite
Dodder, a
nonphotosynthetic
parasite (菟絲子)
Indian pipe, a
Nonphotosynthetic
parasite (水晶蘭)
CARNIVOROUS PLANTS
Venus’ flytrap
Pitcher plants
Figure 37.13
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Molecular Biology of Root Nodule Formation
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