Plant Physiology
1)
2)
3)
水的功能與運輸
光合作用
植物賀爾蒙
國立高雄大學生科系 葛孟杰 副教授
火星有液態水 NASA找到鐵證
2015-09-29 03:39:35 聯合報 編譯陳韋廷／綜合報導
美國太空總署（ＮＡＳＡ）二十八日召開記者會宣布，證據顯示火星上有定期出現的液態水。
研究報告中說，相關跡象「強力支持」今日火星上有水的假設。天文物理學家早已認為，這些會隨
著季節變化定期出現的紋理，可能是鹽水在火星地表流動造成。
這些可能是鹽水造成的暗色線條，長度達數百公尺，寬度通常不超過五公尺，在溫暖季節會出現在
火星地表坡面，慢慢延長，然後在地表溫度變冷後逐漸消逝。
今年四月，科學家也曾發表研究指出，「過氯酸鹽」在火星上廣泛分布。這種物質會降低水的冰點，
讓火星上的鹽水在較冷的氣溫下仍保持液態能夠流動。
照片中深色的長條區，研究人員推斷是水流從山頂往下流的路線，經過分析，成分是需要
水才能形成的物質。科學家不能確定水是從哪裡來的，可能來自於地底下的冰，或者是鹹
的地下水上升，或者是凝結的火星薄大氣。 NASA火星探測計畫首席科學家Michael Meyer
認為：「因為這個發現，我們懷疑今天的火星也許存在有適合居住的環境。」 - See more
at: http://www.cw.com.tw/article/article.action?id=5071180#sthash.8pA1SFom.dpuf
Water in plant life
1. Cell walls allow plant cells to build up large internal
hydrostatic pressures, called turgor pressure. (膨壓)
2. Turgor pressure is essential for many physiology processes,
including cell enlargement, stomatal opening, transport in
the phloem, and various transport processes across
membranes. (膨壓很好用)
3. Turgor pressure also contribute to the rigidity and
mechanical stability of nonlignified plant tissue. (打人會痛)
Water is frequently a limiting resource for plants
1. Most (~97%) of the water absorbed by a plant’s roots is carried
through the plant and evaporates from leaf surfaces. Such water loss
is called transpiration. (蒸散作用)
2. In contrast, only a small amount of the water absorbed by roots
actually remains in the plant to supply growth (~2%) or to be
consumed in the biochemical reactions of photosynthesis and other
•年降雨量
metabolic process (~1%). (賺來的水大部分都留不住)
3. The uptake of CO2 is coupled to the loss of water through a
common diffusion pathway. (有賺就有賠)
6
The structure and properties of water
7
1.
Water is a polar molecule that forms hydrogen bonds (不是口香糖喔)
2.
Water is an excellent solvent (溶劑)
3.
Water has distinctive thermal properties relative to its size (比熱)
4.
Water molecules are highly cohesive (很粘)
5.
Water has a high tensile strength (魯夫~)
Hydrogen Bonds
1. A hydrogen bond is an interaction between a covalently bonded hydrogen atom on a donor atom and a pair of nonbonded
electrons on an acceptor atom.
2. The atom to which hydrogen is covalently bonded is called the hydrogen-bond donor, and the atom with the nonbonded
electron pair is called the hydrogen-bond acceptor. The interaction between the donor and acceptor is typically represented by a
dotted line between the acceptor atom and the shared H.
3. The more electronegative the donor atom, the more negative charge it withdraws from the hydrogen to which it is bonded; thus,
the hydrogen becomes more positive and is more strongly attracted to the electron pair of the acceptor.
4. Among the atoms encountered in biological compounds, only O and N
have appropriate electronegativities to serve as strong donors.
The Role of Water in Biological Processes
► Water allows molecules be able to move about, encounter one another, and change partners frequently in the
complicated processes of metabolism and synthesis.
A: The Structure and Properties of Water
1. The electron arrangement of a single water that the six electrons in the outer orbitals of the oxygen atom, two
are involved in covalent bonds to the hydrogens. The other four electrons exist in nonbonded pairs, which are
excellent hydrogen-bond acceptors.
2. The OH groups in water are strong hydrogen-bond donors. Thus each water molecule is both a hydrogen-bond
donor and a hydrogen-bond acceptor, capable of forming up to four hydrogen bonds simultaneously.
3. The strength of this extensive H-bond network gives water an unusually large heat capacity, and the
vaporization of water requires a large amount of energy for a molecule of its size. Both the heat of vaporization
and the boiling point of water are therefore unusually high, and water remains in the liquid state at
temperatures characteristic of much of the earth’s surface.
4. Ice is a molecular lattice formed by indefinite repetition of a tetrahedral hydrogen-bonding pattern. Each
molecule acts as a hydrogen-bond donor to two others and as an acceptor from two others. Because of the
length of the hydrogen bonds, the structure is a relatively open one, which accounts for the low density of ice.
Water is an excellent solvent
It is the hydrogen bonding ability of water and its polar structure that make it a particularly good
1.
solvent for ionic substances and for molecules such as sugars and proteins that contain polar –
OH or –NH2 groups. (有了氫鍵就容易跟糖還有蛋白質混得很熟)
11
Water has distinctive thermal properties
1.
The extensive hydrogen bounding between water molecules results in water having both a high
specific heat capacity and a high latent heat of vaporization (蒸發的潛熱). (口香糖讓水可以
比較穩定)
2.
Specific heat capacity is the heat energy required to raise the temperature of a substance by a set
amount. (比熱)
3.
Latent heat of vaporization is the energy needed to separated molecules from the liquid phase
and move them into the gas phase-a process that occurs during transpiration. (蒸散)
Water molecules are highly cohesive
1.
(內聚力)
The energy required to increase the surface area
of a gas-liquid interface is know as surface
tension. (J m-2 or N m-1). (空氣跟水)
2.
The extensive hydrogen bonding in water also
gives rise to the property known as cohesion, the
mutual attraction between molecules. (分子間抱
在一起的力量)
Adhesion
(附著力)
1.
A related property, called adhesion, is the
attraction of water to solid phase. (水跟物體
抱在一起的力量)
2.
The contact angle describes the shape of the
air-water interface and thus the effect that the
surface tension has on the pressure in the
liquid.
3.
Wettable surfaces (hydrophilic substrate) have
contact angle of less than 900.
Capillarity
1.
Cohesion, adhesion, and surface
tension give rise to a phenomenon
known as capillarity (分子間抱在一起
的力量+分子跟物體抱再一起的力量+
表面張力=毛細作用).
2.
At equilibrium, the water level within the
capillary tube will be higher than that of
the water supply at its base.
3.
Hg on the clean glass has a contact angle
of approximately 1400.
胎壓
家用馬達
水壓
Water potential
•
(水勢)
Water potential was defined as the chemical potential of water divided by partial molar of water.
(ΨW= Ψ s+ Ψ p+ Ψ g)

Chemical potential is a quantitative expression of the free energy associated with a substance.

Three major factors contribute to cell water potential

Concentration (Ψ s): solute potential or osmotic potential

Pressure (Ψ p): hydrostatic pressure of the solution. (靜水壓, 液體無流動時的壓力)

gravity (Ψ g): The height of the water above the reference-state water.
–
–
–
Solute potential: Ψ s=-RTcs
Hydrostatic pressure: Ψ p
Gravity pressure: Ψ g=ρWgh
Water potential of plant cells
1.
Plant cell typically have negative water potentials. (植物是月光族)
2.
Water enters or leaves a cell according to the water potential gradient.
(水要走還是要留~全看Ψw說話)
3.
In leave of well-watered plants, Ψw ranges from -0.2 to about -1.0 Mpa
in herbaceous plants and to -2.5 Mpa in trees and shrubs. (木本植物欠
的比較多)
4.
Leaves of plants in arid climates can have much lower Ψw, down to
below -10 Mpa under the most extreme conditions. (遇到惡劣的環境
當然要欠更多)
The concept of water potental
•A flaccid cell is dropped in 0.1 M
sucrose
1. When a flaccid cell is placed in a solution that has a water potential greater
餓扁扁的細胞
(less negative) than the cell’s water potential, water will move from the
solution into the cell (from high to low water potential). (細胞欠比較大~水
往裡面流)
2. As water enter, the cell wall resists being stretched, increasing the turgor
pressure of the cell. (水流進去之後~細胞表示壓力很大)
胖胖的細胞
3. At equilibrium, the cell Ψp has increased sufficiently to raise the cell Ψw
to the same value as the Ψw of the solution, and net water movement ceases.
(平衡之後~細胞內外的Ψw要一樣)
•Cross section of a cactus stem
1.
The stem of Cactus (仙人掌) consist of an outer,
photosynthetic layer that surrounds non-photosynthesis
tissues that serve as a water storage reservoir. (外面賺錢裡
面存水)
2.
The water storage cells are large and have thinner walls than
the photosynthetic cells, and are thus more flexible. (存水的
細胞ㄉㄨㄞ ㄉㄨㄞ 的)
3.
The solute concentration of the water storage cells decreases
during drought, in part due to the polymerization of soluble
sugars into insoluble starch granules. (乾旱失水時就在家
裡堆積不能吃的糖果~讓Ψs上升)
Aquaporins facilitate the movement of water across cell membranes
1.
Aquaporins are integral membrane proteins that form
water-selective channels across the membrane. (給水走
的捷徑)
2.
Although Aquaporins may alter the rate of water
movement across the membrane, they do not change the
direction of transport or the driving force for water
movement. (不能改變方向)
3.
Aquaporin can be reversibly “gated: in response to
physiological parameters such as intercellular pH and
Ca2+ levels. (蓋子可以開關)
Plant water status
1.
Physiological changes due to dehydration (脫水)
In many plants reduction in water supply inhibit shoot growth and leaf expansion
but stimulate root elongation. (缺水時只有根會很高興)
2.
Solute accumulation help cells maintain turgor and volume
Plants that grow in saline environments called halophytes. (缺水時會在家裡亂堆
東西)
Physiological changes due to dehydration
Root haris make intimate contact with soil particles
Water moves through the soil
by bulk flow
1. The rate of water flow in soils depends on two factors: the size of the pressure
gradient through soil and the hydraulic conductivity of the soil. (土的壓力跟水的
流動性)
2. Soil hydraulic conductivity: A measure of the ease with which water move through
the soil. (水在土裡的靈活度)
3. Permanent wilting point: Plants cannot regain turgor pressure even if all water loss
through transpiration ceases. (再也喚不回的分手~)
4. 犀利人妻~回不去了
Water absorption by root hairs
1. Root hairs are filamentous outgrowths of root epidermal cells that greatly increase
the surface area of root, thus providing greater capacity for absorption of ions and
water from the soil. (根毛是長在表皮細胞外用來增加離子跟水分吸收表面積的)
2.
Water enters the root most readily near the root tip. (吸水多半靠根尖)
27
Water moves in the root
1.
Water moves in the root via (a) Apoplast pathway, (b) symplast pathway and (c) Transmembrane pathway. (三條路可
以走)
2.
Casparian strip: It is a band of radial cell walls in the endodermis that is impregnated with the waxlike, hydrophobic
substance suberin. (卡氏帶設路障攔路收錢)
3.
The casparian strip breaks the continuity of the apoplast pathway, forcing water and solutes to pass through the
plasma membrane in order to cross the endodermis. (卡氏帶可以打斷細胞間隙的運送!逼水面對細胞膜的考驗)
Casparian strips.
An Arabidopsis root stained for PI (red)
to mark cell membranes, and CASP1-GFP
(green) to show the Casparian strip
membrane domain. (Photo: Julien
Alassimone, University of Lausanne.)
30
Water moves in the root
1.
The permeability of roots to water depends strongly on the presence of aquaporins.
(開小門)
2. The permeability of aquaporins can be regulated in response to intracellular pH.
(管小門的怕酸民)
3. Decreased rates of respiration, in response to low temperature or anaerobic
conditions, can lead to increases in intracellular pH.
(鄉民酸人是有原因的-低溫缺氧)
Aquaporin (開門的藝術)
1. The permeability of aquaporins can be regulated in
response to intracellular pH.
2. Decreased rates of respiration can lead to increases
in intracellular pH. This increase in cytoplasmic
pH alters the conductance of aquaporins. (呼吸變慢
pH上昇~門開關受影響)
3. Closure in response to drought results from the
dephosphorylation of two highly conserved serine
residues. (乾燥~去P~關門)
4. Closure during flooding resulting from the
protonation of a conserved histidine. (淹水!質子化
~關門)
Solute accumulation in xylem can generate “root pressure”
1.
Root pressure is most likely to occur when soil water potentials are high
and transpiration rate are low. (根壓)
2.
Plants that develop root pressure frequently produce liquid droplets on the
edges of their leaves, a phenomenon known as guttation. (泌溢現象；植
物流口水)
3.
Positive xylem pressure causes exudation of xylem sap through
specialized pores called hydathodes (葉尖水孔) that are associated with
vein endings at the leaf margin.
4.
Guttation is most noticeable when transpiration is suppressed and the
relative humidity is high, such as during night. (早晚容易流口水)
Water transport through the xylem
1.
The xylem consist of two types of tracheary elements Vessel element and
Tracheid. (水分運送系統有兩種)
2.
Water moves through the xylem by pressure-driven bulk flow. It is
responsible for long-distance transport of water in the xylem. (遠距離
運送-靠壓力)
3.
Water movement through the xylem requires a smaller pressure gradient
than movement through living cells. The maturation of xylem is resulted
from Programmed cell death (Pcd). (自殺是xylem產生的方法)
4.
The cohesion-tension theory explains water transport in the xylem. (免
錢的最好用)
5.
Xylem transport of water in the tree faces physical challenges. (水分運
送在木本很辛苦)
6.
Plants minimize the consequences of xylem cavitation. (氣栓問題必須
面對)
Tracheary elements
1. Vessel elements are found in angiosperm, a small
group of gymnosperm called the Gnetales (麻藤科),
and some ferns.
2. Tracheid are present in both angiosperms and
gymnosperm, as well as in ferns and other groups of
vascular plants
1.
Tracheids are elongated, spindle-shape
cells that are arranged in overlapping
vertical files.
2. Pits of one tracheid are typically located
opposite pits of an adjoining tracheid, form
pit pairs. (頭殼有洞沒藥醫~Tracheid 有洞
沒氣栓)
1.
Vessel elements: it tend to be shorter and wider than tracheids and have perforated end walls that
form a perforation plate at each end of their later walls. (貫通的平板)
2.
The perforated end walls allow vessel elements to be stacked end to end to form a much longer
conduit called a vessel.
3. (50 to 400 m in diameter and length )
Cavitation
1. Cavitation blocks water movement because of
the formation of gas-filled conduits. (氣栓)
2. Water can detour around the blocked vessel by
moving through adjacent tracheary elements.
(繞路)
3. The very small pores in the pit membranes
help prevent embolisms from spreading between
xylem conduits. (防止擴散)
Vessel elements
Tracheids
The cohesion-tension theory explains water transport
in the xylem
1.
The pressure gradients needed to move water through the xylem could result from the generation of positive
pressures at the base of the plant or negative pressures at the top of the plant. (下面正壓~上面負壓)
2.
The negative pressure that causes water to move up through the xylem develops at the surface of the cell walls in
the leaf. (上面負壓來自葉子表面)
3.
Because water adheres to the cellulose microfibrils and other hydrophilic components of the cell wall, as water
evaporate from cells within the leaf, the surface of the remaining water is drawn into the interstices of the cell wall.
Because of the high surface tension of water, the curvature of these interfaces induces a tension or negative
pressure in the water.
4.
The cohesion-tension theory explains how the substantial movement of water through plant can occur without the
direct expenditure of metabolic energy. (Water坐免錢的霸王車)
Gas bubbles in the Xylem
1. The most important nucleation sites are gas bubbles. (泡泡)
2. The pit membranes serve as filters, preventing gas bubbles from entering the xylem. (Pit
攔下泡泡)
3. However, when exposed to air on one side-due to injury, leaf abscission, or the
existence of a neighboring gas-filled conduit-pit membranes can serve as sites of entry
for air. This phenomenon is called air seeding. (空氣從斷口處，或很多氣泡的細胞進去)
4. A second mode by which bubbles can form in xylem conduits is freezing of the xylem
tissue. (太冷也會有很多氣泡)
5. The phenomenon of bubble expansion is known as cavitation and the resulting gas-filled
void is referred to as an embolism. (栓塞)
Plants minimize the consequence of xylem cavitation
1.
Gas bubble cannot easily pass through the small pores of the pit membranes.
(孔小不會擴散)
2. Gas bubbles can also be eliminated from the xylem (融掉)
1. At night, when transpiration is low, water vapor and gases may simply
dissolve back into the solution of the xylem. (晚上乖乖睡覺消除脹氣)
2.
Some plant develop positive pressures (Root pressures) in the xylem, such
pressures shrink bubbles and cause the gases to dissolve. (在根堆東西有助
消化脹氣)
Water Movement from the leaf to the Atmosphere
1.
Leaves have a large hydraulic resistance (離開葉子不容易)
2.
The driving force for transpiration is the difference in water vapor concentration. (水氣濃
度影響蒸散作用)
3.
Water loss is regulated by the pathway resistances. (阻礙的力量)
4.
Stomatal control couples leaf transpiration to leaf photosynthesis. (氣孔同時控制了兩種
反應)
Water Movement from the leaf to the
Atmosphere
The transpiration rate
1.
The effectiveness of plants in moderating water loss while
allowing sufficient CO2 uptake for photosynthesis can be
assessed by a parameter called the transpiration ratio.
2.
The (C3) 3-carbon compound (H2O: CO2 =400:1).
3.
The (C4) 4-carbon compound (H2O: CO2 =150:1).
4.
The (CAM) Crassulacean acid metabolism (H2O: CO2
=50:1).
Pathway resistance
1.
The thickness of the boundary layer is determines primarily by wind speed and leaf size. When wind velocity is high, the
moving air reduces the thickness of the boundary layer at the leaf surface, reducing the resistance of this layer.
2.
Various anatomical and morphological aspects of the leaf can influence the thickness of the boundary layer. (Hair on the
surface, Sunken stomata, the size and shape of leaves and leaf orientation). Some species are able to change the
orientation of their leaves and thereby influence their transpiration rates.
3.
Many grass leaves roll up as they experience water deficit. Even wilting can help ameliorate high transpiration rates by
reducing the amount of radiation intercepted resulting in lower leaf temperature and a decrease in △ CWV.
Guard cells
1.
A pair of specialized epidermal cells, which surround the stomatal pore.
2.
Guard cell are found in leaves of all vascular plants, and they are also present in more
primitive plants, such as hornworts (金魚藻) and mosses (蘚苔).
3.
Guard cells show considerable morphological diversity.
1.
Dumbbell shape: It has subsidiary cells, present in grasses and a few other
monocots.
2.
Kidney shape: It has no subsidiary cells, present in all dicots, gymnosperms, and
many monocots.
A stoma from grass
1. The bulbous ends of each guard
cell show their cytosolic content
and joined by the heavily
thickened walls
2. 2560 X
3. Dumbbell shape
1.
Scanning electron
micrographs of onion
epidermis
2.
(1640X)
3.
Kidney shape
An increase in guard cell turgor pressure opens the
stoma
1.
Environmental factors such as light intensity and quality, temperature, leaf water status,
and intracellular CO2 concentrations are sensed by guard cells and these signals are integrated
into well-defined stomatal responses.
2.
The early aspects of this process are ion uptake and other metabolic changes in the guard cells.
3.
Subsidiary cells appear to play an important role in allowing stomata to open quickly and to
achieve large apertures. (幫忙拉開)
4.
A rapid transfer of solutes out of subsidiary cells and into the guard cells cause the former to
decrease in both turgor pressure and size, facilitating the expansion of guard cells in the
direction away from the stomatal pore. (備胎~灌食)
2) 光合作用
Photosynthesis: Carbon reactions
— dark reaction → carbon reactions of photosynthesis
— take place in stroma
Plants that survive solely on C3 fixation (C3 plants) tend to thrive in areas where sunlight
intensity is moderate, temperatures are moderate, carbon dioxide concentrations are around
200 ppm or higher and groundwater is plentiful.
The C4 carbon cycle
Crassulacean acid metabolism (CAM)
Cacti, pineapple, vanilla, and agave.
Stomatal control couples
leaf transpiration to leaf photosynthesis
* Compromise: water loss and carbon dioxide uptake
CO2 gradient  water vapor gradient
* Transpiration ratio: the amount of water transpired divided
by the amount of carbon dioxide uptake.
 Water use efficiency
*
Transpiration ratio Water use efficiency
C3
500
0.002
C4
250
0.004
CAM
50
0.02
* CO2 : concentration gradient low, diffusion rate slow, and
more resistance for assimilation.
3) 植物賀爾蒙
57
Plant Hormone
•
Hormones are chemical messengers that are produced in one cell or tissue and modulate
cellular processes in another cell by interacting with specific protein receptors. (可以去隔壁聊
八卦的東西叫賀爾蒙)
– Auxins : the growth hormone
– Gibberelins: Regulators of plant height and seed germination
– Cytokinins: Regulators of cell division
– Ethylene: The gaseous hormone
– Abscisic acid: A seed maturation and antistress signal
– Brassinosteroids: steroid hormones
– Others: jasmonic acid, salicylic acid, polypeptide system
Auxin:
the first growth hormone to be discovered in
plants (1832-1926)
¤ Plant cell expansion
¤ Viability
¤ Stem elongation
¤ Apical dominance
¤ Root initiation
¤ Fruit development
¤ Oriented, tropic growth or phototropism
The active growth-promoting substance can diffuse into gelatin block
(1926)
Bioassay: a measurement of the effect of a known or suspected biological
active substance on living material.
A chemiosmotic model (化學滲透模式)– drives polar transport
Auxin pKa= 4.75
proton motive force (PMF)
AUX
IAA用IAAH及IAA-兩種
不同的型態進入細胞
中間一點都不酸~IAA-感
到”溫馨”
外面很酸因為有H+-ATPase
PIN
下面有一群人口販子(PIN)
會把感到溫馨的IAA-一拳
打飛出細胞
A chemiosmotic model – auxin polar transport
Auxin influx (or uptake)
(a) passive diffusion: protonated IAAH
(b) secondary active transporter: 2H+-IAAsymporter.
The efficiency is greater than simple diffusion
AUX1, a permease-type auxin uptake carrier
(aux1 mutant: agravitropic)
AUX
LAX
GA stimulate cell elongation and cell division
•
Modifying cell wall properties
•
Regulate the transcription of cell cycle
kinases. (影響細胞週期)
•
Auxin promotes GA biosynthesis and signal. (
受IAA影響)
•
Rapid stem elongation occurs in rice in
response to flash flooding. (淹水逃命用)
•
The submergence-tolerance is directly linked
to the persistence of DELLA proteins, which
reduces GA sensitivity. (耐淹水的對GA不敏感)
GA regulates the transcription of
cell cycle kinases
1. In the submergence-induced plants, GA
activates the transition from G1 to S
phase, leading to an increase in mitotic
activity. (GA可以加快G1到S)
2. GA induces expression of the genes for
several cyclin-dependent protein kinase
(CDK). (GA增加被始亂終棄的蛋白質)
Cytokinins effects on other physiological
and development processes
•
Leaf senescence
•
Nutrient mobilization
•
Apical dominance
•
Formation and activity of shoot apical meristems
•
Floral development
•
Breaking of bud dormancy
•
Seed germination
•
Light-regulated development
– Chloroplast differentiation
– Autotrophic metabolism
– Leaf and cotyledon expansion
Aged or autoclaved herring sperm DNA had a
powerful cell division-promoting effect
Cytokinins regulate specific components
of the cell cycle
Cdc25 like phosphatase
1. Zeatin levels peak in synchronized culture
tobacco cells at the end of S phase, the
G2/M phase transition, and in late G1. (三個
cytokinin出現的時間點)
2. Cytokinin regulates cell cycle in G2/M
phase transition by activation of cdc25
like phosphatase. (拔人家的P)
3. Cytokinin regulates cell cycle in G1 phase
CYCD3
by regulating expression of CYCD3.
ABA
1. ABA is transported by both the xylem and the phloem, but rich in phloem sap.
2. ABA synthesized in the roots can be transported to the shoot via the xylem.
3. ABA acts as a root signal that helps reduce the transpiration rate by closing stomata in leaves.
4. Stomatal conductance is often much more closely related to soil water status than to leaf water
status, and the only plant part that can be directly affected by soil
water status is the root system.
5. ABA redistribution – “anion trap” concept the steepness of the
pH gradients across membrane the specific uptake carriers.
Redistribution of ABA in the leaf resulting from
alkalinization of the xylem sap during water stress
Discover of ethylene
1. In 19th coal gas was used for street illumination. The
serious defoliation of trees closing street-lamp. (街燈造
成路樹死亡)
2. In 1901, Dimitry Neljubov, a graduate student in Russia
observed that dark-grown pea seedlings in the labotory
air from coal gas exhibited symptom termed Triple
response. (俄國研究生發現的三項反應)
3. Triple response: reduced stem elongation, increased
lateral growth (swelling), abnormal and horizontal
growth. (變矮變胖又變寬)
CK
10 ppm ethylene
Ethylene biosynthetic pathway and
the Yang cycle
1.
The methionine is the precursor of ethylene.
2.
The immediate precursor of ethylene is ACC (1-aminocyclopropane-1-carboxylic acid)
3.
The rate-limiting step: ACC synthase . (最重要的一步靠他)
(unstable and induced by auxin, wounding and fruit ripen)
4.
The last step: ACC oxidase. (最後一步的酵素)
Require Fe2+ and ascorbate for activity
5.
The CH3-S group of methionine is recycled via Yang cycle. (楊氏循環)
6.
Under anaerobic condition, ethylene was not produced from the methionine and ACC accumulated
in the tissue
7.
Conjugation: ACC can also be converted to a conjugated form N-malonyl ACC
Development and physiological
effects of Ethylene
•
Ethylene promotes the ripening of some fruits. (果實後熟)
•
Ethylene induces lateral cell expansion. (細胞橫向生長)
•
The hooks of dark-growing seedling are maintained by ethylene production. (讓頭可以繞圈圈)
•
Ethylene break seed and bud dormancy in some species. (打破休眠)
•
Ethylene promotes the elongation growth of submerged aquatic species. (水生植物生長)
•
Ethylene induces the formation of roots and root hairs. (根毛生長)
•
Ethylene induces flowering in the pineapple family and mango. (鳳梨你個芒果)
•
Ethylene enhances the rate of leaf senescence. (葉子老的化)
•
Some defense response are mediated by ethylene (jasmonic acid). (抗病)
•
Ethylene regulated changes in the abscission layer that cause abscission. (離層產生)
Thanks for your attention!