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欣欣向榮-植物的生長與發育

Plant Growth and Development

清華大學生命科學系

林彩雲

December 5, 2009

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現在所有動物包括人類都屬於複雜生物鏈中消費者的角色，消費者並不能直接將無機分子轉變為含有能量的有機分子所以無法自給自足，必須藉由攝取其他消費者，或生產者也就是光合生物如植物以獲得能量生長。

植物在都市水泥叢林中扮演重要的調和角色，公園又稱為都市之肺，為都市居民平日休憩場所，美化市容也為都市帶來清新的氣息。

森林為野生動物的棲所，和人類生活亦息息相關，假日提供森林浴的最佳場所，其完整的植被可保育國土，林地下蘊藏的水分更是缺水季節水庫重要水源。

植物的種子擔負著傳宗接代的重責大任，其豐富的養分足以供給下一代萌發，也成為人類不可或缺的糧食及生活調劑品來源。

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草本

鬱金香為荷蘭的國花，經過四百多年的育種改良，除擁有品種專利，其生產管理及病蟲害防治等栽培技術均獨步全球，其切花與種球之生產、外銷居世界首位。鬱金香種球培養過程需要夏季冷涼的氣候環境，台灣大部分地區並不適宜，花市所見多為進口球莖種植盆花。

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草本

紅花石蒜 (學名Lycorisradiata Herb.) 廣橢圓形的鱗莖具有毒性；葉為窄帶狀，發於秋末落於夏初，葉落而後花開，花期約從7月至9月，是蝴蝶的重要蜜源植物。

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木本

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木本

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Genome Sizes (haploid)

Base pairs Genes NotesPhi-X 174 5,386 10 virus of E. coli

Human mitochondrion 16,569 37

E. coli 4,639,221 4,377 4,290 of these genes encode proteins; the rest RNAs

Arabidopsis thaliana 115,409,949 25,498

Humans 3.3 x 109 ~25,000

Rice 4.3 x 108 ~60,000

Psilotum nudum 2.5 x 1011

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Photosynthesis

RespirationTranspiration

光合作用

呼吸作用蒸散作用

Nutrition養分

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陸生高等植物的光合作用發生於葉肉組織細胞內葉綠體，光反應在葉綠體中的囊狀堆疊構造也就是類囊體進行，葉綠體色素主要吸收紅光及藍光進行反應，綠光區域多不吸收直接反射，所以光合作用旺盛的葉子都是翠綠色。

收集光能反應單元稱為光合系統 (photosystem, PS)，可分為PSI及PSII。吸收的光能匯集於反應中心會驅動一系列的電子傳遞並在類囊體膜的兩側累積電化學梯度 (electrochemical gradient)，PSII最大量吸收光為波長680 nm的光波，其能量將水分解產生電子及氫離子，電子經過電子傳遞鏈到PSI，氫離子累積於類囊體膜內產生電位差，PSI最大量吸收光為波長700 nm的光波，累積的光能經由輔助酵素將電子接受者NADP+還原；類囊體膜的內腔累積電化學梯度經由膜上酵素合成ATP。

光反應最終的產物是ATP與NADPH，這兩種能量分子將光能轉換成可貯藏的化學能用於接下來的碳固定暗反應中，提供碳水化合物合成所必需的能量。

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PhotosynthesisCarbon dioxide + Water + Sunlight = Sugar + Oxygen

6 CO2 + 6 H2O + Energy => C6H12O6 + 6 O2

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Photosynthetic organismsLeaves from higher plants flanked by colonies of photosynthetic purple bacteria (left) and cyanobacteria (right)

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Photosynthesis 光合作用

Electron transfer in the Photosynthetic Membranefrom Robert Carpentier'sweb site

http://www.uqtr.ca/labcarpentier/eng/home_frames.htm

http://www.flickr.com/photos/quench/355627071/

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Photosynthesis 光合作用

http://en.wikipedia.org/wiki/Photosynthesis

http://upload.wikimedia.org/wikipedia/commons/0/0c/Simple_photosynthesis_overview.svg

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暗反應則是在葉綠體基質 (stroma) 中合成醣類，此反應又稱為卡爾文循環 (Calvin cycle)，將大氣中的二氧化碳固定合成碳水化合物，再經由生物體內各種化學反應合成更複雜的有機分子。

卡爾文循環可分為三部分：羧化 (carboxylation)、還原(reduction)、再生(regeneration)。二氧化碳及水進入卡爾文循環與核酮糖-1,5-二磷酸 (ribulose-1,5-bisphosphate, RuBP) 結合生成3-磷酸甘油酸 (3-phosphoglycerate)，經由ATP與NADPH提供能量還原生成甘油醛-3-磷酸(glyceraldehydes-3-phosphate)，並經由ATP供能再生核酮糖-1,5-二磷酸，使循環繼續進行。

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暗反應每固定3個二氧化碳分子可合成一個甘油醛-3-磷酸的醣類分子，需耗9分子ATP與6分子NADPH。Rubisco為催化RuBP羧化的重要酵素，也具有加氧酵素 (oxygenase) 的功能，其氧合作用(oxygenation) 過程稱為光呼吸 (photorespiration)。

氧合作用與羧化作用競爭rubisco酵素同一活化部位，減低光合作用效率。某些植物發展出因應機制，如C4循環和景天酸代謝(CAM)，能在進行羧化的細胞濃縮二氧化碳濃度，以降低光呼吸作用。

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固定CO2

再生RuBP 還原反應

http://en.wikipedia.org/wiki/Photosynthesis

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Increasing CO2 levelsThe light reactions of photosynthesis stop when the sun goes down

However, CO2 fixation can continue as long as ATP and NADPH is available

In cacti and other succulents CO2 uptake by the plant occurs primarily at night

PhotosynthesisCarbon dioxide + Water + Sunlight = Sugar + Oxygen

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C4 and C3 photosynthesis and CAM

In hot and dry conditions, plants will close their stomata to prevent loss of water.

These conditions will cause an increase of photorespiration by the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenaseand decrease in carbon fixation.

http://upload.wikimedia.org/wikipedia/commons/f/f9/HatchSlackpathway.png

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RespirationC6H12O6 + 6 O2 => 6 CO2 + 6 H2O + Energy

GlycolysisTCA cycleElectron transport chain

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http://upload.wikimedia.org/wikipedia/commons/7/74/CellRespiration.svg

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Glycolysis, breakdown glucose to pyruvic acid in cytosol

Oxidation of pyruvic acid to CO2 and H2O in mitochondria

NADH dehydrogenase

succinatedehydrogenase

cytochrome c reductase(cytochrome b-c1 complex)

cytochrome c oxidase

ATP synthase

Outer membrane

Intermembranespace

Inner membrane Cristae

Matrix

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NADH dehydrogenase

succinatedehydrogenase

cytochrome c reductase(cytochrome b-c1 complex)

cytochromec oxidase

ATP synthase

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Comparison of respiration and photosynthesis

Respiration PhotosynthesisEnergy Released Stored

Reactants Glucose CO2 and H2O

Products CO2 and H2O Glucose

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Comparison of respiration and photosynthesis

Respiration PhotosynthesisSource Glucose Light

Types NAD NADP

Carriers of energy rich electrons

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Comparison of respiration and photosynthesis

Products of electron transport

Respiration Photosynthesis

ATP ATP + NADPH

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Comparison of respiration and photosynthesis

ATP synthesis

Respiration PhotosynthesisETC Yes YesPump proton Yes YesProton gradient Yes YesATP synthase Yes Yes

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Evaporation

Condensation Precipitation

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TranspirationTransporting water and minerals from the soil throughout the plant

Cooling the plant through evaporation

Moving sugars and plant chemicals

Maintaining turgor pressure

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Eduard Strasburger′s On construction and function of the conduits in plants, 1891.

Woody stems with their lower end immersed in concentrated solutions of copper sulfate or picric acid and severed by a cut made below the surface of the liquid, will readily suck the solution up.

Immediately upon contact, the poisonous fluid kills all living cells in its way, but the copper or the acid arrive in the transpiring leaves and kill them as well. The uptake of the solution and the loss of water from the dead leaves may continue for several weeks, and new solutions of a different color may be lifted in a dead stem.

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Science 23 September 2005:Vol. 309. no. 5743, p. 1993DOI: 10.1126/science.309.5743.1993

How does a garden grow?

Transpiration

From water absorption through a plant's roots to water vapor lost through its leaves, Tracy Sterling of New Mexico State University and animator Matt Byrnes created a friendly, interactive activity with a playful design.

The animation teaches plant biology basics and offers numerous interactive features, such as changes to environmental conditions that can impact the speed of water movement.

Transpiration: Water Movement Through Plants

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A balancing act

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Environmental Factors Affecting Growth

Light

Temperature

Water

Humidity

Nutrition

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Temperature effects

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Nutrition effects

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Plants in communitiesPlant or landscape ecologySuccessionAvailable light and moisture Competitive weeds thrive AllelopathyRelationships between plants and pollinators, animals, birds, pests, predators

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black walnuts

Plants guard their “personal space" with poisons

Allelopathy

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Plant hormones and growth regulators

Auxin

Gibberellin

Cytokinin

Ethylene

Abscisic acid

Jasmonate

Salicylic acid

Brassinolides

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Auxin caused responsesBending toward a light source (phototropism) Downward root growth in response to gravity (geotropism) Promotion of apical dominanceFlower formation Fruit set and growth Formation of adventitious roots

http://en.wikipedia.org/wiki/Image:IAAII.pnghttp://upload.wikimedia.org/wikipedia/en/f/f7/Redtip9845.jpghttp://upload.wikimedia.org/wikipedia/commons/d/d6/Plastids_types.svghttp://upload.wikimedia.org/wikipedia/commons/6/6f/Arabidopsis_thaliana.jpg

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GibberellinsStimulate cell division and stem elongation

Break seed dormancy

Speed germination

Promote flowering and sex expression

Promote enzyme induction

Enhance leaf and fruit senescence

http://upload.wikimedia.org/wikipedia/commons/a/ac/Gibberellic_acid.svg

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CytokininsStimulate cell division

Affect shoot and root morphogenesis

Involved in chloroplast maturation

Affect cell enlargement and auxiliary bud release

Cytokinins also are used to delay aging and death (senescence)

http://upload.wikimedia.org/wikipedia/commons/b/bb/Zeatin.png

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EthyleneInduces ripening

Causes leaves to droop (epinasty) and drop (abscission)

Promotes senescence

http://upload.wikimedia.org/wikipedia/commons/e/e9/Ethene_structural.svghttp://upload.wikimedia.org/wikipedia/commons/d/d5/Yang-cycle.png

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Abscisic acid (ABA) A general plant-growth inhibitor

Induces dormancy and prevents seeds from germinating

Causes abscission of leaves, fruits, and flowers

Causes stomata to close

http://en.wikipedia.org/wiki/Image:Abscisic_acid_structure.png

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Phytochrome

Pr Pfr Response666 nm

730 nm

Dark reversionDegradation

Regulate the time of flowering based on the photoperiodismand to set circadian rhythms.

Regulates the germination of seeds, elongation of seedlings, the size, shape and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotylhook of dicot seedlings.

http://upload.wikimedia.org/wikipedia/commons/a/a5/Flower_poster_2.jpg

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Critical Terms Used to Describe Circadian Rhythms

(A) Sleep movements of Phaseoluscoccineus. Position of the primary leaves of a seedling at night (left) and during the day (right).

(B) Circadian rhythm of leaf movements of P. coccineusentrained to light/dark cycles and monitored in continuous light. The peaks of the curve represent the night time leaf position.

http://www.plantcell.org/content/vol18/issue4/images/large/pc040980F01_LW.jpeghttp://www.plantcell.org/content/vol18/issue4/images/large/pc040980F02_HT.jpeg

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horizontal above-ground stems (stolons) of the strawberry

leavesornamental plant Bryophyllum

of the common

GraftingTotipotency

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Flowering: conversion of apical meristem into a floral meristem

TemperatureMany annual plants and biennial plants have their time of flowering delayed unless they have undergone a preceding period of wintertime cold (vernalization)

The buds of many species of woody angiosperms found in temperate climates, also need a preceding period of cold weather before they develop into flowers

PhotoperiodPhotoperiod is detected in the leaves

Leaves produce a chemical signal that is transmitted to the apical meristems to start their conversion into floral meristems.

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Structure of the Flower

The ABC Model of Flower Development

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A for the sepals

A, B and E for the petals

B, C and E for the stamens

C and E for the carpels

C, D and E for the ovules

Except for the A function, which is carried out at least partially by members of the APETALA2 transcription factor family, all regulatory functions are performed by the MADS-box family of transcription factors.

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Rationale for stimulating beveragesflavor, feeling of alertness

Caffeine is chemically related to purine bases in DNA

Desirable effects: stimulation of central nervous system, faster heartbeat, constriction of blood vessels, increased respiration rate, suppression of appetite, diuresis

Undesirable effects: headaches on withdrawal, infertility, birth defects, insomnia

http://upload.wikimedia.org/wikipedia/commons/d/d8/Caffeine.svg

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Tea (Camellia sinensis)Processing: Green tea: leaves are steamed, rolled to break cells and release aroma, dried

Black tea: leaves are withered, rolled, fermented(non-alcoholic), dried

Aroma and flavor from essential oils, additional taste from tannins; stimulating effect from caffeine and theophylline

Caffeine levels vary with the type of tea, black most, oolong intermediate, green tea least; also length of brewing will determine the amount of caffeine in a cup of tea

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Stimulating effect from theobromine, chemically related to caffeine

Theobroma cacao

http://www.botanical.com/botanical/mgmh/c/cacao-02-l.jpghttp://www.botanical.com/botanical/mgmh/c/cacao-02a-l.jpg

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