Plant Physiological Ecology Second Edition Hans Lambers F. Stuart Chapin III Thijs L. Pons Plant Physiological Ecology Second Edition 1 3 HansLambers F.StuartChapinIII TheUniversityofWesternAustralia UniversityofAlaska Crawley,WA Fairbanks,AK Australia USA [email protected] [email protected] ThijsL.Pons UtrechtUniversity TheNetherlands [email protected] ISBN:978-0-387-78340-6 e-ISBN:978-0-387-78341-3 DOI:10.1007/978-0-387-78341-3 LibraryofCongressControlNumber:2008931587 #2008SpringerScienceþBusinessMedia,LLC Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewrittenpermissionofthe publisher(SpringerScienceþBusinessMedia,LLC,233SpringStreet,NewYork,NY10013,USA),exceptforbriefexcerpts inconnectionwithreviewsorscholarlyanalysis.Useinconnectionwithanyformofinformationstorageandretrieval, electronicadaptation,computersoftware,orbysimilarordissimilarmethodologynowknownorhereafterdevelopedis forbidden. Theuseinthispublicationoftradenames,trademarks,servicemarks,andsimilarterms,eveniftheyarenotidentifiedas such,isnottobetakenasanexpressionofopinionastowhetherornottheyaresubjecttoproprietaryrights. Printedonacid-freepaper springer.com Foreword to Second Edition Inthedecadethathaspassedsincethefirsteditionofthisbook,theglobalenviron- menthaschangedrapidly.Eventhemoststeadfast‘‘deny-ers’’havecometoaccept thatatmosphericCO enrichmentandglobalwarmingposeseriouschallengesto 2 life on Earth. Regrettably, this acceptance has been forced by calamitous events ratherthanbythelong-standing,soberwarningsofthescientificcommunity. Thereseemstobegrowingbeliefthat‘‘technology’’willsaveusfromtheworst consequencesofawarmerplanetanditswaywardweather.Thishope,thatmayin theendprovetobenomorethanwishfulthinking,relatesprincipallytothebuilt environmentandhumanaffairs.Alternativesourcesofenergy,utilizedwithgreater efficiency,areattheheartofsuchhopes;evenalternativewaysofproducingfoodor obtainingwatermaybepossible.Forplants,however,thereisnoalternativebutto utilize sunlight and fix carbon and to draw water from the soil. (Under a given rangeofenvironmentalconditions,theseprocessesarealreadyremarkablyefficient byindustrialstandards.)Canwe‘‘technologize’’ourwayoutoftheproblemsthat plantsmayencounterincapricious,stormier,hotter,drier,ormoresalineenviron- ments?Climatechangewillnotalterthebasicnatureofthestressesthatplantsmust endure,butitwillresultintheiroccurrenceinplaceswhereformerlytheirimpact wassmall,thusexposingspeciesandvegetationtypestomoreintenseepisodesof stressthantheyareabletohandle.Thetimescaleonwhichtheclimateischangingis toofasttowaitforevolutiontocomeupwithsolutionstotheproblems. For a variety of reasons, the prospects for managing change seem better in agriculturethaninforestsorinwildplantcommunities.Itispossibletointervene dramaticallyinthenormalprocessofevolutionarychangebygeneticmanipulation. Extensive screening of random mutations in a target species such as Arabidopsis thalianacanrevealgenesthatallowplantstosurviverathersimplifiedstresstests. This is but the first of many steps, but eventually these will have their impact, primarilyonagriculturalandindustrialcrops.Thereisahugeresearcheffortinthis areaandmuchoptimismaboutwhatcanbeachieved.Muchofitisdonewithlittle referencetoplantphysiologyorbiochemistryandhasacuriouslyempiricalchar- acter.Onecansensethatthereisimpatiencewithplantphysiologythathasbeentoo slowindefiningstresstolerance,andabeliefthatifagenecanbefoundthatconfers tolerance, and it can be transferred to a species of interest, it is not of prime v vi ForewordtoSecondEdition importance to know exactly what it does to the workings of the plant. Such a strategyismoredirectedtowardoutcomes thanunderstanding, eventhoughthe technologyinvolvedissophisticated.Isthereaplaceforphysiologicalecologyin theneworderofthings?Theanswerisperhapsaphilosophicalone.Progressover the centuries has depended on the gradual evolution of our understanding of fundamental truths about the universe and our world. Scientific discovery has always relished its serendipitous side but had we been satisfied simply with the outcomesoftrialanderrorwewouldnotbewherewearetoday. It is legitimate to ask what factors set the limits on stress tolerance of a given species.Toanswerthisonemustknowfirsthowtheplant‘‘works’’;ingeneral,most ofthisknowledgeistohandbutisbasedonarelativelyfewmodelspeciesthatare usuallychosenbecauseoftheeasewithwhichtheycanbehandledinlaboratory conditionsorbecausetheyareeconomicallyimportant.Aswellasdescribingthe basicphysiologyofplantstheauthorsofthisbooksetouttoanswermoredifficult questions about the differences between species with respect to environmental variables. The authors would be the first to admit that comprehensive studies of comparative physiology and biochemistry are relatively few. Only in a few instances do we really understand how a species, or in agriculture, a genotype, pullsoffthetrickofsurvivingorflourishinginconditionswhereotherplantsfail. Ofcourse,theabovehasmorethanhalfaneyeonfeedingtheincreasingworld population in the difficult times that lie ahead. This has to be every thinking person’sconcern.Thereis,however,moretoitthanthat.Largeecosystemsinteract withclimate,theoneaffectingtheother.Itwouldbeasrash,forexample,toignore theeffectsofclimatechangeonforestsasitwouldbetoignoreitseffectsoncrops. Thereismoretothesuccessfulexploitationofagivenenvironmentthancanbe explainedexclusivelyintermsofaplant’sphysiology.Animportantthrustinthis bookistheinteraction,oftencrucial,betweenplantsandbeneficial,pathogenicor predatory organisms that sharethat environment.Manipulation of these interac- tions is the perennial concern of agriculture either directly or unintentionally. Changesintemperatureandseasonalityalterestablishedrelationsbetweenorgan- isms, sometimes catastrophically when, for example, a pathogen or predator expands its area of influence into plant and animal populations that have not beenexposedtoitpreviously.Understandingsuchinteractionsmaynotnecessarily allow us to avoid the worst consequences of change but it may increase our preparednessandourchancesofcomingupwithmitigatingstrategies. DAVIDT.CLARKSON OakHouse Cheddar,UK January2008 About the Authors Hans Lambers is Professor of Plant Ecology and From1979 to 1982, he worked as a postdoc at The Head of School of Plant Biology at the University UniversityofWesternAustralia,MelbourneUniver- ofWesternAustralia,inPerth,Australia.Hedidhis sity,andtheAustralianNationalUniversityinAus- undergraduatedegreeattheUniversityofGronin- tralia, working on respiration and nitrogen gen,theNetherlands,followedbyaPhDprojecton metabolism.AfterapostdocathisAlmaMater,he effects of hypoxia on flooding-sensitive and flood- becameProfessorofEcophysiologyatUtrechtUni- ing-tolerant Senecio species at the same institution. versity,theNetherlands,in1985,wherehefocused on plant respiration and the physiological basis of variationinrelativegrowthrateamongherbaceous plants.In1998,hemovedtotheUniversityofWes- tern Australia, where he focuses on mineral nutri- tion and water relations, especially in species occurring on severely phosphorus-impoverished soils in a global biodiversity hotspot. He has been editor-in-chiefofthejournalPlantandSoilsince1992 and features on ISI’s list of highly cited authors in thefieldofanimalandplantsciencessince2002.He waselectedFellowoftheRoyalNetherlandsAcad- emyofArtsandSciencesin2003. F.StuartChapinIIIisProfessorofEcologyatthe Institute of Arctic Biology, University of Alaska Fairbanks, USA. He did his undergraduate degree (BA)atSwarthmoreCollege,PA,UnitedStates,and then was a Visiting Instructor in Biology (Peace Corps)atUniversidadJaveriana,Bogota,Columbia, from1966to1968.Afterthat,heworkedtowardhis PhD, on temperature compensation in phosphate absorption along a latitudinal gradient at Stanford University,UnitedStates.HestartedattheUniver- sityofAlaskaFairbanksin1973,focusingonplant mineral nutrition, and was Professor at this vii viii AbouttheAuthors institution from 1984 till 1989. In 1989, he became ProfessorofIntegrativeBiology,UniversityofCali- fornia, Berkeley, USA. He returned to Alaska in 1996. His current main research focus is on effects of global change on vegetation, especially in arctic environments. He features on ISI’s list of highly rice. Back at Utrecht University, he worked on the cited authors in ecology/environment, and was ecophysiologyofseeddormancyandgermination. elected Member of the National Academy of From the late 1980s onward he focused on photo- Sciences,USAin2004. syntheticacclimation,includingenvironmentalsig- naling in canopies. He spent a sabbatical at the University of California, Davis, USA, working ThijsL.PonsrecentlyretiredasSeniorLecturer withBobPearcyoneffectsofsunflecks.Hisinterest in Plant Ecophysiology at the Institute of Environ- inphotosyntheticacclimationwasexpandedtotro- mental Biology, Utrecht University, the Nether- picalrainforestcanopieswhenhebecameinvolved lands.HedidhisundergraduatedegreeatUtrecht in a project on the scientific basis of sustainable University,theNetherlands,wherehealsoworked forest management in Guyana, from 1992 to towardhisPhD,onaprojectonshade-tolerantand 2000. He is associate editor for the journal Plant shade-avoidingspecies.HeworkedinBogor,Indo- Ecology. nesia,from1976to1979,onthebiologyofweedsin Foreword to First Edition Theindividualisengagedinastruggleforexistence(Darwin).Thatstrugglemaybe oftwokinds:Theacquisitionoftheresourcesneededforestablishmentandgrowth fromasometimeshostileandmeagerenvironmentandthestrugglewithcompeting neighborsofthesameordifferentspecies.Insomeways,wecandefinephysiology andecologyintermsofthesetwokindsofstruggles.Plantecology,orplantsociol- ogy,iscenteredontherelationshipsandinteractionsofspecieswithincommunities andthewayinwhichpopulationsofaspeciesareadaptedtoacharacteristicrange ofenvironments.Plantphysiologyismostlyconcernedwiththeindividualandits struggle with its environment. At the outset of this book, the authors give their definitionofecophysiology,arrivingattheconclusionthatitisapointofviewabout physiology. A point of view that is informed, perhaps, by knowledge of the real world outside the laboratory window. Aworld in which, shall we say, the light intensityismuchgreaterthanthe200–500mmolphotonsm(cid:2)2s(cid:2)1usedintoomany environmentchambers,andoneinwhichaconstant208Cdayandnightisagreat rarity. The standard conditions used in the laboratory are usually regarded as treatments. Of course, there is nothing wrong with this in principle; one always needsabaselinewhenmakingcomparisons.Theidea,however,thatthelaboratory controlisthenormisfalseandcanleadtomisunderstandingandpoorpredictions ofbehavior. Theenvironmentfromwhichmanyplantsmustacquireresourcesisundergoing changeanddegradation,largelyasaresultofhumanactivitiesandtherelentless increaseinpopulation.Thishasthrownthespotlightontothewayinwhichthese changesmayfeedbackonhumanwell-being.Politiciansandthegeneralpublicask searching questions of biologists, agriculturalists, and foresters concerning the future of our food supplies, building materials, and recreational amenities. The questions take on the general form, ‘‘Can you predict how ‘X’ will change when environmentalvariables‘Y’and‘Z’change?’’Therecentexperienceofexperimen- tation,doneathighpublicexpense,onCO enrichmentandglobalwarming,isa 2 soberingreminderthatnotenoughisknownabouttheunderlyingphysiologyand biochemistry of plant growth and metabolism to make the confident predictions thatthecustomerswanttohear.Evenatthelevelofindividualplants,thereseems tobenoclearprediction,beyondthattheresponsedependsonspeciesandotherill- defined circumstances. On the broader scale, predictions about the response of ix x ForewordtoFirstEdition plantcommunitiesareevenhardertomake.Inthepublicmind,atleast,thisisa failure.Theonlywayforwardistoincreaseourunderstandingofplantmetabolism, of the mechanisms of resource capture, and the way in which the captured resourcesareallocatedtogrowthorstorageintheplant.Tothisextent,Icansee nodistinctionbetweenplantphysiologyandecophysiology.Therearelargenum- bersofmissingpiecesofinformationaboutplantphysiology—period.Theapproach ofthenewmillennium,then,isagoodtimetorecognizetheneedtostudyplant physiologyanew,bringingtobeartheimpressivenewtoolsmadeavailablebygene cloningandrecombinantDNAtechnology.Thisbookistobewelcomedifitwill encourage ecologists to come to grips with the processes which determine the behavior of ‘‘X’’ and encourage biochemistry and physiology students to take a morerealisticviewoftheenvironmentalvariables‘‘Y’’and‘‘Z’’. Thebookstarts,appropriately,withthecaptureofcarbonfromtheatmosphere. Photosynthesisisobviouslythebasisoflifeonearth,andsomeofthemostbrilliant plantscientistshavemadeittheirlife’swork.Asaresult,weknowmoreaboutthe molecular biophysics and biochemistry of photosynthesis than we do about any otherplantprocess.Theinfluenceofvirtuallyeveryenvironmentalvariableonthe physiologyofphotosynthesisanditsregulationhasbeenstudied.Photosynthesis, however, occurs in an environment over which the individual plant has little control.Inbroadterms,aplantmustcopewiththerangeoftemperature,rainfall, light intensity, and CO concentration to which its habitat is subjected. It cannot 2 changethesethings.Itmustrelyonitsflexiblephysiologicalresponsetomitigate theeffectsoftheenvironment.Atalaterstageinthebook,thefocusshiftsbelow ground, where the plant has rather more control over its options for capturing resources. It may alter the environment around its roots in order to improve the nutrientsupply.Itmaybenefitfrommicrobialassistanceinmobilizingresourcesor enter into more formal contracts with soil fungi and nodule-forming bacteria to acquirenutrientresourcesthatwouldotherwisebeunavailableorbeyonditsreach. Towarditsclose,thebookturnstosuchinteractionsbetweenplantsandmicrobes andtothechemicalstrategiesthathaveevolvedinplantsthatassistthemintheir struggleswithoneanotherandagainstbrowsingandgrazinganimals.Theauthors end,then,onafirmlyecologicalnote,andintroducephenomenathatmostlabora- tory physiologists have never attempted to explore. These intriguing matters remind us, as if reminders were needed, of ‘‘how little we know, how much to discover’’(SpringerandLeigh). DAVIDT.CLARKSON IACR-LongAshtonResearchStation UniversityofBristol April1997