Anatomical Adaptations of Halophytes: A Review of Classic Literature and Recent Findings

349 Pages·2017·27.23 MB·English

by  Marius-Nicușor Grigore, Constantin Toma

Marius-Nicușor Grigore
Constantin Toma
Anatomical
Adaptations
of Halophytes
A Review of Classic Literature and
Recent Findings
Anatomical Adaptations of Halophytes
Marius-Nicușor Grigore (cid:129) Constantin Toma
Anatomical Adaptations
of Halophytes
A Review of Classic Literature and Recent
Findings
Marius-NicușorGrigore ConstantinToma
FacultyofBiology FacultyofBiology
AlexandruIoanCuzaUniversity PlantAnatomy&EcologyLaboratory
Iasi,Romania AlexandruIoanCuzaUniversity
Iasi,Romania
ISBN978-3-319-66479-8 ISBN978-3-319-66480-4 (eBook)
DOI10.1007/978-3-319-66480-4
LibraryofCongressControlNumber:2017951218
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Foreword
When my colleague and good friend, Marius-Nicus¸or Grigore, asked me to write
the Foreword to this book, “Anatomical adaptations of halophytes,” I was
flattered… but I thought I was not the most appropriate person to do so. I have
worked for over 30 years on various aspects of plant development and plant
responses tostress and the last 15 more specifically on salt tolerance mechanisms
in various plant species, including several halophytes. However, I am a plant
biochemist and molecular biologist and I do not consider myself an expert in
plant anatomy … well, let’s be honest: myknowledge of plant anatomy is practi-
callyzero.So,IfeltIhadnothingtosaytothepotentialreadersofthebook,whoI
assumedshouldbemostlybotanistsandplantanatomists.Whilelookingforapolite
waytodeclinetheinvitation,Iglancedatthesepagesthatarenowinyourhands,
dear reader—or, nowadays, more probably on your computer screen—and I
completely changed my mind. The book fascinated me, and I realized that it
could be just as interesting for any scientist working with this amazing group of
salt-tolerantplants,regardlessoftheirparticularfieldofresearch.Whatfollowsare,
therefore, some brief comments from a nonspecialist, addressed to those re-
searchers with various backgrounds and expertise, about a much specialized—
and very special—book, which I believe should be present on the shelves (or
harddisks)ofanylaboratoryinvolvedinthestudyofhalophytes.
Iamnotgoingindetailintothecontentsofthebook,itsscope,ortheauthors’
reasons to write it; I will not even mention the (multiple) definitions of “halo-
phytes,”apartfromthefactthattheyareplantsabletosurviveandreproduceunder
salinityconditionsthatwillkillthevastmajorityofplantspecies.Thereaderscan
lookthemselvesatthepreface,thetableofcontents,ortheintroductionofthebook.
I would like, instead, to frame the study of halophytes in a wider context: as the
mostappropriatemodelstoinvestigatethemechanismsofsalttoleranceinplants—
which should be obvious, despite the opinion of some hardcore plant molecular
biologists (no, this book does not deal with Arabidopsis thaliana). The study of
thesemechanismsisatpresentaveryactivefieldinplantbiologyresearch,because
ofitsunquestionableacademicinterestbutalsoduetoitspracticalimplicationsin
v
vi Foreword
agriculture. Soil salinity is—together with drought—the most important environ-
mental stress factor responsiblefor the reductionofcrop yields worldwide.In the
context of global climate change, increasing scarcity of good-quality water for
irrigation, and population growth, the biotechnological improvement of the salt
toleranceofourcropshasbecomeanurgentneedforthefutureofagricultureand
food production, especially in arid and semiarid regions; this, in turn, requires a
deep knowledge of the mechanisms used by plants to counteract the deleterious
effectsofhighsoilsalinity.Halophytescannotonlycontributebasicknowledgebut
also provide biotechnological tools—salt tolerance genes and salt-induced pro-
moters—which could be eventually used for the genetic improvement of salt
tolerance of our crops. Some of them could even be domesticated to generate
new crops for food, feed, fiber, biofuel production, or other industrial uses. They
wouldbethebasisofa“salineagriculture,”couldbegrowninsalinisedsoils and
irrigated with brackish or sea water, avoiding in this way competition with our
conventional crops for scarce resources: fertile farmland and freshwater for
irrigation.
Coming back to the book itself, there are several aspects that, in my opinion,
makeitspecialandshouldbehighlighted.First,thebookshouldappealtoawide
readership;duetotheirinterestinbasicresearchandpossiblepracticalapplications
—asmentionedabove—halophytesarebeingstudiedfrommanydifferentpointsof
view by researchers with quite different scientific backgrounds: ecologists, bota-
nists, agronomists, plant physiologists, biochemists, and molecular biologists,
manyofthem(especiallythelatter)withlittleknowledge,ifany,ofplantanatomy.
The information contained in this book is organized basically around specific
anatomic adaptations, which represent structural strategies of halophytes to with-
standhighsoilsalinity(succulence,saltglands,Kranzanatomy,etc.),andnotbased
ontaxonomicclassifications,asonecouldexpectforabookofthiskind.Ifindthis
approach very convenient and accessible, particularly for nonspecialists. Those
scientistsinvestigatingthephysiological,biochemical,andmolecularmechanisms
activated in plants, in general, and in halophytes, in particular, in response to salt
stress—Iknowitfrommyownexperience—oftenneglectconstitutivemechanisms
ofdefensebasedonstructuraladaptationsoftheirinvestigatedspecies.Thisbook
canhelpallofustolookatourownresearchwithawiderperspective.Ialsofind
veryinterestingandintellectuallyrewarding(thisisobviouslyapersonalopinion)
thehistoricalapproachunderlyingtheentirebook’scontentsandorganization,with
numerous references to the work of classical botanists—which in other scientific
fieldswouldbeconsidered“ancient”butinplantanatomywillneverbeoutdated.I
would like to point out, especially, the high quality of the (also “classical”) ink
drawings in many of the figures; probably no “modern” micrograph can show
anatomicstructureswithsuchclarityanddetail.
Inatimeof“omics”technologies,fullgenomesequences,DNA“barcodes,”and
Appsthatcansupposedlyidentifyanyplantspeciesfromapicturetakenwithyour
mobilephone,itisgoodtolookbackandacknowledgetheenormouscontribution
Foreword vii
ofclassicalbotaniststoourpresentknowledgeinthisfield.Itisaswellrefreshingto
look at the beauty of nature, also reflected in the anatomic adaptations to salinity
shownhere.Thisis,basically,whatthisbookisabout.
InstituteofPlantMolecularandCellular OscarVicente
Biology(IBMCP,UPV-CSIC)
UniversitatPolite`cnicadeVale`ncia
Valencia,Spain
Preface
Succulence,tracheoidioblasts(spiralcells),saltsecretion,Kranzanatomy,succes-
sive cambia, and bulliform cells represent major anatomical adaptations found in
halophytes;theyaretreatedinthismonographwithanemphasisonliteraturefrom
the end of the nineteenth century and the beginning of the twentieth century. Of
course, the list of adaptations is not exhaustive; other anatomical features in
halophytes may be associated with saline environments. Naturally, the reviewed
literaturehasnopretensiontobecomplete.Actually,partofrecentliteraturemight
be regarded—at first glance—as being repetitive, at least when it refers to purely
anatomicaldescriptiveapproachesinspeciesthathavealsobeeninvestigatedinthe
past. This is an inherent risk in plant anatomy research, and the real challenge
wouldbetofindtherightframeinwhichtointegratethiskindofapproach.
Anotherimportantobservationinrelationtothisbookisthatwetried—asmuch
as possible—to remain close to anatomy and not to go into details of associated
issues emerging from many of the discussed adaptations. For instance, Kranz
anatomy is related to C photosynthetic pathway, and this requires a very sophis-
4
ticatedapproachintermsofphysiology,biochemistry,andpaleo-ecologyofhalo-
phytes.Inthisrespect,aluxuriantliteraturehasbeenproducedinthepast20years,
includingeditedbooksandpublishedpapers—originalandreviews.Ofcourse,our
intention didnotinterfere with these research directions.Thesameis truefor salt
glands, where many results derived from ultramicroscopic observations or are
focused on the ecophysiology of salt secretion. Again, we tried to remain at the
borderofthisapproach.
However,thesetwoexamplesclearlysuggestthattheanatomyofhalophytesisa
refreshing field that opened many advanced research directions, such as plant
ecophysiology,saltstressphysiology,andmolecularapproaches.
Thechapterdedicatedtosalineenvironmentsisintendedonlytofamiliarizethe
reader with several operational terms related to salt areas. This should not be
regarded a soil science chapter, since we are aware that the terminology and
taxonomy of salt-affected soils is very problematic and the strongest evidence is
the multitude of classification systems existing worldwide. Therefore, in this
ix
x Preface
chapter several concepts are discussed, since the chosen terms are largely used in
thebotanicalliterature,especiallyinthatfromthepastdecades.
Because of the specificity of this book, mentioned species were kept in the
genuine nomenclatural state, with no intention to find actual synonyms. This
would have been tricky, especially for species from Chenopodiaceae and
Plumbaginaceae; in addition, consistent with the vision of this book, readers
interested in the history and evolution of plant taxonomy should be invited to
discover by themselves the exciting journey toward—likely—the most romantic
andfruitfulperiodinthehistoryofbotany.
Iasi,Romania Marius-NicușorGrigore
ConstantinToma
Acknowledgements
Wehavetothankseveralpersons:
Oscar Vicente (Instituto de Biolog´ıa Molecular y Celular de Plantas,
UPV-CSIC) was willing to write a Foreword for our book. In the past, he helped
me very much to integrate in his research group from UPV, giving me the possi-
bility to work and extend my research interests in halophytes. Our collaboration
was and still is very fruitful, and I’m deeply indebted to him for all the support
during the last 7 years. Together with Monica Boscaiu (Instituto Agroforestal
Mediterra´neo, UPV), we managed to create a strong research interest network
betweenRomaniaandSpain.
UniversidadPolite´cnicadeValencia(UPV)hostedmethreetimesatInstitutode
Biolog´ıaMolecularyCelulardePlantas,fordevelopingscientificmissionsrelated
to the study of halophytes. Two stays were funded by COST Action FA0901:
“Putting Halophytes to Work—From Genes to Ecosystems,” in a frame of Short-
Term Scientific Missions. One stay was funded by Universidad Polite´cnica de
ValenciathatsupportedmeintheanatomicalstudyofSpanishhalophytes.During
thesestays,Ihadtheexcellentopportunitytocollectalargenumberofhalophytes,
which were anatomically investigated. Part of the obtained results is included in
thisbook.
COSTActionFA0901:“PuttingHalophytestoWork—FromGenestoEcosys-
tems”alsofundedmeforattendingameetinginTorun(Poland),whenIcollected
twohalophytespeciesfromsalt-affectedareas,duringafieldtrip.Onthisoccasion,
IthankAgnieszkaPiernik(NicolausCopernicusUniversity,Torun)andAlexander
Fehe´r(SlovakUniversityofAgriculture,Nitra,Slovakia)forhelpingmeidentify-
ingseveraltaxainthefield.
Surveyandanalysisofoldbotanicalliteraturerepresentapivotalaspectforthis
book. Not all the bibliographic references were available to us. A part of old
papers—thatwasnotonourdisposal—hasbeenprovidedbyfewpersons.Roberta
Gasparrifromthe DepartmentofAgricultural, FoodandEnvironmentalSciences,
MarchePolytechnicUniversity(Ancona,Italy),sentusLicopoli’spapers.
xi