/\/A/fz#/ ^ *"/ S HISTOLOGICAL INVESTIGATIONS OF THE SECONDARY PHLOEM OF GYMNOSPERMS R. W. DEN OUTER N08201,41 1 WAGENINGEN 582.42/.47:581.824.2 634.0.174.2:634.0.168 HISTOLOGICAL INVESTIGATIONS OF THE SECONDARY PHLOEM OF GYMNOSPERMS PROEFSCHRIFT TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE LANDBOUWKUNDE OP GEZAG VAN DE RECTOR MAGNIFICUS, IR. F. HELLINGA, HOOGLERAAR IN DE CULTUURTECHNIEK, TE VERDEDIGEN TEGEN DE BEDENKINGEN VAN DE SENAAT VAN DE LANDBOUWHOGESCHOOL TE WAGENINGEN OP VRIJDAG 23 JUNI 1967 TE 16.00 UUR DOOR R. W. DEN OUTER H. VEENMAN & ZONEN N.V. - WAGENINGEN - 1967 STELLINGEN I De differentiatie van het vertikale systeem van de bast, loopt parallel met de reductie van de baststralen. Dit proefschrift II De eiwitcellen in debas t van het Chamaecyparispisifera type,vertone n meer overeenkomst metd e begeleidende cellen vand e Angiospermen, dan de eitwitcellen in de bast van hetPseudotsuga taxifolia type. Dit proefschrift III Deter mmergstrale n moet uitsluitend gebruikt worden voor primaire stralen, terwijl secundaire stralen, baststralen genoemd moeten worden, wanneerzi j in het secundaire phloeem voorkomen en houtstralen wanneer zij in het secun­ daire xyleem voorkomen. IV Bij de bast van Gymnospermen is, in tegenstelling met de bast van Angio­ spermen, de mate van aanwezigheid van bastvezels karakteristiek voorhe t ontwikkelingsstadium van het vertikale systeem. ZAHUR, M.S., Cornell Univ. Agr. Exp. St. Mem. 358 (1959) V De opvatting van STRASBURGERda tstippel stusse neiwithoudende -e nzetmeel - houdende systemen zouden ontbreken, isgebleke n onjuist te zijn. STRASBURGER, E., Ober denBa u undde nVerrichtunge n der Leitungsbahnen inde n Pfianzen. Jena (1891) VI De criteria, welke GREGUSS aanlegt bij de rangschikkingvan de houtstralen van de Gymnospermen in verschillende ontwikkelingsstadia, gelden niet voor de baststralen. GREGUSS, P., Xylotomische Bestimmung der heute lebenden Gymnospermen. Budapest (1955) Proefschrift van R.W.DEN OUTER Wageningen, 23jun i 1967. VII Bij de indeling in typen, zijn bij de bast de stralen wel van belang en bij het hout niet. Dit proefschrift VIII De Vaccinium fase van het Dicranum vegetatietype, welke volgens MEISEL- JAHN o.a. ontstaat na bebossing van door anthropogene invloeden uit het Querceto-Betuletum ontstane heidevelden met Pinus sylvestris, doorloopt maximaal 5 en niet 4 stadia. MEISEL-JAHN, S., Angewandte Pflanzensoziologie; Die Kiefern- Forstgesellschaften des Nordwestdeutsche Flachlandes (1955) IX De „topsterfte" in Pinus sylvestris bossen in Nederland heeft als voornaam- ste oorzaak het niet aangepast zijn van deze houtsoort aan het hier te lande heersende klimaat. X De verkeersveiligheid in Nederland kan verhoogd worden, indien de Ver- zekeringsmaatschappijen zouden weigeren ingevoerde tweedehands wagens te verzekeren. CONTENTS 1. INTRODUCTION 1 2. MATERIAL AND METHODS 3 2.1. Slides 3 2.2. Drawings 5 2.3. Termsuse d 5 3. THE DIFFERENT CELL TYPES IN THE SECONDARY PHLOEM 9 3.1. Thecambiu m cells 9 3.1.1. Fusiform cambium initials 9 3.1.2. Rayinitial s 9 3.2. Sievecell s . 10 3.3. Parenchymatous elements 12 3.3.1. Phloem parenchyma 12 3.3.2. Rayparenchym a cells 13 3.4. Sclereidsan d stonecell s 14 3.5. Albuminous cells 15 3.6. Phloemfibres 16 3.7. Periderm 17 4. DISTRIBUTION AND ARRANGEMENT OF CELL TYPES IN THE AXIAL SYSTEM OF THE SECONDARY PHLOEM 18 4.1. Sievecells 18 4.1.1. Sievecell sarrange d inbroa d bands 18 4.1.2. Sievecell sarrange d intotangentia l bands 19 4.1.3. Sievecell sarrange d into tangentiallayer so fon ecel lwid e 19 4.2. Theparenchym a cells . .• 19 4.2.1. Scattered amongsiev ecell s 19 4.2.2. In tangential bands 19 4.2.3. In layerso f onecel lwid e 20 4.3. Thealbuminou s cells 20 4.4. Thephloe mfibre s 21 4.4.1. Scattered amongparenchym a cells 21 4.4.2. Arranged intangentia l layers, 1 cellwid e 21 4.4.3. Arranged intangentia l bands,2- 3 cellswid e 21 4.5. Growthring s 21 5. THE PHLOEM RAYS AND THE WOOD RAYS 23 5.1. The phloem rays 23 5.1.1. Structure 23 5.1.2. Development 23 5.1.3. Phylogeneticstage s 24 5.2. Thewoo dray s 26 5.2.1. Structure 26 5.2.2. Development 26 6. THE TYPES OF THE SECONDARY PHLOEM, BASED ON ARRANGEMENTS OF CELL TYPES 28 6.1. Secondary phloem consisting of broad bands of sieve cells (Pseudotsuga taxifoliatype ) 28 6.1.1. Pit-contact between sievecell san d phloem raysvi ath ealbuminou s cells ... 28 6.1.1.1. PseudotsugataxifoliaBRm 28 6.1.1.2. Pinussylvestris L 31 6.1.1.3. Larix decidua MILL 32 6.1.1.4. Abiesconcolor HOOPES 33 6.1.2. Pit-contact between sieve cells and all the elements of the phloem ray (Tsuga canadensissubtype ) 34 6.1.2.1. Tsugacanadensis CARR 34 6.1.2.2. CedruslibaniA.RICH 34 6.1.2.3. Piceaspec 35 6.2. Secondary phloem consisting of bands of sieve cells and bands of paren­ chymacell s(Ginkgo biloba type ) 36 6.2.1. Ginkgobilobat 36 6.2.2. Podocarpusnerifolius D . DON 37 6.2.3. Taxusbaccata L 38 6.3. Secondary phloem consisting of a regular sequence of alternating cell types (Chamaecyparispisifera type ) 39 6.3.1. Chamaecyparispisifera^NDL. var.plumosa OTTO 40 6.3.2. Thujaplicata LAM B 41 6.3.3. Thujopsisdolabrata SIEB.e tZuc c 42 6.3.4. Taxodiumdistichum A . RICH 42 6.3.5. Cryptomeriajaponica~D.T>ON 43 7. THE PHYLOGENETIC STAGES OF THE BAST TYPES 45 7.1. Comparison ofth estructur e ofth edifferen t secondaryphloe m types .... 45 7.2. Characteristics of the different phylogeneticstage s . 46 7.3. Thedifferen t phylogeneticstage s . 46 8. DISCUSSION 52 8.1. Axial system 52 8.2. Albuminous cellsan d companion cells 53 8.3. Sieveelement s 56 8.3.1. Cytologicspecializatio n 56 8.3.2. Morphologic specialization 57 9. SUMMARY 58 ACKNOWLEDGEMENTS 61 SAMENVATTING 62 REFERENCES 65 PLATES 72 This thesisi s also published as MededelingenLandbouwhogeschoo l Wageningen 67-7(1967 ) (Communications Agricultural University) 1. INTRODUCTION To gain an insight into the structure of the secondary phloem of Gymno- sperms, primarily the different cell types with regard to their appearance, differentiation and degree of development, have to be described. Special atten­ tion has been paid to the presence or the absence of pits, i.e. the location of connections between adjacent cells; in particular amount, kind and location of these pits have been examined. Through these pits an easy movement of assim­ ilatesfro m onecel lt oanother ,i spossible . The term 'pit' isuse d in a broad sense,tha t ist o indicate a cavity or a thin place in the cell wall. In primary walls such pits will also be called 'primary pit-fields'. More specifically, the cavities in parenchyma-cell wallswil lb ecalle d pits, those in sieve-cell walls, between adjacent sieve cells, will be called sieve areas. Consequently the cell types are dependent upon pit-contact between these cells for food-conducting functions. The different arrangements of these cell types are investigated, also the directions in which this movement of assimilatesma ytak eplace . Manystatement s havebee nmad eabou t food-conduction pathways.Th ewa y in which the main transport of food is directly related to the arrangement and the structure of the cell types and the importance of special combinations of different kinds of cell types, have been pointed out. Thus, apart from the comparative anatomy, some physiological aspects have also been alluded to. All these statements about food-conducting pathways require evidence from experiments with tracers etc. Soi n this thesis only a cytological basis for phys­ iologicalinvestigation sha sbee ncreated . Further both the interrelationship between the different cell types and the combination ofthei r occurrence have been studied. An attempt has been made to classify the Gymnosperms into a small number of different types, based on thecharacteristi c structure ofthei r secondaryphloem .Thoug h the arrangement of the cells in the different Gymnosperms varies widely, each of these species belongs to one of the main types or is to be considered as an intermediate between two of those types. The phloem rays turned out to be most important inclassifyin g thevariou sphloe mtypes ,i ncontras twit hth ewoo drays . The different types of secondary xylemar e arranged and classified in viewo f dead elements: tracheids, libriform fibres and vessel members. These are determining for a specialwoo d species;the y are,excep tfo r thelibrifor mfibres, essentialt oth ewater-conductin g function ofth exylem . Theseelement sdevelop , differentiate and modify in the course of time, according to the changing ecologicsituations . The living part of the wood, the parenchymatouspar t andth ewoo d raysi n particular, also develop, but they are not essential to the vertical water- conducting systembu tthe y provide for the horizontal conduction ofwate r and assimilates. Thewoo d raysar eno t interrelated and they do not interfere with the dead cells,whic h aredeterminin g for a specialtyp e ofwoo d species.There - Meded. Landbouwhogeschool Wageningen 67-7(1967) 1 fore thewoo d rays are not essential in classifying woody species into several evolutionary stages, if only the wood is considered. This is entirely different with the phloem, which is mainly composed of living cells.I t is a close, complex and active system; one of its functions is the conduction ofassimilates ,mainl yb yth e sievecells ,throughou t the plant body; here the living phloem rays play a prominent part. A classification of the different Gymnosperm woods, based on the structure ofth e secondary phloem, ishardl ypossibl ewithou t consideringth ephloe mrays . Though it will appear that the phloem rays and the axial system of the phloem show different evolutionary trends, the former are still essential to the classification as mentioned above.Apar t from the rays and the axial system of the secondary phloem, the so-called 'Strasburger albuminous cells' are also important inthi sconnection .