Bothalia 15, 3 & 4; 561-566 (1985)
Leaf anatomy o f the South African Danthonieae (Poaceae). X .
Pseudo-pentam eris
R . P. E L L IS ’
K eywords; D a n th o n ie a e , le a f anatom y, Pseudopentameris
A B S T R A C T
T h e leaf b lad e anatom y o f Pseudopentameris macramha (S c h rad .) C o n e rt an d P. brachyphylla (S tap f) C onert w as studied b o th in transection a n d in surface view an d is illu strated b y m eans o f p hotom icrographs. T he le a f an ato m y is typically dan th o n o id . T h e abaxial ep id erm is consists o f in flated , hexagonal long cells and sto m ata and m icro-hairs a re ab sen t. A daxial m icro-hairs w ere o b serv ed . T h e crea tio n o f a n ew genus to accom m odate these tw o spccics a p p ea rs justified b u t c e rtain species in Pentameris B eau v ., Merxmuellera C o n ert a n d Pentaschistis S tapf show sim ilarities t o Pseudopentameris a n d c o n sid eratio n should b e given to th e ir inclusion in Pseudopenta-mem.
IN T R O D U C T IO N
Pseudopentameris C onert was described as re cently a s 1971 to accom m odate two species p re viously placed in Danthonia D C ., namely Pseudo pentameris macramha (S chrad.) C onert and P. bra chyphylla (S tapf) C onert (C o n ert, 1971). D e W et (1956) was also o f th e opinion th a t these tw o species deserved generic rank bu t refrained from describing a new genus as a com plete com parative anatom ical, cytological an d m orphological study o f the genus Danthonia was no t available.
T h e species assigned to Pseudopentameris have 2- flow ered spikelets over 40 mm long and differ co n siderably from all th e o th er South African species previously referred to the genus Danthonia. Several au th o rities, including N ees, Kunth and A dam son (C htppindall, 1955), w ere aw are o f these differences a n d had placed these species in the genus Pentameris B eauv. C onert (1971) notes that Pseudopentameris differs from Pentameris in having m any-nerved glum es, th e caryopsis structure is different and the leaf anatom y is distinct. Chippindall (1955) m entions that th e style is greatly reduced, w hereas in Penta meris, it is short bu t th ere is little else in the spikelet m orphology o f Pseudopentameris macrantha an d P. brachyphylla to suggest affinity with Pentameris.
D e W et (1956) considers Pseudopentameris to be closely related to both Danthonia and Pentameris but C o n ert (1971) is o f the opinion that th e genus occupies an isolated position w ith n o obvious re lationships with o th e r danthonoid grasses. T his opin ion is confirm ed by Renvoize (1981) w ho includes Pseudopentameris in th e peripheral genera o f his A r- undineae which includes all the genera here consid e red as belonging to the D anthonieae. H ow ever, in his m u ltiv ariate analysis Pseudopentameris is g rouped with the ‘c o re’ genera o f the A rundinoi- deae.
P. mucrantha and P. brachyphylla are b o th rath er ro b u st, tufted perennials being easily distinguished from each o th e r by th e pronounced rolling o r curling
* B otanical R esearch In stitu te , D e p artm en t o f A griculture & W a te r S up p ly , P rivate B ag X 101, P reto ria 0001.
of the lower leaves o f P. brachyphylla. The genus is confined to the south-w estern C ape Province from P iketberg in th e north to R iversdale in th e east. P. brachyphylla is very rare and occurs mainly in the H o tten to ts H olland range w here it som etim es occurs together with P. macrantha. P. macrantha is particu larly com m on on th e C ap e Peninsula. B oth species ap p ear to favour sandy habitats at th e base o f hill slopes, o ften in seepage areas b u t, in th e D e H oo p a re a , P. macrantha grows in crevices in lim estone rock.
T he leaf anatom y o f Pseudopentameris has re ceived scant attention in the past. D e W et (1954, I960) rep orted th at the chlorophyll is uniform ly dis trib u ted throughout the m esophyll, bicellular hairs are p resen t, the epiderm is consists o f thin p aren chym a an d the costal silica ceils arc dum b-bell shaped, H e is o f the opinion (D e W et, 1956) th a t the species now included in Pseudopentameris com bine in th eir leaf anatom y th e panicoid type o f epiderm is (with m icro-hairs) and th e festucoid ty pe o f chloro phyll distribution. Renvoize (1981), o n the o th e r han d, considers m icro-hairs to b e absent in Pseudo pentameris bu t does not consider th e genus to belong w ith the pooid grasses because ‘th e subsidiary cells are low dom e-shaped, th e silica bodies are saddle shaped o r oblong and the long cells m ay b e straight o r sinuous-w alled'. T hese featu res favour th e placing o f this genus in the A rundinoideae.
Conflicting rep orts have, th ere fo re , been m ade in th e past regarding the leaf anatom y o f Pseudopenta meris, particularly as far as the presence o r absence o f m icro-hairs is concerned. This p ap e r re p o rts o n a detailed study o f a representative sam ple o f 24 speci m ens, m ost o f which w ere freshly fixed in th e field a n d , as a result, should enable anatom ical character istics to be confidently evaluated in fu tu re consider ations o f th e relationships and taxonom y o f Pseudo pentameris. T he standardized term inology o f Ellis (1976. 1979) is used in the descriptions to g eth er with th e following abbreviations:
vb/s — vascular bundle/s
l ’vb/s — first o rd e r vascular b undle/s
2'v b /s — second o rd e r vascular b undle/s 3’vb/s — th ird o rd e r vascular bundle/s
A N A T O M IC A L D E S C R IP T IO N O F P SEU D O P E N TA M E R IS C O N E R T
L ea f in transverse section
L ea f outline: broadly U -shaped (Figs 2 & 3) with arm s o f lam ina convex (Fig. 1) in P. macrantha: leaves tend to be expanded an d flat in P. brachy- phylla (Figs 14 & 17). Ribs & furrows: sim ilar adax- ial ribs present o v er an d furrow s betw een all vbs; furrow s o f m edium d e p th , eith er cleft-like (Fig. 4) o r m ore o p e n (Figs 5 & 6); ribs with rou n d ed sides and flat tops in both species. No abaxial rib d evelop m ent. Median bundle: not structurally different from o th e r l ’vbs; distinguishable by location only (Figs 1,
14 & 17). Vascular bundle arrangement: always 5 1’vbs in leaf section in P. brachyphylla (Figs 14 & 17) b u t P. macrantha has e ith e r 5 (Fig. 1) o r 7 o r 9 (Figs 2 & 3), T h e arrangem ent o f different o rd ers o f vbs
FIG S 1-7. — Pseudopeniameris macrantha: transverse sections o f th e leaf b lad e. 1—3 , o u tlin e o f th e leaf, x 1 0 0 :1 , Ellis 2526; 2 , Ellis 2512; 3 , Ellis 2515; 4 , lea f m argin s tru c tu re , Ellis 2526, x 250. 5 -7 . d e ta il o f v ascular b u n d les a n d m esophyll: 5 , com pact, isodiam etric ch lo ien ch y m a, Ellis 2338, x 250; 6 , isodiam etric chlorenchym a, Ellis 2515, x 400; 7 , unlignified sclerenchym a g ird ers an d chloroplast a rra n g e m e n t, Ellis 2265, x 400.
B o th alia 15, 3 & 4 (1985) 563
an d slightly thickened walls. Ibs com plete around l ’vbs; cells with uniform ly thickened walls (Figs 5 ,7 , 15 & 16). Sclerenchyma: adaxial girders associated with all 1’vbs; equidim ensional in P. macrantha (Figs 5, 6 & 7) bu t T -shaped in P. brachyphylla (Figs 15 & 16). A baxial g irders equidim ensional in both species. F ibres w ith thickened walls b u t com posed mainly o f cellulose an d d o not stain red with saffra- nin. M argins with rounded sclerenchym a cap in P. macrantha (Fig. 4) but no sclerenchyma developed in association with th e m argin in P. brachyphylla (Figs 14 & 17). Mesophyll: chlorenchym a not ra d iate; consists o f tightly packed, angular, regular, isodiam etric cells (Figs 5 . 6 & 16); these chloren chym a cells w ith characteristic central vacuole with p erip h eral chloroplasts. No colourless cells. Adaxial epidermis: fan-shaped groups o f bulliform cells situ a te d at bases o f furrows, No m acro-hairs, prickles, hooks o r papillae seen but adaxial m icro-hairs com m only visible in transections o f P. brachyphylla (Figs 15 & 16). Abaxial epidermis: n o bulliform cells; con sists o f very conspicuous large, regular, inflated cells w ith o u ter tangential wall slightly thickened. N o a p pendages.
Abaxial epidermis in surface view
Intercostal long cells: usually elongated but som e tim es length is only slightly g re ater than w idth (Fig. 12); side walls always angled o r bow ed outw ards giv ing cells a hexagonal o r inflated appearance; end walls vertical; walls eith er slightly undulating (Fig. 18) o r n o t undulate (Fig. 12) and unthickened. Cell shape an d size is noticeably consistent throughout all intercostal zones. Pairs o f short cells are present be tw een successive long cells. N o abaxial bulliform cells. Stomata: absent on abaxial surface o f b o th P. macrantha and P. brachyphylla in all specim ens exam ined except Ellis 2515 (Fig. 8); low do m e sh ap e d . Intercostal short cells: silico-suberose couples w ith silica cell tall an d narrow w ith sm ooth o utline o r kidney shaped (Figs. 12, 18 & 19); short cell larger th an silica cel! and enfolding it; located betw een virtually all intercostal long cells. Papillae: absent. Prickles & hooks: not present on any p rep aratio n s exam ined. Micro-hairs: not present on abaxial surface. Macro-hairs: absent. Costal silica bodies: equidim ensional to horizontally elongated dum b-bell shaped (Figs 12, 13, 18 & 19); alternate w ith costal long cells; costal zones narrow (3-5 files wide).
Specim ens exam ined:
Pseudopentameris brachyphylla
C A PE , — 3418 (Simonstown): Platberg, Kogetberg Stale Forest (-B D ). Ellis 2343, 2344, Boucher 357a. 3419 (Caledon): Lebanon Forest Reserve, Grabouw (-A A ), Kruger 149;Bredas- dorp (-B D ), A cock, 22476.
Pseudopentameris macrantha
C A PE . — 3218 (Clanwilliam): Versveld’s Pass, Piketberg (-D C ), Ellis 1171. 3318 (Cape Town): Kirstenbosch, Table Mountain (-C D ), Ellis 2308, Sandwiih 73, While 5518; Heuning- vlei, Jonkeishoek (-C D ), Ellis 2265, 2266. 3418 (Simonstown); C ape Point N ature Reserve (-A D ), Eltis 2326, 2327; Cape Hangklip (-B D ), Ellis 2338, 2339;Elephant Rock near Bettys Bay, Cleghorn 2495. 3419 (Caledon): 5 km from KJeinmond on road to Hermanus (-A C ), EUls 2515;10 km from H erm anus on
ro ad to G an sb aai ( - A D ) , Ellis 2512. 3420 (B red asd o rp ); D e H o o p N atu re R eserve ( - A D ) , Ellis 1288, 2526; 5 km fro m W yd- gelegen o n ro a d so D e H o o p , Ellis 1660; B reede R iver m outh
(-B D ), Ellis 1673; 3 km from A rniston o n ro a d to B red asd o rp (- C A ) , Ellis 1274. 3421 (R iversdale): A lbertina ( - B A ) , Ellis 2551.
D ISC U SS IO N A N D C O N C L U S IO N S
T h e contradictory statem ents in th e literature re garding th e presence or absence o f m icro-hairs in Pseudopentameris deserve com m ent in th e light o f the observations o f th e present study. N o m icro hairs were observed on th e abaxial epiderm is o f any o f the 24 specim ens exam ined in th is study an d this observation is in agreem ent w ith th e statem en t by Renvoize (1981) that m icro-hairs are ab sen t. H ow ever, in th e leaf transections o f all the specim ens o f P. brachyphylla, and in m any o f th e sections o f P. macrantha, m icro-hairs are clearly evident on the sides o f th e furrows o f the adaxial epiderm is. (Figs
15 & 16). T he em phasis placed o n th e absence o f m icro-hairs by Renvoize (1981), th ere fo re , is not justified and Pseudopentameris can b e considered as belonging to th e A rundineae to g eth er w ith all the o th e r South African genera previously placed in the D anthonieae. C onsidering it as a p erip h e ral genus, to g eth er w ith th e o th er anom alous arundinoid gen era, is n o longer necessary in th e light o f the obser vations o f th e present study.
This confirm ation o f the presence o f m icro-hairs o n Pseudopentameris agrees with D e W et’s (1954, 1956, 1960) observations. H ow ever, D e W et (1956) considers th e epiderm is o f Pseudopentameris to be panicoid an d sim ilar to th a t o f g enera such as Schis- mus B eauv., Chaetobromus Nees and m any species o f Pentaschistis Stapf. This is n o t th e case, how ever, as Pseudopentameris does not possess num erous abaxial m icro-hairs as d o all the above gen era. T he abaxial epiderm is of Pseudopentameris actually re sem bles that o f Pentameris B eauv. and Merxmuel- lera C o n ert. m ore closely. These are considered as being festucoid by D e W et (1956) an d th e characteri zation o f th e epiderm is o f Pseudopentameris as p a n icoid do es not agree with the observations o f the present study. O f all the South A frican danthonoid gen era, Pseudopentameris resem bles m ost closely Pentameris, Merxmuellera and those Pentaschistis species considered by D e W et (1956) as having the festucoid type o f epiderm is. All these taxa lack abax ial m icro-hairs, costal zones are o ften n o t clearly d e fined and stom ata are o ften absent from this surface.
Superficial m orphological sim ilarities betw een Pseudopentameris and Pentameris undoubtedly exist and N ees, K unth and A dam son considered these two genera to be congeneric (C hippindall, 1955). N um erous m orphological characteristics distinguish these tw o g enera (C hippindall, 1955; D e W et, 1956), how ever, an d C onert (1971) considered these differ ences to be o f sufficient m agnitude to w arran t th e establishm ent o f a new genus. H e is o f th e opinion that no close an d obvious relationship exists betw een Pseudopentameris and any o th er genera known to him.
significantly from th a t o f most Pentameris species and anatom ical indications are that Pseudopentame- ris undoubtedly w arrants sep arate generic statu s and that it occupies a som ew hat isolated phylogenetic position n earest to Pentameris and Merxmuellera. This contention ap p ears to be substantiated by the fact th at th ere are som e species in b o th th e latter genera possessing a large degree o f anatom ical simi larity to Pseudopentameris, indicating a som ew hat interm ediate relationship for Pseudopentameris.
Pentameris dregeana S tapf, P. macrocalycina (S te u d .) S ch w e ic k ., P. obtusifolia (H o c h s t.) Schweick. an d P. thuarii B eauv. show little an ato m
ical sim ilarity to Pseudopentameris. H ow ever, Pen tameris longiglamis (N ees) S tapf an d an undescribed species rep resented by Ellis 2342, Taylor 3023 and Haynes 770, b ea r rath er close resem blances to Pseu- dopentameris. B oth these species have large, in flated abaxial epiderm al cells which are hexagonal in shape in surface view. S tom ata an d m icro-hairs are also absent and the costal zones are som ew hat indis tinct. H ow ever, th e silica bodies are no t dum b-beli shaped as in Pseudopentameris.
B oth these tw o Pentameris specics have been found only in th e C aledon District in th e Kogelberg State F orest. T hey grow to g eth er in th e sam e com
F1GS 8-13..— Pseudopentameris macrantha: abaxial epidermis. 8 -9, arrangem ent o f costal and intercostal zones, x UK). 8, costal and intercostal 2ones overlying first and third order vascular bundles, note presence o f stom ata. Ellis 2515; stom ata absent.
B othalia 15, 3 & 4 (1985) 565
m unity. often also in association with both Pseudo- pentameris brachyphylla an d P. macrantha. T h e un described species, in particular, appears to be in ter m ediate betw een Pentameris longiglumis and Pseu dopentameris and a hybrid origin appears m ost likely. T he spikelet m orphology o f Pentameris longi- glumis requires detailed reassessm ent in o rd e r to es tablish its true relationships with eith er Pentameris o r Pseudopentameris.
In th e genus Merxmuellera th ere is also a group of species which differs significantly from th e rem ain d e r o f the genus in possessing epiderm al long cells with outw ardly bow ed walls. This group includes M. decora (N ees) C o n ert, M. lupulina (T h u n b .) C onert and M. rtifa (N ees) C onert and their anatom y has been described in detail (Ellis, 1983). All these species differ from Pseudopentameris in having abaxial stom ata and m icro-hairs. H ow ever, stom ata are absent from som e specim ens o f Merxmuellera decora an d m icro-hairs are exceedingly rare in all th ree species. It must also be m entioned th a t th e in flated n atu re o f the abaxial long cells is only evident in surface view a n d in transection the epiderm al cells are not as large and inflated as in Pseudopentameris. All the above species d o . how ever, have very little lignin present in th e fibres o f the sclerenchym a gir
ders — a noticeable feature shared with Pseudopen tameris but not with o th er d anth on oid grasses in gen eral.
Finally, Merxmuellera lupidina, in particular, bears a strong anatom ical resem blance w ith Pentas- chistis involuta (S teud.) Adam son an d P. viscidula (N ees) Stapf (Ellis, 1983). T hese species also have inflated epiderm al cells and are exceptional in the genus due to this fact. T hey, th erefo re, deserve con sideration to g eth er with Merxmuellera lupidina and its allies.
A natom ical criteria, th ere fo re , suggest that the above-m entioned Merxmuellera, Pentameris and Pentaschistis species req uire taxonom ic re-evalua- tion in conjunction with Pseudopentameris. T his is essential in o rd e r to establish th e true relationships o f Pseudopentameris an d to define th e limits o f the above g enera. This study o f th e leaf anatom y o f Pseudopemameris fully supports th e creatio n o f a sep arate genus to accom m odate these tw o very closely related species which b ea r little resem blance to th e m ajority o f the taxa previously classified in Danthonia as well as Pentameris an d Pentaschistis. H ow ever, Pseudopentameris does share certain ana tom ical characters with a few species from each o f
FIGS 14-19. — Pseudopentameris brachyphylla: leaf anatom y and epidermal structure. 14-17. leaf in transverse section: 14. outline of leaf, Ellis 2344. x 100: 15. detail o f mesophyll and vascular bundles, note presence o f adaxial micro-hairs (arrowed), Ellis
these gen era b u t th e taxonom ic and phylogenetic significance o f these sh ared characteristics is n o t cer tain a t this stage and aw aits cytogenetical confirm a tion. A possible practical solution, th a t is suggested by the leaf anatom y, is the incorp oraton o f all these taxa with anom alous anatom y in a single genus to g eth er with Pseudopentameris. T his w ould result in the c reatio n o f a g enus, which w ould be anatom ically hom ogeneous, and would be easily distinguishable from all th e o th er S outh A frican d anthon oid genera on the basis o f leaf anatom y.
U IT T R E K S E l
Die anatomiese struktuur van die blaar van Pseu d opentam eris m acrantha (Schrad.) Conert en P. b ra chyphylla <Stapf) Conert is bestudeer. Beskrywings van die blaaranatomie in dwarssnee en van die abak- siale epidermis word gegee en ge'illustreer deur middet van fotomikrograwe. Die blaaranatomie is tipies van die Danthonieae maar die abaksiale epidermis be- staan hoofsaaklik uit geswolle, seshoekige langselle en huidmondjies en mikrohare is afwesig. Adaksiaal mikrohare is wel waargeneem. Die beskrywing van 'n nuwe genus vir die twee spesies, wat huidiglik in Pseudopentam eris gehuisves word, blyk geregvetdig
te wees maar sekere spesies van P entam eris Beauv. , M erxm uellera Conert en Pentaschistis Stapf toon ooreenkomste met P seudopentam eris en behoort oorweeg te word vir m oontlike insluiting in hierdie genus.
R EFER EN CES
C H IPPIN D A LL, L. K. A ., 1955, In D. M eredith, The grasses and pastures o f South Africa. Johannesburg; CNA. C O N E R T , H. J ., 1971. The genus Danthonia in Africa. Mitt, bot,
S tS a m m l, Munch. 10: 299-308.
D E W ET, J. M. J ., 1954. T he genus Danthonia in grass phyto geny. A m . J. Bot. 41: 204-211.
D E W ET, J. M. J .. 1956. L eaf anatomy and phytogeny in the tribe Danthonieae. A m . J. Bot. 43: 175-182.
D E W ET, J. M. J ., 1960. L eaf anatom y and morphology in South African species o f Danthonia. Bothalia 7: 303-310. ELLIS, R, P., 1976. A procedure for standardizing comparative
leaf anatom y in th e Poaceae. 1. T he leaf blade in transverse section. Bothalia 12: 65-109.
ELLIS, R. P .. 1979. A procedure for standardizing comparative leaf anatom y in the Poaceae. II. T he epidermis as seen in surface view. Bothalia 12: 641-672.
ELLIS, R. P ., 1983. L eaf anatom y o f th e South African D antho nieae (Poaceae), V III. Merxmuellera decora. M. tupulina
and M . rufa. Bothalia 14: 197-203.
