Life History of Peltandra virginica Author(s): Benjamin Goldberg Source: Botanical Gazette, Vol. 102, No. 4 (Jun., 1941), pp. 641-662 Published by: The University of Chicago Press Stable URL: http://www.jstor.org/stable/2471954 . Accessed: 11/08/2011 10:15 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to Botanical Gazette. http://www.jstor.org VOLUME 102 NUMBER 4 THE BOTANICAL GAZETTE June 1941 LIFE HISTORY OF PELTANDRA VIRGINICA BENJAMIN GOLDBERG (WITH FORTY-NINE FIGURES) Introduction A morphologicalstudy of Peltandravirginica Kunth was made to assemble data which would give a rathercomplete life history of a widespreadplant and a basis forcomparison within and outside the Araceae. Features neglectedor incomplete- ly ascertainedin theplant and the familyas a wholewere studied as fullyas possi- ble. Comparativestudies on the aroids (13, 23) have been of interestsince ENGLER (IO, i i, i2) pointedout that in spite of appreciable variationthere were unifying tendenciesin the group. The only detailed morphologicalaccount of Peltandra(7) deals with part of the developmentof the pollen. Additional reportsinclude a microchemicalstudy of the seed and its germination(i8), a demonstrationthat the seed can germinatein almost total absence of oxygen(8), and an account of seed frequencies(9). Observations Peltandrais foundthroughout the easternUnited States and has been reported west of the MississippiRiver. It is an inhabitantof freshwater marshes, especial- ly along the banks of tidal rivers. The stem is a subterraneanvertical rhizome (figs.I, 2R), cylindrical,and with a diameterin mature,unbranched specimens of 8 cm. The leaves are so compactlyarranged that internodesappear nonexistent. The rhizomesometimes branches (fig. 2B) and the branches become separated fromthe parent plant as thebasal portionof the rhizomedecays. Since branchesas well as parentaxis formerect rhizomes, there results characteristically a clusterof plants. Some rhizomesbear ioo or more adventive roots, which reach a diameterof 641 642 BOTANICAL GAZETTE [JUNE about 7 mm. in theirproximal portions. Roots arise acropetallyon the rhizome (fig.i) and sometimespierce the sheathingleaf bases. Wrinklingof the outercorti- cal tissuesof rootsof seedlingsand older plants occurs,sometimes contracting to almost 50 per cent of the originallength in some regions. 4 -AR L~~~ co 'A JP FIGS. i-8.-Fig. i, plant collectedin October. Fig. 2, branchedplant in dormantstate with roots removed.Fig. 3, longisectionof germinatingseed (CO, cotyledon;L, lumen of haustorialcell). Fig. 4, seedlingi6 days old with cotyledon(CO) still withinpericarp. Figs. 5, 6, transverseand longisections throughapex of maturerhizome. Figs. 7, 8, longisectionsof younginflorescences. Above the concave top of the rhizomeduring most of the year is a large conical terminalbud (fig.i TB) about I 5 cm. long, extendingfrom the top of the rhizome to the soil surface. From thisbud, containingrudiments I5 cm. to 50 y long,only a part of the outer,older, and largerrudiments emerge in late spring;the remain- ing ones, excludingthose which abort duringthe interim,emerge during the fol- I94I] GOLDBERG-PELTANDRA 643 lowingyear. The various regionsof the leaf are clearlydefined. Leaves of mature formand size have a sheath 4.5-6.5 dm. long (includingthe subterraneanportion extendingfrom the soil surfaceto the apex of the rhizome),a stalk 2-4 dm. long, and a sagittateto hastate lamina reachingat timesa lengthof 5 dm. (fromthe acu- minate apex to the roundedbasal lobes) and a widthof 2 dm. The largerinflorescences are about 70 cm. long,from the subterraneanproximal region of attachmentof the peduncle to the distal end of the spathe. The dark green spathe is 20-30 cm. long and extendsa fewcentimeters beyond the inclosed spadix. While thereis much variation,most plants in Maryland are at the height of theirvegetative and floweringactivity by the end of May or early June. After pollination,which occurs at this time,the distal part of the spadix, covered with staminate flowers,disintegrates, together with the distal part of the spathe, marked offby a slightinvagination. The erect inflorescencesbend below the at- tachmentof the spathe to the peduncle,the fruitingspadix finallypointing toward or restingon the soil. The fruits,surrounded by the enlargedbasal part of the spathe, ripenin Augustor September. SEED AND SEEDLING The dark greento brownobovoid fruitsmeasure about I.5 cm. long and i cm. wide, and showan apical scar markingthe formerposition of the style. Withinthe membranouspericarp lies usually one, but sometimesas many as three,seeds im- bedded in a colorlessjelly-like material. To the conspicuous,flattened-globular, micropylar portion of the seed is at- tached an obovoid chalazal appendage about 2-2.5 mm. long, which marks the position of the large haustorial cell of the endosperm. Within the seed lies the large embryonicsporophyte enveloped by the residualendosperm and the almost entirelywithered parent sporophytictissue. The layer of remainingendosperm surroundingthe embryois one cell thick,except in the regionnearest the empty haustorialcell, where it is about seven cells thick. The integumentshave become brownishand shriveled,but the parent sporophytictissue in the chalazal region formsa thickcoat aroundthe emptyhaustorial cell. The pale greencotyledon forms the greaterpart of the embryo,and has almost the same size and shape as the more conspicuousmicropylar portion of the seed. In a deep grooveof the cotyledonnear the apex of the seed lies the narrowlyconi- cal, greenplumule, about 9 mm. long and 3.5 mm. in diameterat its base. It con- tains six or seven foliarstructures. Since it is partlyencircled by the upgrowthof cotyledonarytissue, it formswith the cotyledona compactbody. The radicledoes not forma groupof tissues topographicallydelimited from the surfaceof the rest of the embryo. Occasionallythe hypocotyledonaryportion of the radicle appears on the side of the cotyledonas a poorly definedswelling, I.5 mm. thick and 4-5 644 BOTANICAL GAZETTE [JUNE mm. wide. About I.5 mm. below the base of the plumule on its exposed side lies the primaryroot, a slight rounded protuberanceless than i mm. in diameter. Around the primaryroot the surfaceof the hypocotylis marked by three to five small, circular,partially hyaline areas which indicate the position of adventive root primordia. Usually the seeds germinatein April,but in some cases they germinatein the late summerof the year the ovules werefertilized, and while the fruitsare still at- tached to the parent plant. By the time germinationoccurs the ovary wall is usuallyso decayed that it presentsno mechanicalobstacle to germination.As the plumulerises fromits cotyledonarygroove (fig.3PL), the membranousenvelope (E), consistingof the remains of endospermand integuments,is ruptured. Al- thoughthe primaryroot generallyfails to elongate,it may attain a lengthof 2.5 cm. beforewithering. The adventive roots (fig.3AR) grow and elongate rapidly; the firstones are small and short-lived,those formedlater approach by degreesthe maturesize. Figure 4 shows a seedling,with a few adventiveroots (AR) and the firstthree cauline foliar structures,i6 days aftergermination began. The first emergencewas a bladeless sheathlikestructure about 2 cm. long, the second and thirdpossessed elliptical laminae, and the thirdalone a distinctstalk below the lamina. The primaryaxis increases rapidly in diameter,so that the young rhi- zomes show an obconical tapering. MATURE PLANT BRANCHING.-The seedling behaves as a monopodiumuntil initiationof the firstinflorescence, which is developed directlyfrom the apex of the primaryaxis. Apical growthis thencarried on by a bud whichdevelops in the axil of the penulti- mate leaf. In the axil of the ultimateleaf a second bud is formed,which gives rise only to a basal acroscopic,two-keeled prophyll and a second inflorescenceat its apex. The bud in the axil of the penultimateleaf completelydisplaces the original apex of the shoot in prominenceand central position, so that outwardly the branchingsystem appears unchanged,and the branch developing fromthis bud also ceases its apical growthwith the formationof an inflorescence,after it has given rise to its share of leaves. Apical growthof the plant is then maintainedby a bud in the axil of the penultimateleaf of the branch. The process is continued; and thougha matureplant has an erectvertical rhizome, it is actually composedof superposed branches of increasinglyhigher rank. ENGLER (io), recognizingthe sympodial nature of the shoot in practicallyall the Araceae, regardedthe shoot correspondingto the one arisingfrom the bud in the axil of the penultimateleaf of the Peltandrashoot as a unit in the structureof the plant and called it a Fort- set'ungspross(continuation shoot). As in the primaryaxis of the seedling,a second inflorescence(fig. sB), together witha two-keeledprophyll (P), is bornein the axil of the ultimateleaf (U) of each I94I] GOLDBERG-PELTANDRA 645 continuationshoot.