Komatsu, Akiko

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RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:Ecological Studies of Stellariamedia and S. neglectaKomatsu, AkikoKomatsu, Akiko. Ecological Studies of Stellaria media and S. neglecta. Memoirs of theFaculty of Science, Kyoto University. Series of biology. New series 1970, 3: 13-211970-03-31http://hdl.handle.net/2433/258794MEMOIRS OF THEFAcuLTy     Vol.oF SclEncE, KyOTO ILTNIvERSITy, SERIEs oF BIoLoGy III, pp. 13-21, March 1970Ecological Studies of Stellaria mediaand S. neglecta*      ByAkiko KoMATsuLaboratory for PIant Ecological Studies, Faculty of Science,Kyoto University(Receivecl December 27, 1969)   ABSTRACT Ecological differences between Stellaria f7tedia and S. neglecta, beingclosely related with each other, were studied.   Their habitats and lives for each season were investigated in the field. Labora-tory experiments were made on germination of seeds, photosynthetic rate and chloro-phyll content.   Habitat investigation showed that S. medi- is dominant in cultivated fields, whileS. negleeta scarcely occurs there. This may be ascribable to the difference ofphysiological nature between the two species. S. media has the characteristicsadapted to life in cultivated fields, that is, shoyt after-ripening, germinating severaltirnes in a year and early attaining to the reproductive phase. Rare presence of S.neglecta in cultivated field is mainly due to its longer vegetative growth period.                               Introduction     Stellaria media and S. neglecta are annual or biennial weeds, which dis-tribute all over the world. They liave many similarities in the external inor-pliology and the mode of life. In the papers concerning the chick weeds,therefore, strict distinction between S. media and S. neglecta was not made sofarE))2),3), And in their. taxonoixLy they are classified as a species4), two variantsbelonging to a species5), or different species6),7}.    PetersonS}, who regarded them as different species, referred three closelyrelated species (S. o2eglecta, S. media and S. aPetala) to media-group. -einvestigated the media-group from the view points of cytology, genetics, ecologyand systematics. But ecologically he discussed' only about the ecotype as to thegermination of S. media.    This paper will deal with conditions of habitats and physiological character-istics of S. media and S. neglecta. And ecblogical differences between them* Contribution No. 8 from the Laboratory for Plant Ecological Studies.  14 Akiko KoMATsuwill be explained.                         Materials aRd Metheds    The field investigation was carried out mainly in Kyoto City and its environs.In the experimental researches S. media was collected from the farm of KyotoUniversity and S. neglecta from the attached Botanical Garden.    Table 1 shows ordinary taxonomic criteria to identify these two species.            Table 1. ComparisGn of criteria between the two specieg....... .. . ..-..stemleafstamenseedwhole sizeS. media S. neg'lecta./.Ilbrownsmaller2-5 ( -8)l. O-1. 2processsmaller& deeper greenmm acrossheinispherical'I"I pale green, seldom brownlarger & paler green(3-) 8-101.5 mm acrossprocess conical, subacutelarger    In these characteristics only the shape of processes on the surface of seedis the most stable for environmental changes. Although individuals bearingintermediate process form are rarely found, it is not so difficult to identify themjudging from other features (stamen number; color, forrn or size of the leaf,etc.) and mode of life.. + . . .             Vegetative stage rlovvering stagt FrusC::fgceatiOn  Cotyledon                R:I.I NI.4 R-- l•5'v2 R>2           Fig. 1. Developmental stages and leaf forms of S. neglec;a.                              R--1.-e-nt.g7dgehh    As shown in Fig. 1, S. neglecta alters the leaf form transitionally fromseedling to fructification stage. In S. media, however, it was observed toflower bearing the young leaf form (R==1. 1) and no definite relationship betweenthe leaf form and the developmental stage was revealed.    Their habitats were investigated at 77 places in the suburbs of Kyoto latein autumn, 1966. In this time S. media had already flowered and the leavesof S. neglecta were young form yet, which made it easy to distinguish them.In each investigated area (2-10m2) coverage of S. media and S. neglecta, andEcological Studies of Stellaria media. and S. neglecta l5the conditions of environrnent were reeorded.    In order to examine the most suitable germination temperature and the criticalone, the seeds were set under the following temperatures: 50, 100, 150, 200, 2seand 300 (Å}le, respectively). In the experiments to examine the effect of hightemperature treatment on the after-ripening o'f seeds, they wei-e laid under' 350expediently for six days, and then incubated under 140, optimal germinationtemperature, with control seeds having been kept in room temperature (180Å}20).eeQeo"oooeeo"k'Aaooeo ooooeoooo                Fig. 2. Assirnilation chamber (upper view).    The plants used for the measurement of photosynthesis and chlorophyllcontent were grown outdoors for 40 days in four experimental plots under 119oi,47.0oi, 88.0of and 100.0o/ relative light intensities, respectively. Then 17-28 leaveswere harvested from each plot, set in an assimilation chamber (Fig. 2), andphotosyntlietic rates were measured with infra-red gas analyser (URAS) at 200and at a flow rate of 30 l/hour. Chlorophyll was extracted from the leaves with80.0of acetone and the total chlorophy]1 content (mg!100cm2 leaf area) was deter-mined spectrophotometrically by the method of Arnon9).                                Results                         l. Field investigations1) Habitat    The investigated habitats may be classified into five categories, namely, toe  80- soaa 4o:2   Side ef Bank Shade of     ditch treesFig. 3. Dominance-Presence Index (DPI)        measured at different habitats in        S. media; hatched, S. neglecta.Waysideof S. "radia and S.Nov. -Dec., 1966.Cultivated fieldneglectaBlank.16 Akiko KoMATsvside of ditch, banl<, shade of trees, wayside and cultivated field. Dominance-Presence indicesiOi of both species were computecl for each habitat category (Fig.3). Both species are found with nearly equal DPI in the first four categories.In the last one, ho"iever, there.•is a prominent difference in their dominancy,S. media being superior to S. neglecta.2) Liecycle    As shown in Fig. 4, in Kyoto S. neglecta usually gerininates in the termextending over Septeniber and October, 'flowers from Marc'h to April next year=.9v'es'o=z--es Eo- Lav Åëee-o aÅë .E'v= Le- Åë•-ut )-oo--tu-c.9-" vaso=.-Les EÅë--Laev eÅëE an.co ev'-o"eL-looaL-`.                   J F M A M j j A S O N D                                  Month       Fig. 4. Diagram showing germination and flowering Period (Kyoto).and dies late in lvl.fty. The majority of S. media seecls germinate in autuinn,but they often germinate also from spring to early summer. The floweringperiod of S. media is not so restricted as that of S. neglecta, and uncler tlienatural condition, S. media begins to flower at about a month after germinatlon,continuing to produce seeds for two to three months.3) Cold resistance    It was observed that in winter the leaf spongy tissue of tliese species issplit, makingalarge space of intercellular cavity (Fig. 5,A). But in thesespecies growing in spring or autumn, or in a greenhouse even in winter, nosuch phenomenon was observed (Fig. 5,B).    HatakeyamaM has already explcainecl the same phenomenon as an adaptationEcological Studies of Stellaria media and S. neglecta 17./;•esut•re  ,,.}pe:trk.t l.                                            'kbl-CS!,-E•          Fig. 5. Cross sections of S. 7nedia leaves in winter; (A) a leat                  in the field, (B) a leaf in the greenhouse.to freezing in frozen Buxus leaves, That is, as the air temperature goes down,ice pieces grow larger in the intercellular space of the spongy tissue taking theintracellular water. In consequence the resistance against freezing of the cellcontent increases and the intracellular space is not frozen. In fact it was observedthat in early morning when the air temperature strikingly dropped leaves of S.media in the field were frozen, but that as the air ternperature rose the icepieces were thawed and they did not suffer any damage.10080g:i,g'20o'i  t 2. Experiments        /ON       -S    /K  O-?,,t{  /ex,L/,,e N,.                Is Xe                :                 :                 :                 IB                  ,AFig.     5 10 t5 20 25 30               Temperature ( "c )6. Correlation between germination and temperature.   A, S. fn.edia; B, S.neglecta.  18 Akiko KoMATsu1) Germination and after-riPening    The optimum temperature for germination of. these species was 15e, or so,and the lower limit was 50. Seeds of S. media, however, germinated 'upto 300,while those of S. neglecta did not above 200 (Fig. 6).    As for the seeds of S. neglecta treated with high temperature it took 14days to attain 60/0oi germination, but the control seeds 30 days (Fig. 7). For100se6:20o''/   /'?' ' " .f'.//.et v t'         t--"-.de A     .Ze!        et      tt    e.   x. '  ' t'        --      e.     '    '   '   ' t- , ''det.•. B               6 8 10 12 14 16 l8 2e 22 24 26 28 3e                                Days            Fig. 7. Germination of S. neglecta seeds treated with high                   temperature (350). A, treated; B, control.S. media, on the other hand, both treated and untreated seeds collected from theplants grown under 250-270 in the laboratory germinated 100.0o- during 5 days,but the seeds collected in the field early in December required about a monthunder the room temperature for completion of after-ripening.2) Photosptnthesis and chloroPhyll content    Any appreciable difference was not observed between the two species ofeach experimental plot in either compensation point or light saturation point (Fig.8). In any light condition, however, the photosynthetic efficiency of S. mediawas higher than that of S, neglecta.    The chlorophyll content of S. media was higher thcan that of S. neglectain any experimental plot. And the differences of thickness of their leaves weresmall, so S. media contains more chlorophyll in a unit volume of the leaf thanS. neglecta (Fig. 9).                        Discussion and Conclusion    S. media ancl S. neglecta are nearly related with each other phytotaxonomi-Ecological Studies of Stellaria media and 6. neglecta 19leii'io-2lei,a,e-2    .IT.1Ll        •.i.ii[Iite----. -..o-"--e.----      ttel."-.- e        e-ete"-     e/ ,/ ...e."'O" "Q""e---.o/oi.t' Ot 88 01ot  /./.". . .ti-    e-e-eNeze/ ..ee.----e-..---. .e  ..Q' o•tt470/.    te 2e       Klux8. Light-photosynthesis   grown at varioust    l:.,oZle,Fig.    /" e e /e e  ..O"."e--.....q-...                   --eQ'tt           soo o!.l-/ig'o: o1 3i.g'gmm1oe1x9.giFeChlorophyll contentleaf) and leaf thicknessferent light conditions:47!0o!(B), 889oi(C) andrelative light intensities.S. "vadia; hatched, S.       3e                    to 2o 3e                       K[ux       curves of S. media and S. neglecta    relative light intensities indicated. O, S. meaia; O-----O, S.neglecta.               cally and have the same life-form.               Although they have many similari-               ties in their physiological charac-               teristics, there are some clifferences               responsible for the ecological dif-               ferences between them.                   S. media seeds"produced under               low temperatures require after-               ripening foT a month or so, and               while tlaose under high temperatures               do not. It is, therefore, tlaottght               that the temperature condition dur-               ing the seed production is an impor-               tant factor for the after-ripening of               S. media seeds. And it may be      D suggested that S. media seeds are               matured on the mother plants when               the air temperature is favorable for(mgllOOcm2               proceeding seed ripening.    at dif-   11.o.i(A), MOSt of S+ neglecta seeds  loo.o.i(D) require after-ripening for about a    Blank, month, and it is distinct from Fig. neglecta. 7 tlaat the after-ripening is promoted  20 Akiko KoMATsuby higher temperatures.     About the after-ripening of seeds collected from many countries in the world,PetersonS} has classified S. media into the following three ecotypes : 1) almostnever need it, 2) require its period for 40 to 50 days, 3) longer than type 2).    iMore detailed investigations will be shortly conducted to decide if the after-ripening of S. media and S. ne.crlecta is genetic, as Peterson reported, or variableby the temperature condition during the seed production.    The physiological differences between the two species are as follows. Thedifference in the flowering period is very important. The flowering period ofS. media having short vegetative growth period is not so restricted as that of S.neglecla, being longer than the latter. It may imply that the seed output ofS. media is large in comparison with S. neglecta.    Since S. media seeds germinate at 50-30e, they can germinate almost all theyear round in Japan. When S. neglecta seeds produced in spring are after-ripened, the air temperature has already become too high to germinate becausethey can germinate only at 5e-200. In 1967, late in May when the air temperaturedropped unusually many seed]ings of S. neglecta were found. llowever, becauseof high temperature and drying in summer they died without flowering. Likethis the seedlings of S. neglecta are sometimes found in spring but they scarcelyflower.    The photosynthetic efficiency of S. media is hjgher than that of S. neglectaahd this may be due to chlorophyll content. As for compensation point andlight saturation point, no difference is detected between the two species. Thedominancy of S. media in photosynthetic efficiency may contribute to its rapidgrowth. .    Usually the plant known as weed of cultivated fields has the followingcharacteristics: to have short after-ripening period, to germinate through theyear and to have precocious ' tendency. Of course, these characteristics are welladapted to life in farm lands being often weeded and culeivated. Evidently S.media has these characteristics as farm weeds. S.neglecta is disadvantageousto grow in such a place because of a longer vegetative growth period. This isalso showed by the investigation of habitat (Fig. 3). And generally both S.media and S. neglecta are almost absent in mountains but, so far as the author'sobservat'ion concerned, even there (e.g. Mt. Hiei, Mt. Ohdaigahara) at the culti-vated fields and at the surroundings of houses S. media is often found with otherweeds. Thus ecologically it is the most important difference that S. media isa weed of cultiva'ted fields and S. neglecta not so, and it may be said that theformer is more advantageous than 'the latter concerning distribution. AccordingtoHitzer,3) S. media occurs all over the world, because the climate factor restrict-ing its distribution is drying only. ' But he did not discussed about the relationbetween the farm weed characteristics and distribction,                             Acknowledgement    The author wishes to express her deep thanks to Prof. I. I-Iatakeyama, Assist.              Ecological Studies of Stellaria media and S. neglecta 21Prof. S, Kuroiwa, Dr. H. Tsuji and Dr. H. Tabata of the laboratory for their valuablecriticisms and advices.   She is also indebted to Dr. T. Suganuma of Nara Women's University for hishelpful advices in the field survey.                                References 1) Matzke, E. B. 1932 Flower variations and symmetry patterns in Stellaria    media, and their underlying significancel Amer. Jour. Bot., 19: 477-507 2) Matzke, E. B. 1930 Der Einfluss einiger Bedingungen, besondersderBuntblEit-    trigkeit, auf die Zahl der Staubblatter bei Stellaria media. Planta, 9: 776-791 3) }E[itzer, K. 1935 Die Bedingungen der BIUtenbildung von Stellaria media. Flora,    29: 309-335 4) Makino, T. 1966 Makino's New Illustrated Flora of Japan, Hokuryukan,    Tokyo. 5) Mizushima, M. 1965 A conspectus of the genus Steleart'a in .Iapan I. Journ.    Jap. Bot., 40 90-96 6) Ohwi, J. 1965 Flora of Japan, Shibundo, Tokyo. 7) Kitamura, S. & G. Murata 1961 Coloured Illustrations of Herbaceous Plants    of Japan II, Hoikusha, Osaka. 8) Peterson, D. 1936 Stellaria-Studien. Bot. Not.:281-419,9) Arnon, D. 1946 Copper enzymes in isolated chloroplasts. Plant Physiol., 24:    1-1510) Suganumq, T. 1967 Phytosociological studies on the semi-natural grassland    used for grazing in Japan II. Bot. Mag, 80: 145-16011) Hatakeyama, I. & J. Kato 1965 Studies on the water relation of Buxtts leaves.    Planta, 65: 259-268

Ecological Studies of Stellaria media and S. neglecta

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Ecological Studies of Stellaria media and S. neglecta

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