Australian Weeds June 1982 7

Chromosome number in a Victorian population of repeated several times, adding new stain Amsinckia ca/ycina each time until maximum staining had been achieved on several celJs which were located initially and then examined D. A. Friend periodically. At this stage the coverslip Botany Department. was surrounded by Vaseline and the University of Melbourne, Parkvi lle, Victoria 3052' whole of the material examined thor­ oughly. Photographs of cells at different meiotic stages were taken from this tem­ porary mount. If it was felt that further heating and pressure on the coverslip could enhance spreading of the chro­ Summary species belong) revealed an aneuploid mosomes of a particular cell , the Vase­ series with haploid chromosome num­ line couId be removed from around the bers of n = 8, 12, 13, 15, 17, 18 and Cytological examination of a popula­ coverslip using cotton wool and alcohol 19. Several chromosome numbers were tion of yellow burrweed (Amsinckia and the foregoing procedure repeated. encountered in A . intermedia (n = 15, calycinal from Victoria revealed a Finally, permanent euparol mounts were 17 and 19) and A. menziesii (n = 8, 13 somatic chromosome number of 34 prepared, following the techniques out­ and 17), whereas A . lycopsoides had a (n = 17). T his indicates the close lined by Hair (1968). single haploid number of n = 15. Mem­ relationship between A. calycina, a Twelve such preparations were ob­ bers of the Muricatae were shown to be 'native of South America, and the two tained for examination using material capable of producting hybrids both nat­ Nor th American species Amsinckia ly­ from six plants. copsoides andA. inf£nnedia, which also urally and experimentally. Connor (I %5) OCcur as weeds in Victoria. considered that A . calycina also hybrid­ ized naturally with the two North Ameri­ Results and Discussion can species that are present in Victoria. Chromosome number was determined Introduction in a Victorian population of A. caLycina The population of A. calycina examined as part of an extensive study of the bi­ had a somatic chromosome number of The three species Amsinckia calycina ology and ecology of Amsinckia spp. in 2n = 34 (n = 17). Pollen mother cells (Moris) Chater ( = A. hispida (Ruiz and Victoria (Connor, 1965; Friend, 1977), from which counts were obtained are Pavon) I.M. Johnston), A. /ycopsoides in order to clarify the cytological rela­ shown in Figures I to 3. This chromo­ Lehm. andA. infermedia Fisch. and C.A. tionship between A. calycina and the some number is commOn to the North Meyer occur in Victoria as serious an­ North American species of Amsinckia. American species of the section Muri­ nual weeds, particularly of wheat crops ~atae and indicates the close cytological in the Wimmera and southern Mallee relationship of A. calycina to this group. regions of the State (Connor, 1965; Methods It is possible that the Australian popu­ Willis, 1972; Parsons, 1973). All three lation of A . calycina is represented by several races or fonns having different species are known as yellow burrweed. The material examined was from plants chromosome numbers in a manner sim­ Amsinckia Lycopsoides and A . inler­ grown from seed collected from Beulah ilar to that described for A. menziesii and media are nalives of North America (Ray in north-western Victoria (latitude A. infermedia by Ray and Chisaki (1957b, and Chisaki, 1957a; Munz, 1959) and 35°56'S, longitude 142°25'E). Single 1957c), and a full examination of the have been examined cytologically by Ray anthers were removed from flowers taken Australian material needs to be under­ and Chisaki (1957a, 1957b, 1957c) in from the terminal portion of infloresc­ taken in order to determine whether this a taxonomic study of the North American ences and examined by squashing in is so. Indeed, the wholeoftheAmsinckia species ofAm sine kia. A . calycilla. which aceto-carmine to determine the state of complex in Australia requires cytologi­ is the most widespread species in Vic­ meiosis of the pollen mother cells. The cal investigation to provide further in­ toria (Connor, 1965) is a native of South remaining anthers of flowers found to formation on the relationship between America (MacBride, 1960; Chater, be at a suitable stage were then put into 1971), and was not included in Ray and a stain-fixer consisting of 3: I glacial the Australian and the American species. Chisalei's study. Morphologically A . ca­ aceto-carmine to which had been added Ray and Chisaki (l957a, 1957b, lycina is most closely related to the North either ferric acetate or ferric chloride 1957c) discuss their studies on Am­ American species A. menziesii (Mac­ saturated in glacial acetic acid. Staining sinckia from the viewpoint of the evo­ Bride, 1960; Connor, 1965), which was of the chromosome improved over a lution of a colonizing species. Based on examined by Ray and Chisaki. Both are period of up to four days in the stain­ characters including nutlet morphology, characterized by a small flower size, with fixer. Squashes of the anthers were pre­ flower size, stamen insertion and style the coroll a 2 to 3 mm broad and 4 to pared using aceto-cannine to which a length, they link the North American 6 mm long inA. menziesii and 2 t04 mm solution of 4% iron alum had been added species in an evolutionary sequence from broad and 5 to 8 mm long inA. calycina. at the rate of a few drops per 100 mL. the large-flowered heterostylic species A. lycopsoides and A . intermedia have After squashing and removing all debris to the small-flowered homostylic species. larger flowers, being up to 8 mm broad with fine forceps, the size of the drop Cytologically the evolutionary sequence and 15 mm long. All species are hom­ of stain was adjusted to the size of the was shown to be from low chromosome ostylic, and the small flower size ensures coverslip, which was then applied. numbers (n = 4 to 7) in the heterostylic self-pollination through actual contact Spreading of the chromosomes was species to high chromosome numbers between the stigma and the anthers at the achieved by gentle heat applied to the (n = 8 to 19) in the homostylic species. time of poUen release. slide followed by firm pressure on the Cytological examination by Ray and coverslip, which was held at the same Chisaki (1957c) of members of the sec­ time under absorbent paper to prevent tion Muricatae (to which all the Victorian · Presenl address: Tasmanian Depan men t or Agri culture , lateral movement. These procedures were South Launceston . Tas mania 7250 . 8 Australian Weeds June 1982

The secti on Muricatae contains species was provided by th e Wheat In dustry Journal of Botany 6:277--84 . with homostyli c fl owers and the majorit y Research Committee of Victoria . with MacB ri de, J. F. ( 1960). Flora of Pem. Bot­ of the small nowered, self- pollinated additional financial support from a Uni ­ ani cal Series 13 Pan 5 No.2. Pub!. No. species with hi gh chromosome numbers, vers it y of Me lbo urne Researc h 902. Field Museum of Nat ural History , and would therefore appear to be the Scholarship. Chicago. p. 596. Mun z, P. A. ( 1959). A Californiafl Flora. most advanced. The advantages of sel f­ Univers ity of California . Berk eley, pollinati on to a colonizing species in References Californi a . allowing for a rapi d increase in popu­ Parsons, W. T. ( 1973). Noxious Weeds of lation from an ini tially present fe w or ViCforia . (nkata Press, Melbourne, p. 29. ev en one individual have been recog­ Allard, R . W. ( 1965) . Genetic systems Ray, P. M. and Chisaki , H. F. (1957a). ni zed for a long time (Stebbins, 1950), associatcd with coloni zing ability in pre­ Studies on Amsinckia. I. A synopsis of the whilst a hi gh chromosome num ber con­ domin antly self-poll inated species. In The genus. with a study of heterostyly in it. fers a hi gher genetic recombinati on on Genetics of Colonizing Species (eds H. G. American Journal of BOlallY 44:529-36. the occasional cross-pollinations that do Baker and G. L. Stebbins) . Academic Ray , P. M. and Chi,aki , H. F. ( 1957b). occur (Allard, 1965). It is quite stri king Press. New York. pp. 49-75. Studies o n Amsinckia . II . Relati onship Dlater. A. o. ( 197 1). Amsinckia Lehm. Bot­ among the primitive species. AmeriCllll th at it is to the section Muricatae that anical Jourl/al of fh e Limwell Society of Journal of Botany 44 :537-44. most of the weedy members of the genus Londoll 64 :380. Ray , P. M. and Chi ,aki, H. F. ( 1957c) . Amsinckia belong. Connor. D. 1. (1965). Eco logical studies on Studies on Amsinckia. ill. Aneuploid div­ the genus Amsillckia Lehm. in Victoria. ersification in the Mu ricatac . American Ph .D. thesis, University of Me lbourne. Joun/al oj Botany 44:545- 54 . Friend , D. A. (1977). The ecology of Am­ Stebbin s, G . L. ( 1950). Variafion alld Ev­ Acknowledgements sinckia (Amsinckia spp .) in wheat crops olution i" Pla nts. Columbi a Uni versity in Vi ctori a. Ph .D. thesis, University of Press, New York, p. 176. Me lbourne. Will is. 1. H. ( 1972). A Handbook to Pla"ts This work form ed part ofa Ph .D. project Hair, J. B. (1968). The chromosomes of the ill Victoria. Vol . II . Dicotyledons. Mel­ carried out in the Botany Department of Cupressaceae. I. Tetraclineae and Acti­ bourne U niversity Press, Melbourne. the Uni versity of Melbo urne. Funding nostrobeae (Call it roideae) . New Zealand p. 535.

...... ~ ..--- r.., . '-..., .. .'-, :-,..., . ,

• • .. , , • • • • .- .. .. Iff ~ , .. •r -.- .' if t • • • ,, '" " .. , • -• Figure 1 metaphase I (X 6140) Figure 2 metaphase II (X6140) Figure 3 anaphase II (X4650)

Figures 1 to 3 Meiosis In pollen mother cells of Am­ smckla calycin a : haploid chromo­ some number. n = '7.