Full text in pdf format

Reproductive morphology, genetic control and incompatibility relations in tristylous Oxalis physocalyx(Oxalidaceae)

Rosilux Paques de Barros Pacheco; James R. Coleman

Departamento de Botânica, Instituto de Biociências, Letras e Ciências Exatas, UNESP, 15100 São José do Rio Preto, SP, Brasil

ABSTRACT

Oxalis physocalyx Zucc. ex Progel is shown to be tristylous. Pollen production was determined to be greatest in the short anther whorls, intermediate in the mid anther whorls and lowest in the long anther whorls. Pollen size is dimorphic, the lower anther whorl of each morph producing pollen grains 30 pm in diameter and the upper whorl 40 /.lm in diameter. The genetic control of style form is by two unlinked loci, one controlling short versus non-short, the other mid versus long. Short is epistatic to non-short, and mid is dominant to long. Legitimate pollinations were more successful than illegitimate, both in frequency and seed production per capsule. However, illegitimate other form crosses were successful when longs and mids were used as females, as were self and own-form crosses of longs. Despite these modifications of incompatibility relations, representation of style morphs in natural populations indicates isoplethy. It is suggested that isoplethy results from a competitive advantage of legitimate over illegitimate pollen when pollination is mixed and that incompatibility relations in O. physocalyx are essentially unmodified functionally.

Keywords: reproductive; morphology; genetic; control; incompatibility; relations; tristylous; Oxalis physocalyx.

REFERENCES

Bennett, J.H., Leach, C.R. and Goodwins, I.R. (1986). The inheritance of style length in Oxalis rosea. Heredity 56: 393-396.

Darwin, C. (1877). The different forms of flowers on plants of the same species. John Murray, London.

Eiten, G. (1963). Taxonomy and regional variation of Oxalis section Corniculatae. I. Introduction, keys and synopsis of the species. Amer. Midl. Natur. 69: 257-309.

Finney, D.J. (1952). The equilibrium of a self-incompatible polymorphic species. Genetica 26: 33-64.

Fisher, R.A. and Mather, K. (1943). The inheritance of style lengths in Lythrum salicaria. Ann. of Eugenics 12: 1-23.

Fyfe, V.C. (1950). The genetics of tristyly in Oxalis valdiviensis. Heredyty 4: 365-371.

Fyfe, V.C. (1956). Two modes of inheritance of the short-styled form in the genus Oxalis. Nature 11 7: 942-943.

Ganders, F.R. (1979). The biology of heterostyly. NZ. J. Bot. 17: 607-635.

Lourteig, A. (1975). Oxalidaceae extra-austroamericanae. I. Oxalis L. sectio Thamnoxys Planchon. Phytol. 29: 449-471.

Mulcahy, D.I. (1964). The reproductive biology of Oxalis priceae. Amer. J. Bot. 51: 1045-1050.

Ornduff, R. (1964). The breeding system of Oxalis suksdorfii. Amer. J. Bot. 51: 307-314.

Ornduff, R. (1972). The breakdown of trimorphic incompatibility in Oxalis section Corniculatae. Evolution 26:52-65.

Ornduff, R. (1983). Heteromorphic compatibility in Oxalis nelsonii. Bull. Torrey Bot. Club 110: 214-216.

Ornduff, R. (1987). Reproductive systems and chromosome races of Oxalis pes-caprae. L. and their bearing on the genesis of a noxious weed. Ann. Missouri Bot. Gard. 74: 78-84.

Progel, A. (1877). Oxalidaceae. In: Flora Brasiliensis (Martius, C.F.P. von and Eichler, A.G. eds). Typographia regia, Minachii 12:474-520.

Richards, A.J. (1986). Plant Breeding Systems. George Allen and Unwin, London.

Spieth, P.T. (1971). A necessary condition for equilibrium in systems exhibiting self-incompatible mating. Theoretical Population Biology 2:404-418.

Von Ubisch, G. (1921). Zur Genetic der trimorphen Heterostylie sowie einige Bemerkungen zur dimorphen Heterostylie. Biol. Zentralbl. 41 : 88-96.

Von Ubisch, G. (1926). Koppelung von Farbe and Heterostylie bei Oxalis rosea. Biol. Zentralbl. 46:633-645.

Weller, S.G. (1975). The evolution of distyly from tristyly in the North American species of Oxalis section Ionaxalis. Evolution 30: 442-454.

Weller, S.G. (1976a). Breeding system polymorphism in a heterostylous species. Evolution 30: 442-454.

Weller, S.G. (1976b). The genetic control of tristyly in Oxalis section Ionoxalis. Heredity 37: 387-392.

Weller, S.G. (1978). Dispersal patterns and the evolution of distyly in Oxalis alpina. Systematic Botany 3: 115-126.

Weller, S.G. (1979). Variation in heterostylous reproductive systems among populations of Oxalis alpina in southeastern Arizona. Systematic Botany 4: 57-71.

Weller, S.G. (1980). The incompatibility relationships of tristylous species of Oxalis section Ionoxalis in southern Mexico. Can. J. Bot. 58: 1908-1911.

Weller, S.G. (1981). Fecundity in population of Oxalis alpina in southeastern Arizona. Evolution 35 : 197-200.

Weller, S.G. and Ornduff, R. (1977). Cryptic self-incompatibility in Amsinckia grandiflora. Evolution 31:47-51.