BIOSYSTEMATIC STUDIES IN THE LINUM PERENNE GROUP

Abstract

SUMMARYSharp discontinuities in chromosome number and type of breeding system provide more satisfactory characters for classifying the members of the Linum perenne group than most of the morphological characters which have been used in the past. Pollen morphology has great taxonomic value here because it can be used to distinguish diploids from tetraploids and inbreeders from outbreeders. Of seventy European topodemes examined, fifty-seven are diploid [m = 18) and fourteen are tetraploid (2« = 36). The pollen grains of the diploids have three furrows and those of the tetraploids have six pores. All of the European members of the group are heterostylous and self-sterile, except for L. leonii, which is homostylous and self-fertile and endemic to Erance and Western Germany. Artificial hybrids between most of the European members of the group have been produced and their pollen fertilities recorded. No absolute sterility barriers have been found and the whole group is equivalent to a single coenospecies. The course of evolution in the group is considered in the light of all the available evidence.

Pollen-Pistil Interactions

“…Generally unequal style and stamen length distinguish the floral morphs from each other. In addition differences are found in the shape and sculpturing of the exine of the pollen and in the stigmatic papillae, and differences may also occur in wall structure and the type of secretion (OCKENDON 1968, HEITZ et al 1971, DULBERGER 1974. Rejection occurs following self-pollination, but not following inter-morph pollination.…”

The genetics of distyly and homostyly in Turners ulmifolia L. (Turneraceae)

“…Cytological studies indicate that while all tetraploids form quadrivalents, and may be autopolyploids, the three hexaploid varieties form only bivalents at first metaphase, and are therefore likely to be allopolyploids (Shore and Barrett, unpublished data). In other heterostylous families, although there is a tendency for homostyly to occur at higher ploidy levels, no clear pattern emerges (Baker, 1966;Ockendon, 1968;Charlesworth and Charlesworth, 1979b). Dowrick (1956) argued that chromosome doubling may change the position of chiasma formation and result in an increased frequency of recombination within the distyly supergene.…”

Estudios citogenéticos en híbridos triploides y tetraploides de Turnera krapovickasii, T. scabra y T. subulata (Passifloraceae, Turneroideae).

“…Promedio ± ES y variaciones de las asociaciones cromosómicas en MI de los de los híbridos triploides y tetraploides de T. krapovickasii, T. scabra y T. subulata. cuando la planta con el nivel de ploidía más alto es empleada como progenitor femenino, como fuera observado en algunos cruzamientos interploidía involucrando otras especies de Turnera (Shore & Barret, 1985;Arbo & Fernández, 1987, Fernández & Solís Neffa, 2004Fernández et al, 2010) así como especies de otros géneros (Woodell & Valentine, 1961, Ockendon, 1968Levin, 1971). Los resultados obtenidos en este trabajo sugieren que la asimetría en los cruzamientos interploidía podría variar entre las especies de Turnera, ya que aunque en T. scabra los cruzamientos sólo fueron exitosos cuando los tetraploides fueron utilizados como progenitores femeninos, en T. krapovickasii el número de cruzamientos exitosos, así como de frutos y semillas obtenidos, fue variable en las diferentes combinaciones empleadas en los cruzamientos.…”