Resumen de Cytogenetics, Geographical Distribution, Pollen Stainability and Fecundity of Santolina impressa (Asteraceae: Anthemideae)
Santolina impressa (2n = 2x = 18) is an endemic species of Portugal, with restricted geographical distribution. The present study aimed to explore its chromosomal variation in respect to chromosome morphology, meiotic behaviour, and effects on pollen stainability and fecundity. Its karyotype formula was found to be either 12m + 2msat + 2smsat + 2st (75% of the individuals) or 12m + 2msat + 3sm + 1smsat (25% of the individuals). Univalents were observed in 29.21% of the meiocytes. Chromosome fragments due to breakage in the chromosome arm were observed in 10 meiocytes only (11.23% of the meiocytes). Chains and rings of trivalents were observed in 14.60% of the meiocytes (one trivalent per meiocyte was observed). Chains and rings of quadrivalents were observed in 21.34% and 11.23% of the meiocytes, respectively, with a range of 0�1 per cell. Nine plants (40.90% of the total) with 2n = 2x = 18 + 2B showed a quadrivalent configuration in diakinesis. Twenty abnormal anaphases with delayed disjunction of the four non-homologous and the two homologous chromosomes were observed. Simple chromosome bridges without fragments and interchromosomal adhesions were observed in 35.95% of the anaphases analyzed. B chromosomes showed bivalent association in diakinesis and their segregation at anaphase I was normal. Pollen was found to be fertile (mean ± s.d. = 89.57 ± 47.14%); the effect of univalent frequency and frequency of abnormal anaphase I on pollen stainability was strong and statistically significant.
