Pollen morphology and localization of Ni in some Ni-hyperaccumulator taxa of Alyssum L. (Brassicaceae)

Abstract

Pollen morphology of seven Alyssum L. taxa growing on serpentine soils in different places in the European Mediterranean macrobioclimate territory were studied, described and compared. Cluster analysis was performed to show similarity between species and their populations. The shape of the pollen grains varies among the species and among the grains within the same anther. The pollen grains are 3-colpate, prolate, with long and narrow colpi reaching the poles. The ornamentation of the exine varies from micro-reticulate to reticulate between the species. Pollen sterility/fertility was also calculated. The highest percentage of sterile pollen (73.76%) was calculated for Alyssum murale subsp. murale and the lowest (9.54%) for A. bertolonii subsp. bertolonii. All species are representatives of sect. Odontarrhena (C.A. Meyer) Koch well known as Ni-hyperaccumulators. Nickel and other elements present in pollen and stamen were studied by inductively coupled plasma-mass spectrometry. The stamen parts of all species were micromorphologically analyzed by scanning electron microscopy coupled to an energy-dispersive X-ray probe. Accumulation of Ni was detected in the stamens of all studied species and rarely in the pollen grains. The distribution patterns of Ni were similar among the species examined.

Keywords:

• Nickel
• Mediterranean
• serpentine
• stamen
• sterile pollen

Acknowledgements

The authors are thankful to Prof. Eleni Eleftheriadou from Greece and Prof. Aida Bani from Albania for kindly providing material for this study. An anonymous reviewer presented critical comments on the manuscript.

Supplemental data

Supplemental data for this article can be accessed at 10.1080/11263504.2014.989284.

Additional information

Funding

The research was realized within Project TK-02/39 supported by the National Research Council at the Ministry of Education and Science in Sofia, Bulgaria.