Insight into “serpentine syndrome” of Albanian, endemic violets (Viola L., Melanium Ging. section) – Looking for unique, adaptive microstructural floral, and embryological characters

Abstract

The genus Viola, particularly Melanium section, rich in metallophytes, is an excellent taxon for study of microevolutionary and adaptation processes. Pollen, ovule, and microstructural floral characters were investigated by LM, SEM, and CLSM in seven endemic Albanian violets, five serpentinophytes (Viola albanica, V. dukadjinica, V. albanica × V. dukadjinica, V. raunsiensis, and V. macedonica), two from chalk soil (V. aetolica and V. schariensis), and in their closest relatives (V. lutea ssp. sudetica, V. tricolor ssp. tricolor, and V. arvensis) for their taxonomic usefulness and adaptive value. Three among analyzed characters were common in all Albanian violets however not unique. Serpentinophytes, V. aetolica and V. schariensis possessed hairs deep inside the spur, developed pollen heteromorphism, both increase the chance of pollination in unpredictable conditions and had strongly developed tannin rich layer in the outer integument of the young ovules with a protective role. They also all exhibited high pollen viability (86.9 ± 10.2%), high frequency of normally developed, enlarged (fertilized) ovules in ovary (65.0 ± 24.0%), but also high frequency of degenerations in developing ovules (40.4 ± 9.8%). Several flower characters may be adaptive in the unfavorable, high altitude environment, including serpentine soils. High pollen viability and normally developed fertilized ovules are sufficient for Albanian species maintenance.

Keywords:

• Stigma and nectary microstructure
• pollen viability and heteromorphism
• tannin layer of ovule
• embryological processes
• pansies

Acknowledgments

The authors gratefully acknowledge the Albanian Ministry of Environment, Forestry, and Water Administration for the official permission to collect plants (No. 7315). We also thank prof. Hermann Bothe from the University of Cologne for help in material collecting, designation, and many valuable comments; prof. John Herr Jr. from the University of South Carolina for critical reading of the manuscript and Mrs. Teresa Stokłosa for technician assistance.