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Morphological and biochemical variations in St. John’s wort, Hypericum perforatum L., growing over altitudinal and UV-B radiation gradients

MARIJA ROBLEK ; Dept. of Biology; Biotechnical faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia
MATEJA GERM ; National Institute of Biology, Večna pot 111, 1000 Ljubljana, Slovenia
TADEJA TROŠT SEDEJ ; Dept. of Biology, Biotechnical faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia
ALENKA GABERŠČIK ; Dept. of Biology, Biotechnical faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia

Sažetak

Abstract

Background and Purpose: The climate of the Alpine region is marked by a higher proportion of UV radiation which, combinedwith other stresses, plays an important role in determining the differences between highland and lowland plant populations. The study was aimed at identifying the plant habitus as well as selected morphological and biochemical properties that enable optimised growth under given conditions, and at determining the potential of plants to cope with UV-B radiation stress.

Material and Method: St. John’s wort, Hypericum perforatum L., thrives in a continuum of habitats from lowlands to highlands. Chlorophylls a and b and UV absorbing compounds (AC) were determined. The height of the plants, internodes and shoots, and the angle of the shoots were measured. Thicknesses of epidermis, palisade and spongy tissues were examined and evaluated by the computer program AnalySIS 3.0 (Soft Imaging System, Münster, Germany). The number of seeds was counted and their weight determined at the end of the growing season.

Results and Conclusions: The content of total UV absorbing compounds (AC) in leaves increased with altitude. The average content of total UV AC in plants growing at 1300 m a.s.l. was about 25% higher than at 400 m a.s.l... The content of chlorophyll showed the opposite trend. At high altitudes plants were shorter, due to shorter and reduced numbers of internodes. Reproductive success was much lower in plants growing at high altitudes; they developed fewer flowers (on average 147 at 400 m a.s.l. and 50 at 1700 m a.s.l.) and seeds per plant than those growing in lowlands. The present study indicates that St. John’s wort growing at high altitudes has developed an effective strategy to mitigate the effects of the severe alpine climate.

Ključne riječi

altitude gradient; chlorophyll; plant architecture; reproduction; UV absorbing compounds

Hrčak ID:

32576

URI

https://hrcak.srce.hr/32576

Datum izdavanja:

31.10.2008.

Posjeta: 1.732 *