|IMPACT OF REPEATED ARTIFICIAL DEFOLIATION AND FLOWERING STALK REMOVAL ON PLANT PERFORMANCE IN LISTERA OVATA
J. H. Willems & M. Leijten
Department of Plant Ecology, Utrecht University
Sorbonnelaan 16, NL - 3508 TB Utrecht, The Netherlands
Herbivory is a very common phenomenon in nature where even the maintenance of entire ecosystems completely depends on grazing animals. However, also small scale herbivory of the green parts of the plants may play an important role in the fate of individuals, since the green leaves are essential for photosynthesis and hence for carbohydrates production and storage in plant tissue.
Selective eating of inflorescences or seed capsules by both small mammals and invertebrates means a direct impact in plant population fitness.
Herbivory can be encountered in a wide variety in terrestrial orchids in Europe among species as well as in individual plants within a population of a given species.
This paper deals with the results of repeated experimental defoliation during two successive years on flowering and seed set of the rhizomatous orchid Listera ovata (L.) Brown. This species is an appropriate model plant with two large leaves each of these can be removed easily without disturbing the plant as a whole. For appropriate experimental interference it is also important that the flowering and non-flowering individuals of Listera ovata can be recorded in a very early stage in aerial life phase. Moreover this species is one of the very few non-threatened orchids in Europe.
Plant performance and flowering ability as a result of flowering stalk removal in an early stage of development will be discussed in relation to carbohydrate content of the underground parts of the plants.
Experimental studies as the one presented may elucidate the impact of herbivory on plant performance and, moreover, contribute to a better knowledge of the life-history strategy of this species in particular and other orchids in general.