Fjölrit RALA - 15.02.1995, Side 6

4
SUMMARY
Biological studies ofNootka lupine (Lupinus nootkatensis) in Iceland.
Growth, ejfect of cutting, seed set and chemical composition.
Results of biological studies on the introduced Nootka lupine (Lupinus nootkatensis
Donn ex Sims) are presented. The studies started in 1987 and were mostly carried out
at sites in the south-western part of Iceland. The main objective of the work was to
obtain a basic knowledge of the species for more effective utilisation in land
reclamation, forestry and agriculture. The following subjects were investigated:
growth and maturity of the lupine during the growing season and with age, responds
to cutting at different times, self-fertilisation and seed set, and the chemical
composition of the plant.
The Nootka lupine is a perennial which spreads by self-seeding. In the first
season the plants form only one stem and reach a height of about 10 cm. In the third
season the plants have 3-5 stems and are about 60 cm high. At this age they usually
bloom and produce seeds for the first time, which they do annually thereafter. The
plants grow in number of stems and general size for a number of years. The largest
plants encountered have 100-110 stems and are considered to be about 10 years old.
Individual Nootka lupine plants can probably reach an age of over 20 years. The life
span of the species is relatively long in comparison to other lupine species. The
Nootka lupine has a rapid growth rate in the spring. It starts flowering in early June
and the first seeds are ripe in the beginning of August. Growth of the lupine
continues until first frosts in the autumn. Under favourable conditions the plants may
reach a height of over 120 cm. Lupine patches can give a high dry-matter yield,
comparable to high yielding, fertilised hay-fields. In the autumn about 65% of the
lupine consists of stems, 30% of leaves and 5% of seed-pods. Annual allocation
towards reproduction is relatively low in the Nootka lupine. It has a large storage
root, the root/shoot ratio being slightly higher than 1 at peak shoot biomass in the
autumn. An average Nootka lupine plant with about 30 stems has a 3-4 kg total fresh
weight of shoots and root in the autumn.
Lupine plants regenerated after cutting in early summer and autumn. They
were, however, very sensitive to cutting from the middle of June towards the end of
July, when root store is limited. Most of the plants cut during that period were killed.
The lupine is, on the other hand, able to regenerate from seed bank and gain its former
abundance in a few years if competition from other species does not prevent seedling
establishment.
The adult plants studied had 25 flowering stems on the average. Each
inflorescence had 65 flowers of which 17 developed into seed pods. About 5 seeds
matured in each pod. Thus, the plants produced about 2100 seeds on the average.
Seed production was higher in plants growing at the fringe of a lupine patch than
inside it. Covering of flowers to hinder insect pollination did not prevent seed
development. Self-fertilization in the Nootka lupine appears to be in the range of
70%. Humble bees are probably the only insects in Iceland capable of cross-
fertilising the lupine.
The Nootka lupine has a very high crude protein content, it is abundant in
minerals and the fibre content is not high in comparison to most other fodder plants.
However, alkaloid content prevents its use for grazing or as fodder. Sheep feeding on
Nootka lupine in grazing experiments in Iceland have developed lupine poisoning.
Sparteine appears to be the dominant alkaloid in the lupine. The alkaloid content of
the Nootka lupine seems to be relatively low for a wild lupine species. A
considerable difference was found in chemical composition of shaot parts. The leaves
contained far more protein, less fibre and more alkaloids than the stems. The limited
chemical analysis carried out on the roots gave similar ranges for most substances as
in the shoots, except for alkaloids which were considerably less in the roots.