ABSTRACT
This chapter presents a result from studies conducted at the University of Tromso. In these studies, both the climatic regulation of growth and the development of cold hardiness in herbaceous grass species, cloudberry and woody Salix plants have been investigated. Environmental control of growth and development in northern grass species has been reviewed by O. M. Heide. Both the growth habit and the total dry matter production of northern grass species are affected by temperature and photoperiod. There are no exact and generally accepted definitions for the northern areas, but they will include the Arctic, the Subarctic, and at least parts of the boreal zone. The Arctic can be considered to cover areas north of the tree line, and the Subarctic to consist of areas between the tree species line and the economic tree line. Plant species growing in the Arctic and Subarctic are adapted to complete their annual growth cycle during a short and cold summer season.
