Developmental strategies of Koenigia islandica, a high-arctic annual plant

Seed germination, growth and flowering of the arctic-alpine annual Koenigia islandica were studied in controlled environment. Intact (unabraded) seeds germinated poorely at temperatures up to 18°C, with an optimum at 24°C (89% in 10 d). Scarified seeds germinated rapidly, and reached 100% germination in 3 d at 21°C, but no >40% germination occurred at 9 and 12°C, The seeds had no light requirement for germination, nor did fluctuating temperatures improve germination
Dry matter production was optimal at 12°C in both short day (SD) and long day (LD) conditions, but was markedly higher in LD than in SD at identical fluences at all temperatures except 21°C where the plants showed symptoms of severe heat stress. The temperature compensation point for net productivity was estimated to 24°C, and negative carbon balance at higher temperatures might be an important physiological mechanism limiting the distribution of K. islandica in Scandinavia.
Flowering was extremely rapid and independent of daylength, even in a high-arctic population from 79°N, In full summer daylight anthesis was reached 24 d after germination and seeds ripened after 36 d at 15°C, Days to anthesis varied little across the temperature range from 6 to 21°C, giving a linear decrease in the heat-sum requirement for the attainment of flowering with decreasing temperature.
It is concluded that conservative seed germination strategy, tininess and rapid development, low temperature optima for growth and reproduction, and daylength indifference of flowering are important adaptations for success of an annual plant in high-arctic and high-alpine environments, Daylength neutrality has facilitated the wide-latitudinal distribution of K. islandica. including the penetration of the species to the southern hemisphere.