Influence of long photoperiods on the growth of timothy (Phleum pratense L.) varieties from different latitudes in northern Europe

Abstract

AbstractPlants of three varieties of Phleum pratense L. from different latitudes (cv. Engmo, 69°N; cv. S48, 52°N; cv. Motim, 52°N) were grown from the five‐leaf stage at 12°C under continuous illumination or 8‐h days at essentially identical daily inputs of radiant energy. The responses to daylength extension (increase in plant dry weight, plant height and leaf dimensions and reduction in the number of tillers per plant and in tissue dry matter content) were common to all three varieties and although the enhancement in plant dry weight and in leaf size was greater in the Engmo plants, this was principally the result of poorer growth and smaller leaf size in 8‐h days. Marked differences between Engmo and the other varieties in the partitioning of dry matter within the plant were the consequence of differences in the rate of reproductive development. For example, compared with S48 and Motim, first spike emergence and 50% anthesis in the Engmo plants were delayed by 22 and 14 days, respectively, and 40% of the Engmo plants did not become reproductive even after 110 days of long‐day treatment. Furthermore, by the time that 50% anthesis of the mainstem spike had been reached by the long‐day plants of each variety, significant differences in tiller numbers and tiller fertility had developed between the varieties from high and lower latitudes. These findings and the results of previous studies of Poa pratensis, Dactylis glomerata and Bromus inermis are discussed in relation to the adaptation of high‐latitude grasses to the Scandinavian environment.