Showing papers by "Bedford College published in 1949"

Photoperiodic Control of Leaf Growth and Cambial Activity in Pinus sylvestris

Abstract: IT has long been known1 that geographical races of Pinus sylvestris from northern latitudes show reduced growth of the shoot when planted in more southern localities. Sylven2 and Langlet3 suggested that this is probably a photoperiodic effect, arising from differences in the natural length of day between different localities. My experiments have shown that Pinus sylvestris is indeed photoperiodic. As in many other species4, short photoperiods (10 hr.) induce earlier cessation of growth of the shoot in first-year seedlings of P. sylvestris as compared with long photoperiods (15 hr.), so that fewer leaves are formed before the formation of a terminal resting-bud. There is also a reduction in the length of the 'internodes', leading to a rosette type of growth, under short days.