Studies in Dormancy of Sycamore: II. THE EFFECT OF DAYLENGTH ON THE NATURAL GROWTH-INHIBITOR CONTENT OF THE SHOOT

1. An investigation was made into effect of daylength conditionsof the inhibition content of first-year seedlings of sycamore(Acer pseudoplatanus). 2. The shoot apical regions and mature leaves were extractedwith 80 per cent. Aqueous methanol, fractionated by paper chromatographyin isopropanol/ammonia and assayed by the wheat-coleptile growthtest. 3. A growth inhibitor was present in all extracts at R_f 0.7.Higher levels of inhibitor were present in both apices and matureleaves of plants transferred to short-day conditions than ofthose maintained under long-days throughout. 4. These difference in inhibitor level can be detected after2–5 days of short-day treatment, Preceding any markedeffect of daylength on growth. 5. Evidence is adduced in support of the hypothesis that theinhibitors is produced in the leaves during darkness and istransported to the apex during the photoperiod.