The Control of Runner Development in the Strawberry Fragaria ananassa Duch

Factors controlling runnering of strawberry plants were studiedunder controlled and semi-controlled environments. Increasinglylong exposures to conditions favourable for runnering causeda subsequent increase in number of runners, their total length,number of daughters, and of dry matter produced by mother plants.Leaf and crown numbers of the mother plant showed no such parallelincrease. Temperature supplement to foliage, combined with alight interruption in the dark period, produced the greatestvegetative effect-except again on leaf number-when comparedto either factor individually, normal day extension for threehours by itself or combined with temperature supplement. Itwas suggested that the promotive effects of temperature andphotoperiod on runnering were due to increased activation ofvegetative buds on the rosette crown. Upon comparing constantand diurnally fluctuating temperatures under a constant longphoto-period in the phytotron it was found that, while all othermeasured vegetative criteria were closely similar, the totalrunner length produced by plants under fluctuating temperatureswas almost double that of those under constant temperatures.A temperature gradient from root to shoot stimulated vegetativegrowth in comparison to a gradient in the opposite directionand to lack of such gradient, irrespective of whether the temperaturecommon to both root and shoot was high or low. This was interpretedas resulting from either different temperature requirementsfor aerial and subterranean organs or from the occurrence oftranslocation gradients of substances which promote vegetativedevelopment of the shoots, e.g. kinins and gibberellin-likesubstances. The time interval between rooting of daughter plants and onsetof runnering was increased the later the rooting occurred, possiblydue to the advancing seasonal decline in conditions favourablefor vegetative development. The positional influence of theorder of the daughter along the runner chain, which was markedin flowering, was not found.