The Control of Runner Development in the Strawberry Fragaria ananassa Duch1

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Abstract
Factors controlling runnering of strawberry plants were studied under controlled and semi-controlled environments. Increasingly long exposures to conditions favourable for runnering caused a 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 parallel increase. Temperature supplement to foliage, combined with a light interruption in the dark period, produced the greatest vegetative effect-except again on leaf number-when compared to either factor individually, normal day extension for three hours by itself or combined with temperature supplement. It was suggested that the promotive effects of temperature and photoperiod on runnering were due to increased activation of vegetative buds on the rosette crown. Upon comparing constant and diurnally fluctuating temperatures under a constant long photo-period in the phytotron it was found that, while all other measured vegetative criteria were closely similar, the total runner length produced by plants under fluctuating temperatures was almost double that of those under constant temperatures. A temperature gradient from root to shoot stimulated vegetative growth in comparison to a gradient in the opposite direction and to lack of such gradient, irrespective of whether the temperature common to both root and shoot was high or low. This was interpreted as resulting from either different temperature requirements for aerial and subterranean organs or from the occurrence of translocation gradients of substances which promote vegetative development of the shoots, e.g. kinins and gibberellin-like substances. The time interval between rooting of daughter plants and onset of runnering was increased the later the rooting occurred, possibly due to the advancing seasonal decline in conditions favourable for vegetative development. The positional influence of the order of the daughter along the runner chain, which was marked in flowering, was not found.