Studies of Growth and Development in the GenusFragaria

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Abstract
It has been demonstrated that photoperiod plays the dominant role in bringing about the reduction in leaf size and in the number of cells in the shortening days of autumn. Strawberry plants in various physiological conditions all respond similarly by prolonging the period of cell division in expanding leaves in response to long-day treatment, and by curtailing the period of cell division in short days. At the lowest temperatures within the normal range for active growth there is a reduction in leaf size and in cell size, and a less marked reduction in cell number. The effect of artificial illumination is shown to depend on the duration of the daily light period, and not on the total daily dose of light Light intensity has no effect on leaf growth over the ranges used, either from fluorescent lamps or from high pressure mercury vapour lamps. The relation between the master reaction determining the cessation of cell division, and that determining the cessation of vacuo-lation is discussed.