Effects of Daylength on Cell Length and Cell Number in Strawberry Petioles

Abstract

Effects of photoperiod on the length and number of epidermal cells in ‘Donner’ strawberry petioles were investigated.
The number of cells in petioles which were differentiated under natural daylength between May and June increased as the leaves emerged and petioles elongated later in 16-hr daylength (LD); concurrently, the average cell length became shorter. The mean cell length also decreased when leaves emerged under 9-hr daylength (SD); the numbers of cells per petiole of the first three petioles to elongate under SD conditions were not significantly different.
Petioles which differentiated and elongated under SD had shorter cell length and fewer number of cells compared to those growing under LD. Petiole cell length was controlled by photoperiod after emergence of the petioles, whereas cell number per petiole was independent of daylength.
The leaf emergence interval (days per leaf) was longer for leaves which differentiated under SD than that which differentiated under LD. As petiole length decreased, the formation of runners (stolons) was inhibited.
Cell division in leaf initials enclosed in the plant crown is inhibited by SD. This responce will be one of the reasons why petioles become short under LD at high temperatures at the beginning of the rest period.