The timing of that transition, and not differential growth, is the major determinant of ultimate epidermal cell size. At the same time the cell cycle duration in the cortex gradually decreases and cells divide at a smaller size. Whether this is related to the decrease in epidermal cell proliferation and, as a result, the increased availability of a potential cell proliferation factor is an interesting question. By the end of Stage II stomata differentiation is completed. Intriguingly, the end of this stage coincides with differentiation and expansion of cortex cells, and it occurs closely after the appearance of medial vascular bundles, the final step of vasculature formation in the pedicel. These observations suggest a temporal coordination of differentiation in 4-(Benzyloxy)phenol different tissue layers during Stage II. Considering that so many changes are occurring in the epidermis and cortex during this stage, it is remarkable that the overall exponential rate of pedicel growth in Stage II is similar to the rate during Stage I. This is somewhat surprising, as the epidermis is believed to control organ growth and one might expect that multiple differentiation events in the epidermis would have an impact on the overall rate of growth. Instead, our observations are consistent with the mechanism determining the rate of organ growth being unaffected by cell differentiation in the epidermis. Stage III is a cell elongation stage and lasts for,100 hours. Very little if any cell proliferation occurs during this stage in either the epidermis or the cortex. Overall pedicel growth during this stage transitions from exponential to linear, it is not uniform along the proximodistal axis, and it depends on flower fertilization occurring just before Stage III starts. It would be most logical to compare the dynamics of pedicel growth to growth of stems, but a detailed 
temporal analysis of stem growth is lacking. The mechanistic basis of leaf growth, however, has been studied extensively. After initiation, two stages of leaf growth are described. Epidermal and mesophyll cells initially proliferate, and then epidermal cells switch to expansion, starting at the distal end of the leaf and progressing towards the proximal end. This transition to cell expansion occurs abruptly in a specified leaf region simultaneously with the differentiation of chloroplasts and onset of photosynthesis, leading to the hypothesis that retrograde transport from chloroplasts regulates the transition to cell expansion in the epidermis. Just as in the cortex of the pedicels, the transition to cell expansion is significantly delayed in the mesophyll compared to the epidermis. Since most chloroplast differentiation and photosynthesis occurs in the mesophyll, it is somewhat surprising that a retrograde signal would induce epidermal but not mesophyll cell expansion. Stomata differentiation precedes pavement cell expansion by approximately one day, and Tulathromycin B continues until the leaf reaches its mature size. For the most part, the leaf growth pattern closely resembles the pattern of pedicel growth. In both cases growth begins with a cell proliferation stage, followed by a period in which stomata differentiate and pavement cells elongate, and ending with a period of mesophyll expansion. In both organs the differentiation of stomata slightly precedes elongation of pavement cells, and the transition to stomata differentiation occurs around day 9�C10. Despite the similarities, there are several differences between leaf and pedicel growth. The stomata differentiation period is significantly prolonged in leaves, and the onset of mesophyll expansion does not coincide with the termination of stomata differentiation. The extended stomata formation period is likely necessary for the establishment of a higher stomatal density in leaves compared to pedicels.