LINEAR AGGREGATIONS OF STOMATA AND EPIDERMAL-CELLS IN TRADESCANTIA LEAVES - EVIDENCE FOR THEIR GROUP PATTERNING AS A FUNCTION OF THE CELL-CYCLE

We tested Charlton's hypothesis (1990) that stomata are present and pa tterned in linear cell aggregations using the monocot Tradescantia. We examined the following features of the leaf epidermis in support of t his theory: linear groups (strings) of stomatal complexes and of epide rmal cells were sought in immature and mature regions of entire leaves ; the lengths (in cell number) and incidences (numerical occurrence) o f both string types were determined; the uniformity and progression of stomatal differentiation within strings were studied; physical charac teristics of differentiating strings within cell files were measured. Undifferentiated epidermal cells from the leaf base were stained with DAPI to reveal precursors of stomatal strings immediately proximal to the stomatal initial region. The results indicated that the Tradescant ia epidermis in the leaf blade consists of linear groups of stomata an d epidermal cells, which did not change in cell number nor incidence d uring development. The incidence of stomata by length was nonrandom. A lthough incidence decreased with string length, the decline was not li near nor exponential. Stomatal strings show cell cycle synchrony in DA PI staining of stomatal precursors and synchrony of stomatal different iation within a string. The irregularity in the length of the stomatal development region, and each differentiation stage in it, by cell fil e was consistent with the variation in string length and unity in stri ng development. The evidence supports Charlton's hypothesis that cells are patterned based on their position in the cell cycle and that line ar groups of stomata reflect cell lineages, which maintain a degree of cell cycle synchrony. (C) 1995 Academic Press, Inc.