DIFFERENTIATION IN LEAF EPIDERMIS OF CHLOROPHYTUM-COMOSUM BAKER

The distribution of guard mother-cell formation has been studied in developing abaxial epidermis in the basal meristem of the leaf of Chlorophytum comosum. It is concluded that, as tissue is displaced from the base of the leaf by growth, it passes through a proliferative zone in which only proliferative mitoses occur, and then passes a boundary into a formative zone in which formative mitoses occur, giving rise to guard mother cells, and proliferative mitoses are absent. Further distally, formative mitoses die out and in the next zone (the guard-cell zone) the only mitoses which occur are those by which the guard mother cells give rise to the guard cells. Most distally there is a zone with no mitotic activity. The probability of a cell undergoing a formative mitosis is highest at the proximal boundary of the formative zone. It is consequently suggested that the fate of a cell on entering the formative zone depends partly on its position in the mitotic cycle; cells nearest to mitosis at entry are the most likely to undergo a formative mitosis during their passage through the formative zone. Similarly, guard mother cells which fail to undergo mitosis may be those which were most distant from mitosis on entry into the guard cell zone. These suggestions may explain some of the elements of pattern previously found in the mature epidermis. © 1990 Annals of Botany Company.