Effects of Water Deficit on Leaf Development in Tobacco

Abstract

Leaf initiation, leaf area, and the numbers and areas of palisade cells in developing leaves at five nodes were followed during a period in which tobacco plants were deprived of water. The rate of leaf initiation in well-watered plants was constant with time, but was rapidly reduced by a small water deficit and ceased at leaf water potentials of less than - 750 J kg-1. Cell expansion showed a similar response to water shortage, but cell division was much less sensitive, continuing although at a reduced rate even after leaf expansion had ceased. The expansion of a leaf on a well-watered plant could be described by a simple logistic relation with time from unfolding. The course of cell number and size during expansion could be accounted for by assuming that cells always divided at the same size, that the proportion of cells passing into a further cycle of division decreased as a negative logistic of time and that all cells expanded in the same manner, i.e, over 4 days at a rate which fell linearly with time.