42:	Epidermal cell growth in leek leaves (Allium ampeloprasum L. var. porrum).

Authors:	Matitschka, Gudrun(A)Nelson, C., Jerry.(B)
Affiliations:	(A): Department of Fruit Science, Vegetable Science, and Viticulture, University Hohenheim, Stuttgart Germany (B): Department of Agronomy, University of Missouri, Columbia, MO
Presenter:	Matitschka, Gudrun , agrojhc@showme.missouri.edu

Leek (Allium ampeloprasum L. var. porrum) is a monocotyl vegetable plant with a simple morphological structure. Usually no flowering or tillering occurs during plant production. Therefore, leek is a model plant to study leaf growth that is undisturbed by simultaneous or interuptive growth of other shoot organs. Three growth chamber experiments were conducted during 1998 with potted plants. Two experiments compared light effects (300 and 500 mmol m-2s-1 PPFD) at 18 C. The third experiment compared temperature effects (11, 18, and 25 C) at 500 mmol m-2s-1 PPFD. Cell lengths in the abaxial epidermis were measured by image analysis on leaves which were growing at a constant leaf elongation rate until harvest. A region of 1-2 cm above leaf base contains small undifferentiated cells that are about 40-60 mm long, i.e. the cell production zone. From 2-20 cm above leaf insertion epidermal cell length increases up to 500-700 mm. Therefore, cell elongation zone and maximum cell length are much longer in leek than in tall fescue (Festuca arundinacea Schreb.) where the cell division zone is about 0.3 cm long, the epidermal cell elongation zone is 2.5-3.5 cm long and maximum cell length is about 350-400 mm. The relation between cell length and distance above leaf insertion can be described by a Feldmann-function. In leek 95 % of the estimated maximum cell length is reached about 17 to 20 cm above leaf insertion. Cell length continued to increase slowly (1 mm mm-1) even at 25 cm the last measurement position. Leek epidermal cells needed 15-30 days to reach final cell length. This contrasts with the 3-4 days required for tall fescue epidermal cells. The time needed for the elongation of one cell was also affected by temperature (60, 20, and 25 days at 11, 18 and 25 C respectively).