Ecological studies of lettuce (I)

Development of the floral organ

Abstract

Premature bolting is one of the most serious problems in head lettuce culture. In the course of ecologiol studies of head lettuce, observation on the developmental process of flower clusters and flowers was carried out in relation to bolting.
After a slight elongation of the stem, the growth point of the stern thickened and rounded up, then its base was surrounded by bracts. This stage was designated as “terminal cluster differentiation stage”.
Then lateral clusters differentiated in the axils of bracts succesively from top to base of the stem (“lateral cluster differentiation stage”).
Bracts developed around the base of the terminal cluster (“bract formation stage of the terminal cluster”), then primordia of flowers started to develop inside of the bracts (“flower primordia formation stage”).
Petals, stamens, carpel, and pappus in the order were formed successively in each flower (“petal”, “stamen”, “carpel” and “pappus formtion stages”).
These developmental stages were illustrated in the figures 1_??_13.