Abstract
Internode growth of vegetative Xanthium plants was studied at various levels on the stem with application of the plastochron index. The bottom internodes were of small size and they displayed small rates of growth. Both, the size of the internodes and their growth rates increased proceeding in the acropetal direction. Rates of cortical cell elongation followed a bell shaped curve, starting with a rate of 7 µm per day, reaching a peak of 15 µm per day and stopping after leaf plastochron index 14. Young internodes, smaller than 25 mm, grew at a constant relative elemental rate of 0.2 day-1 throughout. Internodes larger than 30 mm displayed an acropetal pattern of elongation.
Keywords
Xanthium pensylvanicum; internode; relative elemental rates