Croissance des coenocytes provasculaires dans la racine de Marsilea diffusa (Marsiléales)

Abstract

Five types of provascular strands of coenocytes with 2, 4, 8, 16 or 32 nuclei have been recognized in the central region of the root apex of Marsilea diffusa Lepr. This observation is relevant to studies of cellular differentiation and to the pattern of root growth and can be summarized as follows. (i) Nuclear division in the coenocytes of each strand is well synchronized. (ii) The other phases of the nuclear cycle show less synchronization. (iii) The levels of deoxyribonucleic acid (DNA) vary between 2C and 4C and endomitosis does not occur. (iv) Nuclear division is followed by a final S phase. (v) Correlations exist between (a) the content of DNA and the volume of the nucleus and (b) the volume of the coenocytes and the volume of their nuclei. (vi) The nuclear cycles of the coenocytes in the same provascular strand are of similar lengths. (vii) The growth of the coenocytes follows a standard allometric curve: their volume is doubled with each nuclear cycle. (viii) During each nuclear cycle, the central region of the root apex grows at the rate of 62%.