Le cycle de développement végétatif, en conditions naturelles, de l'Helianthus scaberrimusEll.

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Abstract
The developmental cycle of H. scaberrimus can be divided into a few main phases. The subterranean stolons show moderate activity from Oct.-Feb. of the following year. The most intense period of lengthwise growth is that of the aerial parts from April-July. An increase in thickness of the underground stem appears in June; it occurs along with considerable stolon production. These neostolons undergo quite active lengthwise growth in June, July and Aug. They tuberize and simultaneously produce roots in Sept. and Oct. All of this morphogenesis corresponds to a cessation of aerial growth. The morphological type of tuberized stolon is completed as soon as the end of Oct. This stolon is now characterized by clear correlations between its thickening process and its root formation. These correlations and the amount of thickening and root-formation condition the intensity of the subsequent plant growth. A gradient of morphological strength of the stolon is defined and a method to select the stolons for sampling is devised.