CONICET | Buscador de Institutos y Recursos Humanos

Abstract: Echium plantagineum (Boraginaceae) is native of the Mediterraneanregions, has been introduced and become widespread within the American continent(North to South), South Africa, New Zealand and Australia. This plant hasseed dormancy, aggressively spreads to infest vast areas of predominantly agriculturalland and is considered a toxic weed to livestock. The objectives of thisresearch were: (i) to study the morpho-anatomy of the diaspores of E. plantagineum;(ii) to identify the pathway of water uptake; and (iii) to characterize the germinationand the seedling. The morpho-anatomical studies were carried outanalyzing semi-permanent slides of transverse and longitudinal sections of thefruits, seeds and seedlings. Histological, histochemical and conventional stainingtechniques by using stereoscopic, optical and scanning electron microscopy wereapplied. In the diaspores, the water uptake pathway was determined by fast greenstaining, germination tests were performed and the morpho-anatomy of seedlingswas analyzed. The diaspores showed acrescent calyx surrounding the fruit, composedby 4 rough tuberculate mericarpids. Each indehiscent mericarpid enclosesan exalbuminous seed with a thin coat and a spatulate embryo with folded cotyledons.Water uptake took place through the vascular trace ?protuberance? in thecicatrix of the mericarpid, which triggers the germination process. Germinationwas epigeal, the cotyledons were photosynthetically active at the emergence,and a rudimentary developed gemmula was observed. Germination percentagewas 66.5%. The macrosclereids of the pericarp functions as an obstacle to wateruptake, which is overcome when the mericarpid is detached from the gynobase,and the protuberance that acts as a water uptake path is exposed, leading to germination.The morpho-anatomical characteristics of diaspore, explain the successfuldispersal for this aggressive weed, and provide important information inrelation to the necessary care for its control.