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Longitudinal Movement and Loss of Nutrients, Pesticides, and Water in Barley Roots
Authors:SHONE, M. G. T.   WOOD, ANN V.
Abstract:Segments of the roots of young, intact barley plants were treatedin solution culture with labelled nutrients, pesticides, andtritiated water (THO). Some of the labelled substances takenup were lost to the unlabelled solutions surrounding the remainderof the root system. The magnitude of this longitudinal movementand subsequent loss has been compared for phosphate, calcium,and nitrate, for the pesticides simazine and ethirimol, andfor THO. Losses of phosphate and calcium at a distance of 5mm from the treated segments were very small by comparison withthe amounts translocated to the shoots and did not appear tobe greater towards the basal than towards the apical portionof the root system when the labelled solutions were appliedto the middlle segments. There was a larger loss of nitrateand there was some suggestion that this loss was polar, beinggreater in a basipetal direction than towards the root tip.Losses of the two pesticides and in particular of THO were stronglypolar and sufficiently great that over a peried of 24 h onlysmall amounts of these substances which had been taken up bythe apical zones of the roots were translocated to the shoots.The polarity of longitudinal movement and loss of THO was stillvery marked even when transpiration was eliminated by removingthe shoots. Some consideration is given to the possibility ofthe existence of contrasting pathways of movement for the differentsubstances.
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