Distribution within the plant or compartmentation does not contribute substantially to the detoxification of excess boron in sunflower (Helianthus annuus )
Frank Dannel, Heidrun Pfeffer and Volker Römheld
Australian Journal of Plant Physiology
26(2) 95 - 99
Published: 1999
Abstract
Distribution and compartmentation of boron as possible mechanisms for the notable tolerance of sunflower (Helianthus annuus L.) to excess B supply have been studied. Following a short- term treatment (6 h) with 1000 µМ B, the distribution of B between different shoot organs was preferentially directed to the readily transpiring ones. Thus, B distribution in sunflower plants seems to be mainly influenced by transpiration and does not act as a B tolerance mechanism in sunflower. As a second possible mechanism for B tolerance, the compartmentation of B between water insoluble residue (i.e. cell wall) and cell sap (i.e. symplasm) was determined. Additional binding of B in the cell wall in response to excess B supply for 6 h was very low in leaves and negligible in roots. Thus, a substantial contribution of the cell wall in detoxification of excess B can be ruled out. In an additional experiment with a B supply of 1 µМ (marginal) to 1000 µМ (moderately toxic), the compartmentation of B between the apoplasmic fluid and the cell sap was investigated. The B concentration in the apoplasmic fluid was always lower than that in the symplasm. Thus, B was not excluded from the symplasm, but accumulated within it. The apoplasmic fluid did not contribute substantially to the detoxification of excess B in the leaf.Keywords: boron, compartmentation, detoxification,
https://doi.org/10.1071/PP98110
© CSIRO 1999