The transfer of plants to boron-free solutions induces rapid responses in membrane functions without necessarily affecting root growth and anatomy. In sunflowers (Helianthus annuus), root growth slows within 3-6 h. However in maize (Zea mays), no growth effects are apparent after more than 30 h without boron (-B). In both species early disturbances in ion uptake and cell wall deposition are seen. Ultrastructural studies on sunflower root tips after 5.5 h or 3 d -B are reported. Detailed studies on the absorption of P<sub>j</sub> and K<sup>+</sup> by root tips were complemented by studies on protoplasts isolated from the root tips of +B and -B plants. There were no significant differences in the protoplast yield or viability according to their B status. Ion absorption by protoplasts isolated from roots of +B and -B plants generally resembled that by intact roots of the corresponding B status. Altering the B status of the protoplasts was expected to initiate earlier responses than in the roots where cell wall binding and diffusion times buffer the system against change; but the greater variability inherent in measuring the protoplast responses prevented the detection of subtle changes. The activities of two+ membrane bound arjzymes were investigated; β-glucan synthetase and a K<sup>+</sup>-stimulated, Mg<sup>2+</sup> -dependent ATPase. UDPG incorporation by protoplasts continued for over 18 h and was consistently higher in +B protoplasts and root membranes than -B. However SEM revealed no significant differences in fibre deposition around sunflower and maize protoplasts according to their boron status. (K<sup>+</sup>+Mg<sup>2+</sup>)-ATPase from sunflower roots was found to be reversibly impaired by the loss of B; and preliminary investigations implied that restoration of activity when B was resupplied to the intact roots was correlated with the B content of the membrane fraction, as determined by the (n,α) method.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:351440 |
| Date | January 1984 |
| Creators | Heyes, J. A. |
| Contributors | Loughman, B. C. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:6ce60488-a5b0-4ba0-94ea-d59ee8622596 |
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