| Popis: |
Pollen of tea ( Camellia sinensis L.) was germinated in liquid culture and the rate of extension growth of the pollen tube was used to study the effect of the acidic polypeptides poly-L-aspartic acid and poly-L-glutamic acid on the toxic effects of Al on tip growth. Tube extension was inhibited as much as 70% by 10 gmM Al over 20 h of growth. Citric acid at a molar ratio of 3:1 was able to reduce the inhibition to 40%. However, poly-aspartate was much more effective, being able to reduce inhibition to about 50% at a ratio of 1:1 (20 μM poly-L-aspartate:20 μM Al, the poly-aspartate molarity being calculated using the molecular weight of the individual aspartate residue). Growth could be completely protected from toxic effects of Al at a ratio of 10:1. Similar results were found with the same concentrations of poly-L-glutamate. The polypeptides alone had no effect on growth. It is probable that the polypeptides bind Al. Since a requirement for Ca 2+ , and the involvement of calmodulin, are implicated in pollen tube growth, the polypeptides may prevent Al from interfering with Ca 2+ transport, or from binding to calmodulin. |
