ALLEVIATION OF AL-TOXICITY IN WHEAT BY BORON 1. ANATOMICAL AND ULTRASTRUCTURE EFFECTS OF ALUMINIUM ON ROOT OF ALUMINIUM-TOLERANT CULTIVAR OF TRITICUM AESTIVUM

摘要

The effect of aluminium was investigated on the seedlings pre-treated by two concentrations of boron 4 muM or 32 muM grown in water culture using a concentration of 500 muM A1 for 3 days. Semithin and ultrathin sections of the apical region of the roots and transmission electron microscopy micrographs were analysed of fourteen-day-old Al-tolerant ('Sakha 93') cultivar of Triticum aestivum. Results showed that the amelioration effect of boron treatment was pronounced at 32 muM B level. Rigidity of cell wall and plasma membrane in the wheat root apex cells (Zone of root hairs) could result from the formation of bonds of ions of the toxicant with components within their structures and appears as dark precipitants in cross sections. Cross sections of the apical region of the control plant roots showed well-developed normal anatomical structure and cell ultrastructure typical for those of root regions. Slight alterations under the influence of aluminium or boron alone or both of them and the role exhibited by boron in ameliorating of aluminium toxicity were observed. In spite of these alterations, the seedlings keep grown in face of Al-stress. The obtained results proved the high resistance of the studied 'Sakha 93' cultivar to aluminium stress. Aluminium detoxification coincides with increased Ca~(2+) content in the root apex to cope with alleviation of Al-stress; boron may have a role in this concern. Possible Al-toxicity and -tolerance, as well as boron alleviation of toxicant stress in this tolerant cultivar was briefly discussed.