title: Responses of meristematic callus cells of two Cynodon dactylon genotypes to aluminium.
abstract: Responses to Al3+ of embryogenic callus cells of an Al-sensitive (Al-S) and Al-resistant (Al-R) Cynodon dactylon genotype were evaluated with regard to Al3+ toxicity and resistance. A chemical equilibrium speciation model (MINTEQA2) was used to ensure the availability of the Al3+ ion in culture media, which was supplied as 0.08-2.3 mM Al3+ for 2-8 weeks. Increasing Al3+ concentration and exposure time had a greater negative impact on the Al-S than on the Al-R genotype, in terms of callus growth rate and frequency of non-embryogenic cells. Exposure to 0.8 mM Al3+ for 2 weeks resulted in an 88% reduction in the Al-S meristematic cell number, whereas that of the Al-R genotype remained unaffected. In addition, the Al-S cells accumulated three times more Al in the nucleus than did the Al-R cells, suggesting that Al interfered with mitosis. The Al-R cells appeared to exclude Al3+ from its cells through an increase in extracellular pH (4.34 in Al-R and 4.08 in Al-S) and by the immobilisation of Al in the cell wall (33% more in Al-R). The results showed that by studying the cellular responses to Al3+ it is possible to discriminate between the Al-S and Al-R C. dactylon genotypes.
authors.affiliation: School of Life and Environmental Sciences, George Campbell Building, University of KwaZulu-Natal, Durban 4041, South Africa. ramgareebs@ukzn.ac.za
authors.forename: Sumita
authors.initials: S
authors.lastname: Ramgareeb
authors.forename: John A
authors.initials: JA
authors.lastname: Cooke
authors.forename: M Paula
authors.initials: MP
authors.lastname: Watt
mesh_terms: D000535:Aluminum / Q000378:metabolism / Q000633:toxicity*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019343:Citric Acid / Q000378:metabolism; D031744:Cynodon / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D005838:Genotype; D006863:Hydrogen-Ion Concentration; D018519:Meristem / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D019343:Citric Acid; D000535:Aluminum