Calcium amelioration of aluminium toxicity effects on root hair development in soybean [Glycine max (L.) Merr.]

Abstract

SUMMARYLow activities of the monomeric aluminium (Al) species, AP+, AKOH)^" and A1(OH)2+ in solution reduce root growth and root hair development in soybean [Glycine max (L.) Merr.]. Calcium (Ca) ameliorates to a certain extent the toxic effects of Al on root growth, but the interactive effects of Ca and Al on root hair development are not known. In the absence of added Al in solution culture, Ca concentration over the range 500-2000 //M had little effect on root growth or root hair development of soybean cv. Fitzroy. Where the sum of the activities of the monomeric Al species was 2 //M, taproot elongation and lateral root development of soybean was suppressed in solution with 500 //M Ca. The length of the root hair zone was only 10% of that in plants not exposed to Al, and scanning electron microscopy revealed a low density of root hairs. Increasing the Ca concentration to 2000 fiM largely overcame these deleterious effects. The results are discussed in relation to the role of root hairs as infection sites for Bradyrhizobium, and the known effects of Al in suppressing nodulation in soybean.

Toxic effects of Pb2+ on the growth and mineral nutrition of signal grass (Brachiaria decumbens) and Rhodes grass (Chloris gayana)

“…However, care must be taken when interpreting the results of Lane and Martin (1980), because the high P concentration used (2 mM) has been shown to -Page 14 -influence root hair growth (Foehse and Jungk 1983). The apparent lack of detrimental Pb 2+ effects on root hair growth is also in contrast to those observed for Al toxicity (Brady et al 1993;HechtBuchholz et al 1990) and Cu toxicity (Kopittke et al 2007b;Kopittke and Menzies 2006) in which root hair formation is reduced at lower metal concentrations than those required to reduce root elongation. In the present study, root hairs developed within 1 mm of the root tip (Figure 2i,k) indicating that cells close to the root tip were not killed by Pb 2+ but that there was a severe disruption of normal root development in which root hairs develop distal to the elongation zone.…”

Tip growth patterns and growth rates of root hairs on ‘Tamar’ white clover(Trifolium repensL.) in low ionic strength culture solution

“…In lily pollen tubes grown in vitro, tip Ca 2+ and elongation rate oscillate regularly with large amplitudes (Messerli et al 2000). Growing root hairs have a high calcium gradient at the tip (Schiefelbein et al 1992) and calcium is essential for root hair growth in soybean (Brady et al 1993). This suggests that calcium-regulated pulsatile growth may be a general feature of extension growth of root hairs.…”

“…There are no obvious reasons why white clover root hair growth should be so slow, although root type of the experimental material used may be a contributing factor. The experiments reported here were all done on nodal roots but most root hair extension rates reported in the literature were obtained on seminal roots of seedling plants (Foehse & Jungk 1983;Brady et al 1993;Bates & Lynch 1996).…”

“…Selection for long and short root hairs in white clover cv 'Tamar' has produced populations with mean lengths of 545 mm and 278 mm (Caradus 1979). Expression of the genetic potential of root hair growth in white clover is presumably modified in a similar fashion to other species by factors such as pH (Ewens & Leigh 1985), nutrient concentration (Foehse & Jungk 1983;Ewens & Leigh 1985;Bates & Lynch 1996;Yan et al 1997), toxic elements (Breckle 1991;Brady et al 1993), water potential (Ekdahl 1953), and rhizosphere organisms (Bowen & Rovira 1976).…”

The Relative Merits of Dolomitic and Calcitic Limestone in Detoxifying and Re Ve Get a Ting Acidic, Nickel- And Copper-Contaminated Soils in the Sudbury Mining and Smelting Region of Canada

“…Increased calcium can reduce the detrimental effects of aluminum on soybean (Lund 1970;Brady et al 1993) and nickel toxicity in corn (Robertson 1985). Calcium-nickel interactions can be complex, and Knight and Crooke (1956) found that the calcium uptake of oat plants, but not of tomato plants, was higher in nickel-contaminated soils .…”