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Eight cassava (Manihot esculenta) cultivars were grown with or without mycorrhizal inoculation in flowing solution cultures containing approximately 0.1, 1, 10 or 100 μM phosphate. Rice (Oryza sativa), maize (Zea mays), cowpea (Vigna unguiculata) and French bean (Phaseolus vulgaris) were included in the experiment for comparative purposes. Cassava required a higher external phosphorus concentration for maximum yield (≥ 10 μM) than the other species (≥ 1 μM) regardless of the inoculation treatments. Roots of inoculated cassava plants were heavily infected with VA endophytes at 0.1 and 1 μM phosphate, but not at 10 or 100 μM. Non-inoculated cassava plants were free of infection, and no infections were observed in any treatment on the other species. At 1 μM phosphate, infection of cassava roots was associated with large increases in whole plant dry wt, concentration of phosphorous in tops and roots, and total phosphorus uptake. At 0'1 #M phosphate there were also substantial increases in phosphorus concentration in tops and roots but the infected cassava plants were still severely phosphorus deficient and growth was not improved. The results are discussed in relation to the present state of knowledge about the phosphorus nutrition of cassava. [ABSTRACT FROM AUTHOR]

Low activities of the monomeric aluminium (Al) species, Al3+, Al(OH)22+ and Al(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 μM 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 μM, taproot elongation and lateral root development of soybean was suppressed in solution with 500μM 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 μM 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. [ABSTRACT FROM AUTHOR]