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

• Published in: Plant and soil Vol. 300; no. 1-2; pp. 127 - 136
• Main Authors: Kopittke, P. M, Asher, C. J, Blamey, F. P. C, Menzies, N. W
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.11.2007; Springer; Springer Nature B.V
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biological and medical sciences; chlorosis; Detoxification; Fundamental and applied biological sciences. Psychology; Grasses; Lead; Root and shoot growth; root hairs; Shoots; Soil solution; Tolerance; Chlorosis; Tolerance; Root hairs; Soil plant relation; Root and shoot growth
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-007-9395-1

Although grasses are commonly used to revegetate sites contaminated with lead (Pb), little is known regarding the Pb-tolerance of many of these species. Using dilute solution culture to mimic the soil solution, the growth of signal grass (Brachiaria decumbens Stapf cv. Basilisk) and Rhodes grass (Chloris gayana Kunth cv. Pioneer) was related to the mean activity of Pb²⁺ {Pb²⁺} in solution. There was a 50% reduction in fresh mass of signal grass shoots at 5 μM {Pb²⁺} and at 3 μM {Pb²⁺} for the roots. Rhodes grass was considerably more sensitive to Pb in solution, with shoot and root fresh mass being reduced by 50% at 0.5 μM {Pb²⁺}. The higher tolerance of signal grass to Pb appeared to result from the internal detoxification of Pb, rather than from the exclusion of Pb from the root. At toxic {Pb²⁺}, an interveinal chlorosis developed in the shoots of signal grass (possibly a Pb-induced Mn deficiency), whilst in Rhodes grass, Pb²⁺ caused a bending of the root tips and the formation of a swelling immediately behind some of the root apices. Root hair growth did not appear to be reduced by Pb²⁺ in solution, being prolific at all {Pb²⁺} in both species.