ALUMINUM ROOT SYSTEM DAMAGES AND PHOSPHORUS UPTAKE BY BLUEBONNET

This work aimed to evaluate the morphological changes caused by aluminium (Al) stress, on Bluebonnet roots. An experiment was carried out in a greenhouse, using pots (2L) containing a altered Hoagland nutritive solution. The bluebonnet plants (Lupinus angustifolius L.) cv. IAPAR 24, were germinated in sand and, kept in the solution at 50% for two weeks. With 15 days, these plants were submitted to Al stress, given the treatment a time variation of 0-33, 13-33, 23-33, 0-11 and 0-22 days. In the periods without Al or plants in no Al at all, the plants grew in a complete nutritive solution. The plants that were not submitted to Al stress presented a large lateral ramification (10,45m of the total lenght), thin roots (0,63mm radiuns) and light roots, with 0,29% of P in the shoot. In the presence of Al all the time, there was a lowering of branching (0,56m), a large increase on radius (1,76mm) and, presence of exudates and salt precipitate on the epidermis, fissures, scaling and necrosis with a coralloid aspect and, phosphorus concentration in the shoot was very low (0,01%). The use of Al in the initial periods reduced, significantly, the emission of roots due to the thickening of the growing points. These damages were reversible and its extension depended upon the time of Al exposure. An Al free environment at the initial phase gave favorable conditions to nutrients uptake, specially P, with a peak in the root system growing capable of tolerating future stresses, demonstrating that toxicity in bluebonnet was much more severe in this phases.

Lupinus angustifolius L.; Al stress; phosphorus


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