Can soil hardness alleviate aluminium stress in plant?

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This study was aimed to know 1) physical stimuli to root tips can increase production of root-tip mucilage, 2) such an increase can reduce Al-accumulation in the root tips, and consequently 3) stress impact of Al can be alleviated. To create the presence or absence of the stimuli to roots, maize (Zea mays L.) plants were hydroponically grown with or without sand, respectively. Plants grown with sand had numerous root tips with mucilage besides its volume per tip was also larger comparing to ones without sand, indicating that the presence of the stimuli can promote mucilage production. Giving AlCl3at various concentrations, Al injury could occur only at 10 Μm without sand but was not fully induced even at 1000 Μm with sand, revealing that Al toxicity is alleviated in the presence of the root stimuli. Root tips collected from conditions in the presence or absence of sand were divided into ones with or without mucilage, and then exposed to AlCl3 solution at 1000 Μm. The tips with mucilage showed lower Al -accumulation than ones without it, suggesting that mucilage could protect the tip against Al. On the other hand, there was no significant difference in Al-accumulation between the tips with mucilage and ones once removed it. To seek the reason for this, the tips once removed mucilage were monitored and found that visible mucilage could recover within 5 minutes. We have assumed that such a rapid recovery of mucilage is responsible for no significant effect of mucilage removal.