Silicon alleviates ammonium toxicity in cauliflower and in broccoli

Plant growth may be higher with a nitrate (NO3-) and ammonium (NH4+) ratio (N-A ratio), in relation to a particular form of N. However, the NH4+ can be toxic. In order to alleviate NH4+ toxicity in plants, silicon (Si) can be used. To evaluate the effect of N-A ratios and Si in cauliflower and broccoli, the plants were grown in hydroponic system, using coarse sand substrate. Randomized block design was used, with four replications, in a 3 x 2 factorial scheme, corresponding to total N concentration of 15 mmol L-1, with N-A ratios of 100/0, 50/50 and 0/100, in the absence and presence of Si (2 mmol L-1). The NH4+ source was ammonium chloride and as Si source, stabilized sodium and potassium silicate. The results suggest that in cauliflower, the alleviation of NH4+ toxicity using Si can be noticed through the increase of the physical integrity of the membranes and in broccoli, the alleviation of NH4+ toxicity is associated most with the water use efficiency. Si alleviates NH4+ toxicity in cauliflower when the total N concentration is 15 mmol L-1 and 50% is supplied in the form of NH4+. In broccoli, Si improves the effect of NO3- and alleviates NH4+ toxicity.