36. We know that plants require nutrients. If we supply these in excess, will it be beneficial to the plants? If yes, how/ if no, why?

 


Plants can tolerate a Specific amount of micronutrient. A slight lesser amount of it can cause deficiency symptom and a slight higher amount can cause toxicity. The mineral ion concentration which reduces the cry weight of a tissue by 10° is called toxic concentration. Th. concentration is different for different micronutrients as well as for different plant. e.g. Mn2+ is toxic beyond 600μgg-1 for soyabean and beyond 5300μgg-1 for sunflower
It is very difficult to identify the toxicity symptoms of mineral ion. It is because excess uptake of one element can reduces the uptake of other element at a time.
e.g., manganese (Mn2+) becomes toxic when absorbed by plants in higher amounts. The toxicity is expressed in form of brown spots surrounded by chlorotic vein.
It is due to the following
(i) Reduction in uptake of Fe3+ and Mn2+.
(ii) Inhibition of binding of Mn2+ to specific enzymes.
(iii) Inhibition of Ca2+ translocation in shoot apex.
Thus, excess of Mn2+ causes deficiency of iron, magnesium and calcium.