Tolerance of peanut to excess boron

The tolerance ofArachis hypogaea cv. Shulamit to high concentrations of B in nutrient solution, [B]o, was determined under greenhouse conditions that promoted the production of vegetative dry matter. Plants grew in large containers in which a root zone of nutrient solution was separated from a pod zone of soil. Grain yield was reduced at a calculated [B]o-threshold of 0.29 mM, which was associated with a concentration of B in the vegetative shoots that was approximately four times larger than the control. Symptoms of B toxicity occurred on leaves as young as the third unfolded leaf from the shoot apex before the [B]o-threshold. Excess B caused a relatively larger decrease in pod number than in vegetative shoot weight, which was high in all treatments (78 g d.wt/plant) and it did not decrease single grain weight. It was suggested that the tolerance of grain development to excess B was a consequence of the high ratio of vegetative matter to pod number.