Boron nutrition and mobility, and its relation to hollow stem and the elemental composition of greenhouse grown cauliflower

Publisher Website
Google Scholar
Abstract
The growth and elemental composition of various parts of cauliflower (Brassica oleracea var botrytis cv White Top) plants were investigated under greenhouse conditions with plants grown in vermiculite medium as a function of B added at concentrations of 0.0, 0.25, 1.0, 2.5 and 12.5 mg L‐l. Optimal plant and head yield, and the maximum fresh weight harvest index were found at 1.0 mg B L‐l; B levels in the head, and old and young leaves were 41, 543 and 145 μg g‐1 DM respectively. Above and below 1.0 mg B L‐l foliar symptoms of toxicity and deficiency were evident. In the absence of added B, the head also showed slight internal signs of necrosis and browning, and curd surface discoloration, symptoms which may be associated with the hollow stem disorder under field conditions. In this case, the B levels were 21, 35, 48 and 55 μg g‐1 DM respectively in the head, and old, young and intermediate leaves. Comparison of the relative element composition of younger tissues to old leaves indicated that the former, particularly the head, were supplied with nutrients principally by the phloem and that B was relatively phloem‐immobile. However, indirect assessment of element retranslocation, based on the ratio of its concentration in young leaves or head: old leaves, showed that B is remobilized under B deficiency. The B concentration of the nutrient solution also caused changes in the retranslocation of other elements, particularly the largely phloem‐immobile elements, to young leaves. It is concluded that the B levels of the old leaves, and the young tissue, particularly the head are respectively the most reliable indicator of B toxicity and deficiency.