What are the symptoms of boron deficiency in common vegetables?

Celery: At first, brown spots appear along the edges of young leaves; in more severe cases, the area near the growing point turns dark brown and dies. The petioles of the outer leaves become withered and aged, with brown stripes appearing on the surface, and the epidermis cracks and turns dark brown. Necrotic brown spots also appear at the base of the petioles and on the roots, and the overall tissue hardens, becoming aged and brittle and easily broken, which is its characteristic feature; in severe cases, the whole plant becomes stunted.

Chinese cabbage: Heart rot of Chinese cabbage can occur with deficiency of either calcium or boron. When heading begins, longitudinal or transverse cracks form on the inner side of the petioles of the 5th to 7th inner young leaves beyond the outer leaves, and the wounds turn brown. More commonly, the midrib of the petiole turns dark brown, and the leaves become severely stunted, rough, and hard.

Tomato: The growing point of the main stem turns yellow, then brown. The tip of the stem becomes aged and easily broken, and sometimes the center turns dark brown. It readily occurs on the buds of the main stem, especially the lateral buds, and elongation stops. During the fruit enlargement stage, deficiency symptoms do not appear on the leaves; instead, sunken cavities form in various places on the fruit, and these areas turn brown and become lignified.

Radish: In mild cases, almost no symptoms are seen in the growth of the aboveground part; after harvest, when cut crosswise or lengthwise, dark brown or blackish-brown streaks form along the central cambium of the fleshy part. This is also called red heart; radishes with red heart are not easily softened even after boiling. In severe cases, the growth of the heart leaves stops while the aboveground part grows luxuriantly; when the root begins to thicken, if a petiole is broken off and observed, it is already aged and withered. The leaves gradually turn yellow, and the heart leaves curl inward, become stunted, and dry up. The white root portion exposed above the ground becomes thick and produces cracking.