Clover (Trifolium spp.). Plants are weak, with thick stems that are swollen close to the growing point, and leaf margins often look burnt (78). Symptoms of boron deficiency in red and alsike clover may occur as a red coloration on the margins and tips of younger leaves; the coloration gradually spreads over the leaves, and the leaf tips may die (65).
Corn (Zea mays L.). Boron deficiency is seen on the youngest leaves as white, irregularly shaped spots scattered between the veins. With severe deficiency these spots may coalesce, forming white stripes 2.5 to 5.0 cm long. These stripes appear to be waxy and raised from the leaf surface (79). Interruption in the boron supply, from 1 week prior to tasselling until maturity, curtailed the normal development of the corn ear (80).
Oat (Avena sativa L.). Pollen grains are empty (70).
Peanuts or groundnut (Arachis hypogaea L.). Boron deficiency resulted in hollow-heart in peanut kernels at a few locations in Thailand (81).
Pea (Pisum sativum L.). Leaves develop yellow or white veins followed by some changes in interveinal areas; growing points die and blossoms shed (82). Unpublished data of Gupta and MacLeod (83) showed that boron deficiency in peas resulted in short internodes and small, shrivelled new leaves.
Potato (Solanum tuberosum L.). Deficiency results in the death of growing points, with short internodes giving the plant a bushy appearance. Leaves thicken and margins roll upward, a symptom similar to that of potato leaf roll virus (84). Boron deficiency resulted in rosetting of terminal buds and shoots, and the new leaves were malformed and chlorotic (85).
Radish (Raphanus sativus L.). Deficiency of boron in radish is also known as brown-heart, manifested first by dark spots on the roots, usually on the thickest parts (76). Roots upon cutting show brown coloration and have thick periderm (71).
Rutabaga (Brassica napobrassica Mill.). The boron deficiency disorder in rutabaga is generally referred to as brown-heart. Upon cutting, the roots show a soft, watery area (Figure 8.3). Under severe boron deficiency the surface of the roots is rough and netted, and often the roots are elongated (86). The roots are tough, fibrous, and bitter, and have a corky and somewhat leathery skin (58).
Snapbean (Phaseolus vulgaris L.). There is a yellowing of tops, slow flowering and pod formation (71).
Soybean (Glycine max Merr.). Boron deficiency results in necrosis of the apical growing point and young growth; the lamina is thick and brittle; and floral buds wither before opening (87). Boron deficiency induced a localized depression on the internal surface of one or both cotyledons of some seeds and resembled the symptoms of hollow-heart in groundnut seeds (88).
Sunflower (Helianthus annuus L.). There is basal fading and distortion of young leaves with soaked areas and tissue necrosis (25).
Tomato (Lycopersicon esculentum L.). The growing point is injured; flower injury occurs during the early stages of blossoming, and fruits are imperfectly filled (72). Failure to set fruit is common, and the fruit may be ridged, show corky patches, and ripen unevenly. Wheat (Triticum aestivum L.). A normal ear forms but fails to flower (70). In the case of severe boron deficiency, the development of the inflorescence and setting of grains are restricted (87).
Cotton (Gossypium hirsutum L.). Boron deficiency causes retarded internodal growth (89). The terminal bud often dies, checking linear growth, and short internodes and enlarged nodes give a bushy appearance that is referred to as a rosette condition (90). Bolls are deformed and reduced in size. Root growth is severely inhibited, and secondary roots have a stunted appearance (91).
Sugar Beet (Beta vulgaris L.). Deficiency results in retarded growth, and young leaves curl and turn black (92). The old leaves show surface cracking, along with cupping and curling. When the growing point fails completely, it forms a heart rot (92).
Tobacco (Nicotiana tabacum L.). Boron deficiency results in interveinal chlorosis, dark and brittle newly emerging leaves, water-soaked areas in leaves, and delayed flowering, and formation of seedless pods (93). Tissues at the base of the leaf show signs of breakdown, and the stalk toward the top of the plant may show a distorted or twisted type of growth. The death of the terminal bud follows these stages (94).
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