and Plant Nutrition Home
used by plants:
B(OH)4- (at high pH)
is the dominant form in soils thought to be absorbed by higher plants.
metabolism of carbohydrates
certain dehydrogenase enzymes
in formation of pollen tube and feeder roots
in translocation of Ca, sugars, and plant hormones
the synthesis of nucleic acids
for cell division and development
foliage range for apple leaves:
normal levels <20ppm
levels >80 ppm
fruit range (tentative):
fruit samples at harvest: deficient levels are < 10 mg/kg (ppm);
excessive levels for Jonathan, McIntosh >25 ppm and for Delicious and
G. Delicious >60 ppm; others are intermediate
is mobile in soils
B can be easily leached from acid sandy soils. Boron availability is
lowest between soil pH 7-9. Lime induced B deficiency is possible.
and blossom content are more sensitive indices of tree B status than are
soil or leaf B content.
remobilized within plant
leaves are affected first and are often small, stiff, thick, brittle
leaves with smooth margins. Main
veins may be large, lacking chlorophyll, cracked, or corky (NY pub). Chlorosis and
cupping are common. Leaves
may form rosettes at nodes.
broom" often occurs as sidebuds bread and start developing.
B concentrations 12 ppm or less, terminal buds die and shoot dieback
takes place. Additionally,
internal bark necrosis may develop in trees deficient in B.
deficiencies may appear because Ca translocation is impaired at
insufficient B concentrations.
B deficiency decreases the rate of water absorption, root growth, and
translocation of sugars in plants.
risk of B deficiencies on:
symptoms: reduced or no yield; increased internal breakdown after
harvest, increased watercore
development. At leaf
concentrations between 60-70ppm, fruit may ripen early and fall
symptoms: same as deficiency symptoms.
updated: 14 February, 2001