Boron deficiency is a common deficiency of the

micronutrient Micronutrients are essential chemicals required by organisms in small quantities to perform various biogeochemical processes and regulate physiological functions of cells and organs. By enabling these processes, micronutrients support the heal ...

boron Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...

in plants. It is the most widespread micronutrient deficiency around the world and causes large losses in crop production and crop quality. Boron deficiency affects vegetative and reproductive growth of plants, resulting in inhibition of cell expansion, death of

meristem In cell biology, the meristem is a structure composed of specialized tissue found in plants, consisting of stem cells, known as meristematic cells, which are undifferentiated cells capable of continuous cellular division. These meristematic c ...

, and reduced fertility. Plants contain boron both in a water-soluble and insoluble form. In intact plants, the amount of water-soluble boron fluctuates with the amount of boron supplied, while insoluble boron does not. The appearance of boron deficiency coincides with the decrease of water-insoluble boron. It appears that the insoluble boron is the functional form while the soluble boron represents the surplus. Boron is essential for the growth of higher plants. The primary function of the element is to provide structural integrity to the cell wall in plants. Other functions likely include the maintenance of the plasma membrane and other metabolic pathways.

Symptoms

Symptoms include dying growing tips and bushy, stunted growth; extreme cases may prevent

fruit set The annual growth cycle of grapevines is the process that takes place in the vineyard each year, beginning with bud break in the spring and culminating in leaf fall in autumn followed by winter dormancy. From a winemaking perspective, each step i ...

. Crop-specific symptoms include: *''

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

'' - interacting with calcium, may display as "water core", internal areas appearing frozen *''

Beetroot The beetroot (British English) or beet (North American English) is the taproot portion of a ''Beta vulgaris'' subsp. ''vulgaris'' plant in the Conditiva Group. The plant is a root vegetable also known as the table beet, garden beet, dinner bee ...

'' - rough,

canker A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...

ed patches on roots, internal brown rot. *''

Cabbage Cabbage, comprising several cultivars of '' Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.& ...

'' - distorted leaves, hollow areas in stems. *''

Cauliflower Cauliflower is one of several vegetables cultivated from the species '' Brassica oleracea'' in the genus '' Brassica'', which is in the Brassicaceae (or mustard) family. Cauliflower usually grows with one main stem that carries a large, rou ...

'' - poor development of curds, and brown patches. Stems, leafstalks and midribs roughened. *''

Celery Celery (''Apium graveolens'' Dulce Group or ''Apium graveolens'' var. ''dulce'') is a cultivated plant belonging to the species ''Apium graveolens'' in the family Apiaceae that has been used as a vegetable since ancient times. The original wild ...

'' - leaf stalks develop cracks on the upper surface, inner tissue is reddish brown. *''

Celeriac Celeriac (''Apium graveolens'' Rapaceum Group, synonyms ''Apium graveolens'' Celeriac Group and ''Apium graveolens'' var. ''rapaceum''), also called celery root, knob celery, and turnip-rooted celery (although it is not a close relative of the ...

'' - causes brown heart rot. *''

Mango A mango is an edible stone fruit produced by the tropical tree '' Mangifera indica''. It originated from the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South and Southeast As ...

'' - fruits show internal lesions and cracking *''

Pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in late summer into mid-autumn. The pear tree and shrub are a species of genus ''Pyrus'' , in the Family (biology), family Rosaceae, bearing the Pome, po ...

s'' - new shoots die back in spring,

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

s develop hard brown flecks in the skin. *''

Strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid plant cultivated worldwide for its fruit. The genus ''Fragaria'', the strawberries, is in the rose family, Rosaceae. The fruit is appreciated f ...

'' - Stunted growth, foliage small, yellow and puckered at tips. Fruits are small and pale. *'' Swede (rutabaga)'' and ''

turnip The turnip or white turnip ('' Brassica rapa'' subsp. ''rapa'') is a root vegetable commonly grown in temperate climates worldwide for its white, fleshy taproot. Small, tender varieties are grown for human consumption, while larger varieties a ...

'' - brown or gray concentric rings develop inside the roots. *''

Arecaceae The Arecaceae () is a family (biology), family of perennial plant, perennial, flowering plants in the Monocotyledon, monocot order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, all commonly k ...

'' (''

Palm Tree The Arecaceae () is a family of perennial, flowering plants in the monocot order Arecales. Their growth form can be climbers, shrubs, tree-like and stemless plants, all commonly known as palms. Those having a tree-like form are colloquially c ...

'') - brown spots on fronds & lower productivity.

Soil conditions

Boron is present in the soil in many forms, the most common being

boric acid Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula . It may also be called hydrogen orthoborate, trihydroxidoboron or boracic acid. It is usually encountered as colorless crystals or a white ...

(H₃BO₃). An adequate amount of boron in the soil is 12 mg/kg. If the boron content of the soil drops below 0.14 mg/kg then boron deficiency is likely to be observed. Boron deficiency is also observed in basic soils with a high pH because in basic conditions boric acid exists in an undissociated form which the plant is unable to absorb.Boron the Overlooked Essential Element
Soils with low organic matter content (<1.5%) are also susceptible to boron deficiency. Highly leached sandy soils are also characteristic of boron deficiency because the boron will not be retained in the soil.www.agnet.org
Boron toxicity is also possible if the boron content of the soil is high enough that the plant cannot cope with the excess boron. The levels at which boron is toxic to plants varies with different species of plants.Boron Toxicity

Boron requirements

Boron is an essential micronutrient, which means it is essential for plant growth and development, but is required in very small quantities. Although Boron requirements vary among crops, the optimum boron content of the leaves for most crops is 20-100 ppm. Excess boron can result in boron toxicity and the toxicity level varies between plants.

Treatment

Boric acid (16.5% boron), borax (11.3% boron) or Solubor (20.5% boron) can be applied to soils to correct boron deficiency. Typical applications of actual boron are about 1.1 kg/hectare or 1.0 lb/acre but optimum levels of boron vary with plant type. Borax, Boric Acid or Solubor can be dissolved in water and sprayed or applied to soil in blended dry fertilizer. Excess boron is toxic to plants so care must be taken to ensure correct application rate and even coverage. While boron may be sprayed on leaves, excess will cause plant damage. Application of boron may not correct boron deficiency in alkaline soils because even with the addition of boron, it may remain unavailable for plant absorption. Continued application of boron may be necessary in soils that are susceptible to leaching such as sandy soils. Flushing soils containing toxic levels of boron with water can remove the boron through leaching. A boron-containing granular

potash Potash ( ) includes various mined and manufactured salts that contain potassium in water- soluble form.

fertilizer, called Aspire, has been developed to evenly distribute boron through

potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a sa ...

granules. This product contains two forms of boron - sodium borate for quick release and calcium borate for gradual release - to ensure season-long boron availability. These boron-infused potash granules prevent localized boron toxicity, while the granular size allows it to be distributed by common fertilizer equipment along with typical granular NPK fertilizer blends.

Functions

Once boron has been absorbed by the plant and incorporated into the various structures that require boron, the plant is unable to disassemble these structures and re-transport boron through the plant resulting in boron being a non-mobile nutrient. Due to translocation difficulties the youngest leaves often show deficiency symptoms first.

Cell wall

Boron is part of the dRG-II-B complex which is involved in the cross linking for pectin located in the primary cell wall and the middle lamella of plant cells.Toshiro Matsunaga, D.Agr.
This cross linking is thought to stabilize the matrix of plant cell walls.

Enhances protein synthesis

Germination and pollination

The B requirement is much higher for reproductive growth than for vegetative growth in most plant species. Boron increases flower production and retention, pollen tube elongation and germination, and seed and fruit development. A deficiency of B can cause incomplete pollination of corn or prevent maximum pod-set in soybeans.

Sugar translocation

Photosynthesis transforms sunlight energy into plant energy compounds such as sugars. For this process to continue in plants, the sugars must be moved away from the site of their development, and stored or used to make other compounds. Boron increases the rate of transport of sugars (which are produced by photosynthesis in mature plant leaves) to actively growing regions and also in developing fruits. Boron is essential for providing sugars which are needed for root growth in all plants and also for normal development of root nodules in legumes such as alfalfa, soybeans and peanuts.

References

{{DEFAULTSORT:Boron Deficiency (Plant Disorder) Physiological plant disorders Boron