Necessary for cell wall formation, membrane integrity, calcium uptake and may aid in the translocation of sugars. Boron affects at least 16 functions in plants. These functions include flowering, pollen germination, fruiting, cell division, water relationships and the movement of hormones. Boron must be available throughout the life of the plant. It is not translocated.
Deficiencies kill terminal buds leaving a rosette effect on the plant. Leaves are thick, curled and brittle. Fruits, tubers and roots are discolored, cracked and flecked with brown spots. B deficiency may occasionally occur in outdoor soils. The symptoms appear first at the growing shoots, which die and turn brown or grey. The shoots may appear "burned," and if the condition occurs indoors, you might think the lights have burned the plant. A sure sign of boron deficiency is that, once the growing tip dies, the lateral buds will start to grow but will also die.
High boron causes many cellular activities to be partially inhibited and the toxicity to mature tissues is not considered to arise from the disruption of a single process, but from the accumulated retardation of many cellular processes.
The range between a correct application rate, and a toxic one is not large, so it is relatively easy to apply too much boron. Because of this, it is very important to get uniform mixing and application, especially when applying in concentrated bands or foliar. Because of the slow transport of B in the plant, symptoms generally appear on the older leaves and consist of margin or leaf tip chlorosis, browning of leaf tips, which is quickly followed by the death of the affected tissue or defoliation. The critical plant level for toxicity can range from 10 - 50 ppm in sensitive plants and as high as 200 ppm in tollerant ones.
Micronutrient and Immobile element
Boron is important when dealing with maturation, pollen germination and seed production. As well as keeping calcium in soluble forms and keeping the stems, stalks, branches strong. Born keeps good colour on the leaves and helps produce the plants structure.
Boron also aids in cell division and protein formation.
Boron deficiencies will show up first in younger leaves (they may turn yellow), then moves up the plant. Boron deficiency can resemble calcium deficiency. Stunting, discolouration, possible death of the growing tips, bud abortion and development. The Roots will show a stunted with swollen short secondary roots, leaves distorted, sometimes bronzed or scorched. Tip of the shoot dies; stems and petioles are brittle. Boron deficiency plants are easy to tell, because of the spotting the leaves show like a strawberry mark and or splashes of the marking. Boron-deficiency symptoms first appear at the growing points.
They also can show signs of newer growths turning gray and or dying, bud deformed, curling of the leaves which are often spotted and discoloured. Newer growths appear to look like they are burnt.
They can show signs of hollow stems along with yellowish to brownish colour leaves. Dead (Necrotic) spots develop between leaf veins, as well as the leaves becoming thick. The leaves will wilt with necrotic and chlorotic spotting. Boron is poorly absorbed with low potassium content. First signs of the deficiency are abnormal growth tips. Having not enough boron can also invite troubles for fungus problems from the internal tissues to rot away, as well as the root hairs along with them being discoulored.
To avoid having a Boron deficiency try to keep the ph below 7 and to improve the moisture as well as retaining light soils.
Too much boron in your plants can produce a lot of problems. The leave tips turn yellow progressing inwards causing the plant to soon
die slowly along with leaves dropping a lot.
Can show same signs as if a magnesium deficiency, but only happens on newer growths. Parts affected by a boron deficiency are: Growing points and young leaves.