In 1923, K. Warington discovered that boron is an essential element for plants. The content of boron in crops is generally among 2‱-3‱ of dry weight or 1% of dry weight. Among them, legumes and cruciferae have the highest boron content, while gramineous crops have lower boron content. Among the various organs of crops, flowers and leaves have the highest boron content, followed by stems, roots, and fruits, and seeds have the least content.

Boron is not a component of various organic matter in crops, but it can enhance some important physiological functions of crops. The supply of boron is sufficient, the plants grow luxuriantly, the seeds are full, the root system is good, and the harvest is guaranteed; on the contrary, the insufficient supply of boron will cause serious crop yield reduction or even no harvest.

The effect of boron elements on crop growth:

1. Cell elongation and tissue differentiation

There is a clear interaction between auxin (indole acetic acid) and boron. Boron inhibits indole acetic acid oxidase activity in roots. Under the stimulation of indole acetic acid, root elongation was normal. Indole acetic acid in green plants is only formed in vascular plants, and it participates in the differentiation of xylem vessels. Therefore, the general demand for boron is also limited to vascular plants. However, the woody part of the boron plant is weakened. Stem cambium cell division is strengthened and cambium cells proliferate.

2. Enzyme metabolism and wood formation

The accumulation of phenolic compounds inhibits the activity of indole acetic acid oxidase. Boron can complex with phenolic compounds to overcome the inhibitory effect of phenolic compounds on indole acetic acid oxidase. In the process of lignin formation and xylem vessel differentiation, boron inhibits the activity of hydroxylase phenolic compounds.

3. Carbohydrate transportation and protein metabolism

Boron has two roles in carbohydrate metabolism: the formation of cell wall material and sugar transport. Boron can promote the circulation of glucose-1-phosphate and the conversion of sugar. Boron and calcium together play the role of "intercellular glue". Boron affects the synthesis of RNA, especially uracil.

New leaves of boron-deficient plants have low protein content, which is limited to the cytoplasm, while chloroplast protein content is not affected. Therefore, chlorosis of boron-deficient plants is not common. Boron can strengthen crop photosynthesis and promote the formation of carbohydrates.

When crop boron is insufficient, it will cause a large accumulation of carbohydrates such as sugar and starch in the leaves, which cannot be transported to seeds and other parts, thereby affecting crop yields.

4. Root growth and development

Boron can promote the normal development of vascular bundles in the roots of leguminous crops and promote the adequate supply of carbohydrates by rhizobia, thereby enhancing the nitrogen-fixing ability of leguminous crops, increasing the protein content, increasing the fiber content of hemp crops, and improving it Quality.

Boron can form complexes with 6-phosphogluconic acid in crops, preventing the formation of 4-phosphoerythronic acid (which is an important raw material for the formation of acid compounds). When crops are deficient in boron, organic acids accumulate in the roots. The cell differentiation and elongation of the apical meristem are inhibited, and corkization occurs, causing root necrosis.

Boron can make the root tips and stem growth points of crops and other meristematic tissues grow normally. Boron and alcohols, sugars and other compounds can form peroxides, thereby improving the supply of oxygen to the roots of crops. Especially in the case of hypoxia, the application of boron fertilizer can promote the development of crop roots. Therefore, for roots and tuber crops such as sugar beets, potatoes, radishes, etc., the effect of applying boron fertilizer is better.

5. Crop resistance

Boron can enhance the drought and disease resistance of crops. Boron has the effect of controlling water in crops, improving the viscosity of sunflower, buckwheat and other crop protoplasms, and enhancing the ability of colloids to bind water.

The application of boron can promote the formation of vitamin C, and the increase of vitamin C can increase the stress resistance of crops. Insufficient boron supply to crops reduces stress resistance and disease resistance, which will cause crops to produce certain physiological diseases.

The application of boron can greatly reduce the incidence of these diseases in these crops: such as the "heart rot" of sugar beet, the "brown rot" of cauliflower and radish, the "scab disease" of potatoes, the "stem cracking" of celery, and the "brown rot" of celery. Stem disease, hollow of radish, poor growth of cabbage, spinach, "brown spot" of sweet potato, "blight" of flax, "white rot" of sunflower, and "charcoal spot" of kidney bean Wait.

6. Early maturity and modification of crops

Boron can promote early maturity of crops. According to relevant domestic reports, under the influence of boron, the time for winter wheat to pass through spring flower will be shortened by eight days.

Applying boron to cotton increases the number of flowers before frost, and improves the yield and fiber quality of seed cotton. The application of boron to corn and rice advances the main growth periods, and the seeds mature about five days earlier. The effect of boron in promoting premature maturity is particularly noticeable for cold mountain areas and double maturity. The development of agricultural production in the three-crop system area has certain positive significance.

Rape boron application can reduce protein and increase fat content. Boron on cucumbers and tomatoes can increase the vitamin C content. Applying boron to apples and citrus can increase the sugar content and reduce the acid content.

The application of boron fertilizer in hybrid seed production can make the maturity period of the reproductive organs of the male and female plants tend to be the same, and promote a substantial increase in seed production; at the same time, it can also increase the seed setting rate of distant hybrids.

7. Pollen germination and pollen tube growth

The indirect effect of boron may be related to the increase of sugar content in nectar and the change of its composition, making the flowers of insect-borne plants more attractive to insects.

The direct effect of boron is closely related to the pollen production ability of anthers and the viability of pollen grains. Boron can stimulate pollen germination, especially pollen tube elongation.

Boron can promote the normal development of the reproductive organs of crops and is conducive to flowering and fruiting. Proper application of boron fertilizer can accelerate the development of floral organs, increase the number of pollen, and promote the germination of pollen grains and the growth of pollen tubes.

Rape lacks boron and causes "flowers without fruit". The results prove that the male and female gametophytes of rapeseed that lack boron and can bloom normally, but can’t bear normal fruit, are well developed and the ovary structure is complete, but the stigma loses attachment due to the lack of boron. The ability of pollen, the anther wall is destroyed and loses the ability to disperse, the pollen sticks into clumps and the development rate is low, so the rape can only bloom but cannot bear fruit. This result strongly proves the importance of boron for the growth of reproductive organs.

In agricultural production, in addition to the symptoms of "flowers without fruit" in rapeseed, the "untwisting syndrome" of wheat, the "buds but not flowers" of cotton, the "fruits but not kernels" of peanuts, and the falling flowers and fruits of fruit trees, etc. It is caused by a lack of boron.