How to make citrus color better and what medicine to use during the coloring period of citrus

1. Principle of citrus color change

We all know that color is related to pigments. Leaves are green because of the presence of chlorophyll, and young fruits are green because they contain a large amount of chlorophyll. , and then the color changes because the chlorophyll slowly decreases, while the carotenoids, flavonoids, lycopene and anthocyanins that produce yellow and red colors gradually increase.

Now that we know the principle of color change, what conditions will affect these biochemical reactions and lead to the increase of anthocyanins and carotenoids?

1) Sugar

Anthocyanins will show different colors under different pH conditions. In autumn, when fruits mature, sugar content increases, and cells become acidic. Correspondingly, anthocyanins will also appear red.

Sugar and anthocyanins have a positive correlation, so the accumulation of sugar content helps the coloring of anthocyanins. Sugar content generally relies on the accumulation of photosynthesis in the leaves. The larger the leaf area, the better the coloring. , but too many leaves will cause the fruit tree to grow elongated. If the leaves continue to grow, a certain amount of sugar will be used for growth, which is not conducive to coloring.

2) Light

Light will affect the synthesis of sugar and indirectly affect anthocyanins to a certain extent. In addition, light will also activate the expression of genes to promote anthocyanins and anthocyanins. Accumulation of carotene.

As can be seen from the picture, as the citrus fruit matures, the chlorophyll content in the peel continues to decrease and the carotenoid content continues to increase. The shading treatment reduces the chlorophyll and carotenoid content. The shading-light treatment It can increase the carotenoid content compared to the shading treatment, so light promotes the accumulation of carotenoids.

Then why is the brightness obviously higher when using bags to block light? This is because we usually use brown paper bags to cover them, so the light can still be refracted in (only black will absorb a lot of light). It also creates an environment isolated from the outside world, avoiding some pesticide pollution and sandstorm damage.

Except for pomelo, most varieties require light to improve coloring.

3) Temperature

20° is the optimum temperature for carotenoids. The nights in subtropical autumn and winter are cool, and the juice and soluble solids of most citrus varieties increase, accelerating the decomposition and decomposition of chlorophyll. Carotenoid synthesis, which is related to the production of ethylene due to low temperature cold damage.

Some studies have also confirmed that low temperature will promote the synthesis and accumulation of anthocyanins, and high temperatures will lead to reduced synthesis and increased decomposition of anthocyanins.

4) Moisture

The amount of moisture affects the quality of the fruit, but prolonged drought during the fruit expansion period will cause the fruit to become shriveled, lack water, and stunt development; if there is too much water It may also cause fruit cracking. Even if fruit cracking does not occur, excessive water and reduced soluble solids content will make the taste lighter and affect storage.

5) Mineral elements

The elements that have a greater impact on the content of anthocyanins are nitrogen, phosphorus, calcium, manganese, and zinc. Nitrogen and anthocyanins are negatively correlated. That is to say, the more nitrogen, the less anthocyanins; the phosphorus content is positively correlated with anthocyanins. The more phosphorus, the more anthocyanins, and the better the color.

In addition, boron and calcium elements can promote the transportation of tree nutrients; magnesium elements can promote photosynthesis and the formation of anthocyanins in citrus leaves; molybdenum elements can promote photosynthesis and increase reducing sugar content.

6) Hormones

Ultimately, fruit maturity depends on the coordination of plant hormones such as ethylene, gibberellins, and abscisic acid produced by the plant itself. Ethylene and abscisic acid (ABA) promote aging, while gibberellin (Ga) and naphthylacetic acid (NAA) promote growth at low concentrations.

2. Uniform color change method

1).

Control the application of nitrogen fertilizer, increase the application of phosphorus and potassium fertilizer, and supplement appropriate amounts of calcium, boron, magnesium, molybdenum and other micro-fertilizers. Nitrogen helps in the synthesis of chlorophyll, phosphorus helps in expansion and color change, potassium increases sugar content and promotes coloring, and calcium increases fruit hardness and single fruit weight.

2). Spray biostimulants such as amino acid alginic acid, fish protein, and polypeptides. It can directly supplement trace elements and carbon sources and indirectly improve the sugar conversion rate.

3). Light promotes the accumulation of carotenoids; insufficient water causes the fruit to dry out and stunted development; too much water can easily crack the fruit and make the fruit taste lighter; low temperature will promote the synthesis and accumulation of anthocyanins, and high temperature will cause The synthesis of anthocyanins is reduced and the decomposition is increased.

3. Can hormones be used?

We all know that during the ripening process of fruits, they will produce hormones such as ethylene and gibberellins, so they are combined with pesticides, herbicides and other Plant growth regulators are much less toxic than pesticides. And in some fruits such as bananas, it is almost routine to use "ethephon". If not, you have to wait until the bananas ripen before picking, and then the bananas will often rot during transportation. However, many medical experts believe that hormone-induced off-season vegetables and fruits have little effect in the short term, but long-term consumption will cause side effects on the human body.