1. Answering questions

Grapefruit is also known as pomelo, Wendan, Xiangluan, Zhuluan and Neizi. The flowering period is April-May and the fruiting period is September-December.

II. Name and overview

Grapefruit (scientific name: Citrus maxima (Burm) Merr), also known as pomelo, Wendan, Xiangluan, Zhuluan, Neizi, etc. It is a citrus tree of Rutaceae. The shoots, leaf backs, pedicels, calyx and ovary are all pilose, and the leaves are usually dark purple-red, and the shoots are flat and angular. The leaves are thick, dark green, oval or oval; Racemes, sometimes with axillary single flowers; The buds are purplish red and thin milky white; Calyx irregularly 5-3-lobed; The style is thick and long, and the stigma is slightly larger than the ovary. The fruit is spherical, oblate, pear-shaped or broadly conical, and the transverse diameter is usually more than 1 cm; There are more than 2 seeds, some of which are seedless, irregular in shape, usually almost rectangular; Cotyledons are milky white and single embryo. The flowering period is April-May and the fruiting period is September-December.

III. Morphological characteristics

The shoots, leaf backs, pedicels, calyx and ovary are all pilose, and the shoots are usually dark purple-red, flat and angular. The leaves are quite thick, dark green in color, broadly oval or oval, and the leaves of Hebei are 9-16 cm long and 4-8 cm wide, or larger, with blunt or round tips, sometimes short tips, and round bases. The wings are 2-4 cm long and .5-3 cm wide, and the wings of individual varieties are very narrow.

racemes, sometimes with axillary single flowers; The buds are purplish red and thin milky white; Calyx irregularly 5-3-lobed; Petals are 1.5-2 cm long; Stamens 25-35, sometimes some stamens are sterile; The style is thick and long, and the stigma is slightly larger than the ovary.

The fruit is round, oblate, pear-shaped or broadly conical, with a transverse diameter of usually more than 1 cm, light yellow or yellow-green. The hybrid is vermilion, with a thick or thin skin, spongy, large oil cells, protruding, solid but soft fruit core, 1-15 or up to 19 petals, and the juice cells are white, pink or bright red, with few milky yellow. There are more than 2 seeds, some of which are seedless, irregular in shape, usually rectangular, with thin upper part and often truncated, full lower part, mostly stunted, with obvious longitudinal ribs, ivory cotyledons and single embryo.

iv. Growth environment

1 Growth and fruiting habits

The root system of pomelo is composed of taproot, lateral root and fibrous root. The growth and yield of pomelo trees mainly depend on the quantity and quality of fibrous roots. Pomelo, like other citrus, belongs to mycorrhizal plants, and its roots mainly rely on mycorrhizal fungal hyphae to absorb nutrients and water. Therefore, improving mycorrhizal growth conditions and promoting mycorrhizal growth is an important work in its orchard management.

The bud of pomelo is precocious, and it can be sprouted many times a year, which is easy to form a crown. There are dormant hidden buds on the branches of pomelo, which will be stimulated to germinate and develop into new branches, which is the basis for renewing and rejuvenating the tree.

In Guizhou, pomelo usually shoots three times a year, namely, spring shoots, summer shoots and autumn shoots. The branch angle of pomelo has a great influence on the growth and fruiting. The branch angle is small, the branch tip is erect, the top advantage is strong, the growth is vigorous, and the nutrient accumulation is less, which is not conducive to flower bud differentiation, while the horizontal branch is opposite to the drooping branch. Therefore, in agricultural measures, the branch pulling method is often used to increase the branch angle and promote early fruiting.

The main fruiting branches of pomelo are spring shoots, especially leafless spring shoots in the crown (also called bare branches because of few leaves), which are the main fruiting branches of pomelo. Autumn shoots can also be used as fruiting mother branches, but when there are many fruits, autumn shoots are less sprouted.

The fruiting branches of pomelo are mostly inflorescence branches, that is, leafy inflorescence branches and leafless inflorescence branches. The fruit branches of leafy inflorescences are fruiting branches with leaves. Except for the flowers at the top, there are many buds in the axils of other leaves, or a raceme grows at the top of new shoots. The number of flowers in leafy inflorescences varies from 4 to 8. The leafless inflorescence has no leaves or only 1-2 tiny leaves on the branches, and there are 3-45 flowers on the branches. ?

2 Requirements for environmental conditions

Pomelo trees have strong adaptability to temperature, with annual average temperature of 16.6-21.3℃, January average temperature of 5.4-13.2℃, annual accumulated temperature of ≥1℃ of 53-75℃ and absolute low temperature above -11.1℃. However, the annual average temperature is 18-2℃, the January average temperature is 7-9℃, the annual accumulated temperature is ≥1℃, and the absolute minimum temperature is above -5℃. When the soil temperature reaches 12-13℃, the root system of pomelo begins to grow, and 23-3℃ is the best soil temperature for its growth and absorption of water and nutrients. Below 7℃ and above 37℃, the root system of pomelo grows weakly or stops. The root system began to die at 45-5.5℃. Low temperature, rainy weather or unusually high temperature during flowering of pomelo trees will affect flower quality, pollination and fertilization, aggravate physiological fruit drop, and lead to low fruit setting rate and low yield. After the fruit enters the expansion period, it is also greatly influenced by temperature. When other environmental conditions are met, the temperature is appropriate, the fruit expands quickly and the weight of a single fruit is high. On the contrary, the fruit expansion is blocked, especially the high temperature is accompanied by drought, which seriously affects the yield.

Pomelo trees have a wide adaptability to soil types and soil pH, and the soil with good permeability, loose soil, porosity above 1% and oxygen content above 6%. Soil hardening and excessive moisture lead to insufficient oxygen in the soil, and also produce hydrogen sulfide, nitrous acid, ferrous oxide and other toxic roots, which make the roots rot. The soil layer is deep and fertile, and the organic matter in the main root distribution layer is preferably 5%, and the appropriate pH is 6-6.5.

the requirement of air humidity for pomelo is about 75%, which is suitable for the growth and development of pomelo. In the growing season, the suitable soil moisture is 6%-8% of the field capacity. If it is as low as 4%-5% of the field capacity, leaves will roll, but too much soil moisture will cause insufficient soil air and affect root growth.

pomelo is shade-tolerant in citrus, but it still needs good lighting conditions to achieve high quality and high yield. However, pomelo should not be exposed to strong light, and diffuse light is more beneficial to the photosynthesis of pomelo than direct light.

V. Distribution range

All areas south of the Yangtze River in China, and the northernmost areas are found in Xinyang and Nanyang, Henan Province, all of which are cultivated. Southeast Asian countries have planted it.

VI. Main varieties

1. Orange

Also known as Huazhou Orange and Huazhou Xianju. The fruit is pilose, the peel is thicker than other varieties of pomelo, the flesh is pale yellow and white, and it tastes sour and bitter, so it is unbearable to eat raw. The fruiting period is October-November.

Guangdong (Huazhou, Maoming). Guangxi (Bobai, Luchuan, etc.) and Hunan (Qianyang) also have them. The pericarp of orange is a traditional Chinese medicine, which is famous for its production in Huazhou, hence its name. The young fruit is called orange embryo after drying, and the flower is called orange flower after drying. Picking the fruit before the summer heat, soaking, drying, slicing, baking with fire and pressing are equal operations, that is, orange peel. There are two kinds of tangerines: straight-hairy tangerines and auxiliary-hairy tangerines. The former is from grafted fruit trees, and the latter is from seedlings or budded fruit trees.

According to research, Huazhou Orange in Guangdong Province was first planted in the Liang Dynasty and will have a history of 1,5 years.

6. Shatian pomelo

The fruit is pear-shaped or gourd-shaped, with a slightly flat top, obvious rings and radial grooves, a narrow and prolonged neck-shaped pedicle, crisp pulp, rich and sweet taste, but less water and many seeds. After the end of October, it is a medium-mature variety.

mainly produced in Guangxi (rongxian, Guilin, Liuzhou and other places).

rich in soluble solids and vitamin c, it is the best among pomelos.

There is a tendency of self-pollination, so sour pomelo should be planted in the plantation to cross-pollinate and improve the fruiting rate.

13. Wendan

The fruit is oblate, slightly concave at the top, slightly narrow at the base, with raised ridges at the pedicle, thin and smooth peel, small and dense oil cells and slightly sour pulp flavor.

it is mainly produced in Fujian (Zhangzhou area), and is planted in Taiwan Province and Zhejiang.

1. Pingshan pomelo

The fruit is oval, with two shoulders cut, the top of the fruit is nearly flat, the pedicle has convex edges, the skin has large and convex oil cells, the sponge layer and pulp are reddish, the core is empty, the meat is crisp, the water is rich, the taste is sweet and the acidity is low. The fruit period is the same as that of Wendan.

it is mainly produced in Fujian (Zhangzhou area).

⒌ Jinxiang pomelo

is also called Changyou, Xiangyou, Jingua pomelo or Cili sweet pomelo. The fruit is oval, the top of the fruit is flat, the fruit base is short and neck-shaped, the peel is smooth, golden yellow, quite thin, easy to peel off, the core is big and empty, and the pulp is beige, soft and very sweet. The fruiting period is in late September.

mainly produced in Hunan (Cili, Changde, Shimen and other places).

The peel has high oil content, and the oil has a special aromatic smell, which can be used as the raw material of essential oil.

[6] Anjiang pomelo

The fruit is spherical or conical, with a flat top, a narrow base, a sunken pedicle, raised ridges around it, a thick peel, large oil cells, a hollow core, white pulp, crisp, juicy, moderate sweetness and sourness, and a fragrant smell. The fruiting period is about the end of October

and it is mainly produced in Hunan (Qianyang, Shaoyang and other places).

1. The fruit shape of Jin Lan pomelo

is similar to that of Shatian pomelo, but the top of the fruit is very short or nearly neck-less, the top of the fruit is round and slightly flat, the pedicle is shallow and sunken, and the periphery is raised. The peel is thin, the core is small, the pulp is tender, refreshing, juicy, sweet and sour, with aroma and many seeds. The fruiting period is from late October to November.

mainly produced in Jiangxi (Shuangjin, Shuixin and other places).

The fruit of Jin Lan pomelo seedling tree is very large, weighing 2 kg, with stout stalk, smooth and bright skin, very sour pulp, often with tingling tongue and sometimes light green juice cells. People in Zijin County, Guangdong Province call it Douyou. "Notes on South Vietnam" mentioned that "one kind is as big as a bucket, and the pomelo fights every day", which is probably this species.

⒏ Sangma pomelo

The fruit is similar to Shatian pomelo, but the fruit base is narrow without neck or very short, the top of the fruit is flat, with obvious rings and radial grooves, the peel is rough, the oil cell is large, the core is slightly full, the flesh is tender, the water is rich, and it is sweet and sour. The fruit period is from mid-September to early October, and it is an early-maturing variety.

produced in all parts of Guangdong.

9

The fruit is oval, with round top, narrow and round base, small and dense oil cells, smooth peel, tender pulp, rich juice, sweet and sour taste, aroma and few seeds. The fruiting period is about November.

mainly produced in Zhejiang (Pingyang and other places).

(5) Liangping pomelo

The fruit is oblate and round, the top of the fruit is nearly flat, the base is slightly narrow and round, the peel is thin and smooth, quite tough, the oil cells are small and dense, the gourd ladle is of different sizes, the discharge is irregular, the pulp is yellowish white, soft, moist, sweet and sour, and has a special aroma. The fruiting period is November.

mainly produced in Chongqing (Liangping and other places).

(5) Late white pomelo

The fruit is oblate to spherical, with large calyx, flat to slightly concave and smooth peel. The oil cells are small and dense, and the flesh is yellowish white, tender, juicy, refreshing and fragrant. The fruiting period is December.

it is mainly produced in Taiwan Province, with a small amount planted in Fujian.

In addition, there are many good varieties and strains in various places, such as Madou Wendan, Baiyou and Douyou in Taiwan Province. Honey pomelo and Guanxi honey pomelo in Yunxiao, Fujian; Guangdong rouge foot mulberry pomelo, Siam pomelo; Pomegranate pomelo in Anjiang, Hunan, and chrysanthemum pomelo in Dayong; Dianjiang pomelo, Jintang pomelo, Wubu pomelo and Pengxi pomelo in Sichuan. ?

12. Crispy sweet pomelo

The fruit is oval or cone-shaped, with thin peel, fine oil cells and orange color; Crisp meat, aroma, good flavor, sweet pomelo fruit shape, high quality and high yield, early maturity and strong adaptability. The fruiting period is mid-October.

It mainly produces in Cangxi and Nanbu counties of Sichuan.

VII. Main application value

1. Edible grapefruit is very rich in nutritional value. It contains a lot of nutritional elements, including protein and organic acids needed by the body, and it also contains vitamins, calcium, phosphorus, magnesium and sodium and other trace elements necessary for the body.

2 nutritional efficacy

Modern medical research has found that pomelo meat is rich in vitamin C and insulin-like components, so it has the effects of lowering blood sugar, reducing blood fat, losing weight, beautifying skin and nourishing capacity. Regular consumption can help treat diseases such as hypertension, diabetes, arteriosclerosis, etc., and has the function of strengthening body and caring skin for obese people.

Grapefruit also has the functions of invigorating stomach, moistening lung, enriching blood, clearing intestine and facilitating defecation, which can promote wound healing and has a good auxiliary effect on septicemia.

3 Taboos

3.1 Edible: grapefruit is suitable for people with indigestion; Suitable for chronic bronchitis, cough, excessive phlegm and asthma; It is suitable for drinking too much, and eating grapefruit fresh after drinking can make the lips and teeth fragrant.

3.2 no food: because of its cool nature, people with qi deficiency and weakness should not eat more. Grapefruit has the effect of smoothing the intestines, so people with cold abdomen and frequent diarrhea should eat less.

3.3 Precautions

① Women who take birth control pills should avoid eating: an American study shows that grapefruit has the most prominent influence on birth control pills. Experts say, "If a woman who takes birth control pills eats one or two grapefruit after sex, or directly takes birth control pills with a large glass of grapefruit juice, then she may become a mother because grapefruit hinders women's absorption of birth control pills."

② people with deficiency and cold should not eat more: grapefruit is cold, and people with diarrhea due to spleen deficiency will have diarrhea, so people with deficiency and cold should not eat more.

③ Don't eat grapefruit when taking antihypertensive drugs: Experts advise not to eat grapefruit or drink grapefruit juice during taking antihypertensive drugs, otherwise serious side effects such as sudden drop in blood pressure may occur.

4 medicinal use

Chinese medicine believes that grapefruit is sweet, sour and cold in nature, and has the functions of invigorating the stomach, resolving food, reducing qi and eliminating phlegm, and being light and pleasing to the eye. Modern medical research has found that pomelo meat is very rich in vitamin C and insulin-like components, so it has the effects of lowering blood sugar, reducing blood fat, losing weight, beautifying skin and nourishing appearance. Regular consumption can help treat diseases such as hypertension, diabetes, arteriosclerosis, etc., and has the function of strengthening body and caring skin for obese people.