Chinese name: citrus fruit tree kingdom: plant kingdom: dicotyledonous plants order: Sapindaceae: Rutaceae genus: citrus morphological characteristics, growth environment, distribution range, main species, cultivation techniques and morphological characteristics. Rootless roots propagated by layering or cutting. When the soil conditions are good, the lateral roots are numerous and widely distributed, and mycorrhiza often occurs. Fine roots on lateral roots have strong regeneration ability, and roots exposed on the soil surface are easy to take root and tiller. Many species and varieties have needles on their branches. Buds are compound buds. Generally, one leaf axil germinates new buds, and the rest are dormant. When the new shoots stop growing, the terminal buds will wither, which is a unique "self-shearing" phenomenon of citrus fruit trees. At this time, a lateral bud at the top replaces the terminal bud, so the branches are often twisted. Ungerminated buds can maintain their germination ability for many years. This characteristic is often used in production to repair the broken crown or renew the old tree through the germination of * * * hidden buds. Compound leaf, consisting of three leaflets, or "single leaf compound leaf". Citrus and kumquat are evergreen trees, except Fructus Aurantii, which is deciduous. Fully flowering, fragrant, with developed nectaries. There are single flowers and inflorescences. The phenomenon of flower organ hypoplasia is common, and it is easy to bear fruits with few stones or no seeds. Sometimes parthenocarpy. There is an obvious dormancy period of Fructus Aurantii in winter, and kumquat and citrus grow almost every year. Generally, bamboo shoots are picked 3-4 times a year. Spring shoots are relatively neat, with the largest number, and some of them are fruiting branches of the year; Summer shoot is the main branch of young tree crown; Autumn shoots are mostly mother branches that bear fruit in the following year. On the basis of spring shoots, two or three buds can be regenerated. Winter buds are meaningless in production and should be erased as soon as possible. Most species bloom/kloc-0 times a year in spring, but lemon and citron can blossom and bear fruit all year round. Kumquat blooms continuously for 2-3 times every other month from June to July, and each flower can bear fruit. The number of citrus blossoms is large, but the fruit setting rate is not high. Generally, self-pollination is used for fertilization, but Shatian pomelo needs cross-pollination to improve its yield. It takes 6 ~ 14 months from flower withering to fruit ripening, which varies from species to species. The fruit is developed from syncarp, and the meat is pulpy, so it is called "citrus fruit". The exocarp and mesocarp are close together to form a tough pericarp, and the exocarp contains many oil cells; The mesocarp is spongy, and the boundary between mesocarp and exocarp is difficult to distinguish. Endocarp forms sacs (i.e. locules), also known as pulp sacs, with spindle-shaped juicy protrusions embedded in them, called juice cells, which are the main edible parts of citrus (see figure). Seeds are usually polyembryonic, with only one sexual embryo, and the rest are unfertilized asexual embryos produced by nucellar cells, called nucellar embryos; Some species are monogamous. When multi-embryo seeds germinate, sexual embryos are often aborted, and seedlings are mostly developed from asexual embryos, which can maintain the basic characteristics of the mother variety, but it also brings difficulties to cross breeding. The chromosome number is generally 2 n = 18. Interspecies and genera are easy to hybridize, and branches and buds are easy to mutate (bud change). Grafting compatibility is generally good, and it is possible to provide a variety of rootstock and scion combinations to meet the needs of production or other special purposes. Growing environment Citrus plants originated in subtropical areas with high temperature and high humidity. The area where the annual average temperature is above 15℃ and the extreme low temperature is not lower than -7℃ is suitable for growing citrus. The areas with annual temperature above 17℃ and extreme low temperature not lower than -5℃ are suitable for planting citrus and grapefruit. Lemon and citron are suitable for areas with extreme low temperature not lower than -3℃. Citrus grandis and kumquat are native to continental climate zone and have strong cold tolerance. Kumquat can be planted in almost all places suitable for citrus production. Fructus Aurantii can withstand the low temperature of -23℃. Generally, germination begins when the average daily temperature reaches 65438 03℃, and the optimum growth temperature is 23 ~ 365438 0℃, which weakens at 37℃ and stops at 39℃. Citrus requires annual rainfall 1000 ~ 1200mm, which is evenly distributed. The requirements for soil are not strict, and the neutral to slightly acidic (pH 5.5 ~ 7.5) with deep soil layer and good drainage and air permeability is the best. Strong winds are not conducive to the growth and fruiting of citrus. Distribution Most of the important citrus varieties in the world originated in China. Two important species, Fructus Aurantii and Kumquat, are native to central and south-central China respectively. There are many kinds of citrus, which are distributed in the southern half of Asia and parts of Oceania, mainly in southern China and zhina, India, and to the northeast of India in the west. At present, the cultivation areas are distributed in tropical and subtropical areas between 40 north latitude and 40 south latitude, and the altitude is below 1000 meters; Economic cultivation is concentrated between 20 and 33 north latitude, and citrus is produced in more than 90 countries. In the order of output, the main producing countries are Brazil, the United States, Japan, Italy, Spain, Mexico, India, Israel, Argentina, Egypt, Turkey, China, Morocco and Greece. Citrus in China is distributed between north latitude18 and 37, including 20 provinces (autonomous regions); Economic planting areas are concentrated in Sichuan, Taiwan Province, Guangdong, Guangxi, Fujian, Zhejiang, Jiangxi, Hunan, Hubei, Guizhou, Yunnan 1 1 province (autonomous region). The cultivation and utilization of citrus and grapefruit are recorded in Shangshu of Gong Yu, China. Citrus seeds were found in the Western Han Tomb of Mawangdui in Changsha. After the Zhou and Qin Dynasties, economic cultivation appeared in patches. As for the names of citrus fruit trees, they have appeared in ancient books in China, such as "orange", "pomelo", "orange" and "orange". In the early days, it was often used with "pomelo" to refer to citrus fruit trees. "Orange" and "orange" appeared together in the local customs annals of the 3rd century. Since then, with the development of cultivation and in-depth observation, the differences of characters among different varieties have been more and more recognized. The names of oranges, pomelo, tangerine and orange are all preceded by various adjectives, such as "pig liver" and "milk orange" found in herbs (8th century AD). The book also distinguishes oranges from oranges. Grapefruit is recorded separately. In the Southern Song Dynasty, Han Yanzhi wrote The Record of Oranges, which listed as many as 27 citrus varieties, and was the first complete monograph on citrus in the world. In foreign countries, citrus fruit trees were introduced to Europe and America from their origin, which was late. Citron was first known to westerners. In about 330 BC, Citron spread to the Mediterranean coast through Iran. Then lemon was introduced into the Mediterranean region of Europe in the 1 1 to 12 century. Sweet orange was introduced to Europe from the south of China by the Portuguese in the early15th century, then brought to Haiti by Columbus in 1493, and then spread to the West Indies. 65438+ was introduced to Mexico and the United States in the early and middle 4th century, and gradually became the main citrus fruit tree cultivated in the United States. Citrus was introduced to the west late,/kloc-0 was introduced to Britain from China in 805, and/kloc-0 was introduced to kumquat from China in 846. However, citrus fruit trees developed rapidly after being introduced into Europe and America. At the end of 19, the global annual output of citrus was less than10 million tons, and the average annual output increased from 1945 to12.39 million tons, reaching10/280,000 tons in 1985. Among them, sweet orange accounts for the largest proportion. There is only one main variety, namely, orange, also known as dried tangerine peel. Deciduous shrubs or small trees have small fruits, rich in gum, sour and bitter, and cannot be eaten. After drying, it is called medicinal Fructus Aurantii. Mainly used as rootstocks, or hedges and ornamental trees. China reaches Shandong, Henan, Shaanxi and Gansu in the north and Hainan Island in the south. Countries all over the world are also widely introduced and utilized. Another hybrid with sweet orange, commonly known as orange, is also an important citrus rootstock. Kumquat is an evergreen shrub or small tree. There are 4 species in this genus: ① Kumquat. There are also famous golden beans and kumquat. China, Guangdong, Guangxi, Fujian, Zhejiang, Hunan, Jiangxi and other mountainous areas are all wild. Fruits such as soybeans are round or oblate, with few juice cells, sweet and sour, and it is unbearable to eat them raw. 2 F. margarita. Also known as jujube, milk kumquat, jujube orange, etc. Cultivated in various producing areas of China, the fruit is oblong or obovate, with sweet skin and sour pulp, which can be eaten raw or pickled or ornamental. (3) Japanese kumquat (F.japonica), also known as kumquat, is cultivated all over the Yangtze River basin. The fruit is as small as cherry, round and loose, and the whole fruit can be eaten or made into candied fruit. Trees are available for viewing. ④ Rhodiola multiflora, cultivated in the eastern coast of Guangdong and Hainan Province. The leaves are lanceolate and winged, the fruit is spherical, the skin is thin and there are many large oil cells. There are two other hybrids in this genus: ① golden bullet. Also known as kumquat. China's Zhejiang, Guangxi, Jiangxi, Hunan, Fujian, Guangdong and other provinces (autonomous regions) are relatively concentrated in cultivation, which is one of the varieties with the highest economic value in kumquat. The fruit is oval or nearly spherical, with sweet skin and meat, good raw food and dense preserves. It is generally considered to be a hybrid of kumquat and Luofu. ② Yue Yue Orange. Also known as Four Seasons Orange and Longevity Orange. The fruit is sour and fragrant, it can blossom and bear fruit every month, and the size coexists, hence the name. More is ornamental cultivation. Citrus potted citrus evergreen trees or shrubs. Citrus fruit trees are the most important genus, with a wide variety and complex varieties. Scholars in different countries have different views on classification. 1960, China scholar Zeng Mian put forward the opinions of 32 major species. In fact, there are about 10 species with important economic status, such as citron (Citrus medica), lemon (C.limon), lemon (C.aurantifolia), lime (C.aurantium), sweet orange (C.sinensis) (see orange) and pomelo (C. Do you have any rootstocks, such as bitter orange, lime and red? Lemon, red orange, doghead orange, sweet orange, sour pomelo (such as pomelo anvil), etc. When building gardens on hillsides and hills, it is necessary to build soil and water conservation facilities such as terraces, add deep ploughing layers, apply organic fertilizers and improve garden soil. It is better to plant seedlings in spring and autumn, and transplanting with soil is beneficial to survival. Young orchards should be watered and fertilized frequently. Adopt short stem and natural round head shape for plastic surgery. Intercropping green manure and deep ploughing can increase soil organic matter content, improve citrus soil structure, and be beneficial to water storage and moisture conservation. Results Pre-flowering fertilizer, fruit stabilizing fertilizer, strong fruit fertilizer and pre-harvest fertilizer are the most important fertilizers for trees. In addition to nitrogen, phosphorus and potassium, it is necessary to increase the lack of trace element fertilizers according to soil analysis. Results The pruning of trees should be light, and the combination of thinning should be adopted (see fruit tree pruning). The relationship between vegetative growth and fruiting can also be adjusted by wiping buds (erasing unnecessary summer buds) and releasing buds (promoting hair growth and retaining needed autumn buds). The fruit picking time is determined according to maturity and use. Diseases, insects, mites and scale insects are common pests with great influence. Canker disease is the main quarantine object and widely distributed. Huanglongbing is a devastating disease in southern China. In order to prevent and control pests and diseases, it is necessary to strictly implement the plant quarantine system, cultivate disease-free seedlings, implement isolated planting and eliminate disease vectors. In addition, freezing injury often poses a serious threat to the middle and lower reaches of the Yangtze River in China. In addition to choosing suitable environmental conditions and varieties with strong cold resistance, various anti-freezing measures can also reduce the losses caused by periodic frost in garden construction.