How to grow rice?

Rice is one of the most important food crops in China. China's rice planting area accounts for about 30% of the grain crop area, and the output is close to half of the total grain output.

Growth and development of rice

First of all, the life span of rice

(1) The whole life of rice can be divided into two periods: vegetative growth and reproductive growth. From seed germination to young spike differentiation, roots, stems and leaves grow during this period, which is called vegetative growth period; Young panicle differentiation to heading, young panicle stem and leaf grow at the same time, which is a period of simultaneous vegetative growth and reproductive growth. The grain filling and fruiting period after heading, flowering and pollination is called reproductive growth period; There are interrelated and restrictive relationships between different growth periods. Coordinating the relationship between vegetative growth and reproductive growth is one of the important principles of high-yield cultivation of rice.

1. The growth period of rice is called the growth period from emergence to maturity.

2. The growth stage of rice

Every development stage of temperature-sensitive rice has been completed; The biochemical reaction required for qualitative change of growing point and the total heat required for plant growth are the least. This total heat is expressed by effective accumulated temperature, active accumulated temperature and total accumulated temperature. Different types of rice varieties have certain requirements for accumulated temperature, and it is quite stable. Different varieties have different requirements for accumulated temperature, but there is little difference between varieties in reproductive growth period, mainly in vegetative growth period. Late-maturing varieties have more accumulated temperature to meet the requirements of vegetative growth. The accumulated temperature required for each growth period of rice is stable, so when the temperature rises, the time to reach the required accumulated temperature becomes shorter and the growth period becomes shorter. When the temperature decreases, the time to reach the required accumulated temperature becomes longer and the growth period is prolonged. This is the temperature sensitivity of rice, also known as the temperature sensitive period.

(2) Photosensitive rice is a short-day crop, and its induction of flowering is mainly in the long dark period. In order to cause the qualitative change of growing point from vegetative growth to reproductive growth, it must exceed a certain critical dark period. The light was shortened, the dark period was prolonged, the photoperiodic induction was completed quickly, and the young panicle differentiated early. Light prolonged, dark period shortened, photoperiodic induction completed slowly, and young panicle differentiation was delayed. This is the photosensitivity of rice, also known as the photoperiod. Different varieties have different photosensitivity, less days of early maturity and more days of late maturity.

(II) Formation of Rice Yield Rice yield consists of three factors: number of panicles per unit area, number of grains set per panicle and dry grain weight. These three factors are formed in different growth periods.

1. The number of spikes per unit area consists of the number of plants, the number of tillers per plant and the tillering rate. The number of plants depends on the transplanting density and survival rate, and the transplanting density and survival rate are based on the seedling stage. Therefore, only by cultivating seedlings well and strengthening the quality of seedlings can we ensure that seedlings turn green quickly, tiller early and have more ears after transplanting. The key period to determine the number of spikes per unit area is tillering stage. On the basis of strong seedlings and reasonable close planting, the number of panicles per mu depends on the number of tillers per plant and tillering rate. The earlier tillers are born, the greater the possibility of panicle formation. Late tillers are not easy to ear. Therefore, actively promoting early tillering and properly controlling late tillering are the basic requirements of rice cultivation at tillering stage.

2. The key period of grain number per panicle formation is long panicle stage. The panicle size and grain number mainly depend on the number of spikelets formed during the differentiation of young panicles and the spikelet setting rate. In the process of spikelet formation, if the nutrients can't keep up, the development will often stop halfway, forming abortive spikelets, reducing the seed setting rate and leading to the decrease of spikelets. The basic requirement of long spike cultivation is to cultivate strong stalks and big spikes to prevent spikelets from aborting.

3. The formation of grain weight determines the grain weight and final yield during grain filling. The grain weight of rice consists of grain size and maturity. The grain size is restricted by the size of chaff, and the maturity depends on the accumulation of grain filling materials. The accumulation of substances in seeds mainly depends on the accumulation of photosynthetic products during this period. If rice is premature aging or greedy for green growth, as well as adverse climatic factors, it will not be well filled, affecting maturity, causing empty grains, reducing grain weight and affecting yield. Therefore, promoting big grain fullness and preventing empty grains are the basic requirements of cultivation at filling stage. The above three yield factors are mutually restricted in the process of rice growth and development. Generally, when the number of spikes per mu exceeds a certain range, the number of grains per spike and grain weight tend to decrease with the increase of spikes. Therefore, high yield of rice is the unity of contradiction and opposition among panicle number, grain number and grain weight. Its essence is the contradiction and unity of opposites between groups and individuals.

Second, the growth and development of rice seedlings The period when rice grows in the seedling field is called seedling stage. Seedling growth can be divided into rice seed germination and seedling growth.

(1) Shading of rice seeds The growth of rice begins with seed germination. When rice seeds absorb water and swell, radicle breaks through the seed shell and exposes white spots, it is called "exposing white" or "breaking chest"; Germination occurs when the radicle reaches the length of the seed or when the germ reaches half the length of the seed. The conditions for seed germination are as follows.

1. Moisture Rice seeds need to absorb enough water first. When the water absorption of seeds reaches 25% of their own weight, they begin to germinate. The water absorption rate is related to the water temperature. High water temperature absorbs water quickly, while low water temperature absorbs water slowly.

2. Temperature The lowest temperature for rice germination is 65438 00℃, and the optimum temperature for japonica rice germination is 20-25℃, so the germination is neat and robust. The maximum temperature is 40℃. Therefore, the germination temperature of rice is required to be kept at 30-35℃, and then decreased to 20-25℃ after the breast is broken, so as to promote the vigorous growth of root buds.

3. Air rice seeds can germinate under the oxygen-free water layer, but this germination is abnormal, often the buds grow fast and the roots grow slowly. Because rice seeds can germinate only when oxygen is inhaled and enough energy is obtained. When rice germinates normally, it draws oxygen from the air to breathe, which is called aerobic respiration; When lacking oxygen, it obtains oxygen from seed organic matter to breathe, which is called anaerobic respiration. Therefore, in the case of normal germination, rice seeds grow roots first and then buds, and vice versa.

② Growth characteristics of seedlings

1. When rice seeds growing above the ground germinate and emerge, the bud sheath wrapped outside the bud first extends out of the ground and becomes a sheath leaf. This kind of leaf is tubular, with no leaves and no chlorophyll. When the bud sheath extends to a certain extent, L leaves are extracted from it, and the green color is small, only the leaf sheath is seen, which is called incomplete leaves. When this leaf is about 1 cm long, the seedling field appears green, which is called emergence or greening. After that, L leaves will grow every 2-3 days, with leaves and leaf sheaths, which are called complete leaves. When the third complete leaf unfolds, it is called "trilobal stage". At this time, the nutrients in the endosperm of the seed are exhausted and the seedlings enter an independent life, so it is called "weaning period".

2. When the rice seeds growing underground germinate, they first extend downward from the radicle and grow into seed roots, which are vertically stuck in the soil like nails. When seeds germinate and emerge, they mainly rely on it to absorb water and nutrients. Then, the roots begin to grow on the bud node, which usually has five roots. At first, two plants grew, and after 1-2 days, two plants grew in symmetrical positions, and then L plants grew like chicken feet. In the early stage of seedling growth, that is, from the stage of leaf release to the stage of leaf center, seedlings are mainly formed by this root. After three leaves, roots grow from incomplete leaves and complete leaves in turn, which are collectively called "nodal roots" It's strong and has ventilation tissue. Therefore, after three leaves, the water layer can always remain in the seedling field.

3. Requirements of seedling growth period on environmental conditions

(1) temperature requires that the minimum temperature for japonica rice to emerge is 65438 02℃, and that for indica rice is 65438 04℃. Under this temperature condition, the emergence rate is low and the speed is slow. The average daily temperature after emergence is about 20℃, which is most conducive to cultivating strong seedlings. Too high or too low is not good. If the low temperature reaches 5-7℃, it is necessary to keep warm, otherwise the rice fungus will be frozen.

(2) The air requires the seedling field to have enough oxygen to grow normally. Seedlings grow poorly under flooding, with few roots and weak seedlings. Especially before the three-leaf stage, flood irrigation is not conducive to cultivating strong seedlings. Therefore, in the process of seedling cultivation in seedling field, small amount of irrigation is beneficial to cultivate strong seedlings. Wet seedling raising and dry seedling raising are aimed at cultivating strong seedlings and meeting the requirements of oxygen for seedling growth.

(3) Water requirement The water requirement of nursery field increases with the growth of seedlings. Before emergence, only 40%-50% of the maximum field storage capacity can meet the needs of germination and emergence. No water layer is needed before the three-leaf stage, and the soil water content is 70% on the left and 70% on the right. After the third stage, the soil moisture is not lower than 80%, which will affect the growth of rice.

(4) Light needs light, and light is one of the important conditions for cultivating strong seedlings. Because of the abundant sunshine, seedlings can use carbon dioxide and water in the air and nutrients absorbed by roots to synthesize organic matter through photosynthesis for growth and development.

Third, the growth and development of tillering stage

Tiller growth

1. The law of tillering occurrence There are several dense stem nodes at the base of the main stem of rice called tillering nodes. L Leaves grow on each node, and there are 1 tiller buds in the axils of leaves, which grow into tillers. The leaf position of tillering is called tillering position. All tillers that grow directly from the main stem are called primary tillers, those that grow from primary tillers are called secondary tillers, and those that grow from secondary tillers are called tertiary tillers. And so on. Tillering occurs at the bottom-up nodes of the main stem. Generally speaking, tillers always appear three leaves away from the mother stem. N leaf extension = n- The first leaf of three-leaf tiller appears.

2. Factors affecting tillering

(l) The occurrence of tillering is related to the nutritional status of seedlings, especially nitrogen nutrition plays a leading role. At seedling stage, most tillering buds on the basal nodes are dormant because of too dense sowing and insufficient nutrients and light. After jointing, the growth center deviates, and the tillering buds on the upper nodes also lurk and do not germinate. Therefore, only the tillering nodes in the middle section can develop, but this is also related to other factors.

(2) The optimum temperature for tillering growth is 30-32℃, and it is not conducive to tillering growth if it is lower than 20℃ or higher than 37℃, and it will stop growing if it is lower than 16℃.

(3) Tillering is related to light. Under natural light, tillering began 3 days after turning green, and started at 13 days when the light intensity was 50% of natural light. When the light intensity drops to 5% of the natural light intensity, tillering will not occur and the main stem will die.

(4) The occurrence of tillering is related to water content, and sufficient water is needed during tillering. When there is water shortage or water shortage, the physiological function of plants will decline, and the nutrient supply of tillers will be insufficient, which will often dry up and die. This is the truth that "Huang Miao is released until she is old". In addition, tillering is also related to variety characteristics, and there are differences in tillering ability among different varieties. Tillering in this field experienced a process from slow to fast, and then from fast to slow. When 10% seedlings tiller in the whole field, it is called early tillering stage. The time when tillers grow fastest is called tillering peak period. When the total number of stems in the whole field is equal to the last panicle number, it is called the effective tillering termination period. Hereinafter referred to as ineffective tillering stage. When the number of tillers in the whole field reaches the maximum, it is called the highest tillering stage.

(2) Leaf growth The growth of rice leaves, the first three leaves are born before tillering, the last three leaves grow at long panicle stage, and the rest grow at tillering stage. The number of main stems and leaves of rice varies with varieties. Generally, the main stems of early-maturing varieties have 12- 13 leaves, middle-maturing varieties have 14- 15 leaves, and late-maturing varieties have 16- 19 leaves. With the growth of three leaves before tillering, L leaves grow every three days or so. Leaf growth at tillering stage, once every 5 days. Leaf growth after jointing, L leaves once every 7-9 days. The size and length of leaves are different. The inverted 4 leaves of middle mature species are the longest, and the inverted 3 leaves of early mature species are the longest. The life span of leaves is different. The life span of L-3 leaves is only 10-20 days at early birth. In the later stage, with the increase of leaf position, the life span gradually increased, and the life span of flag leaf was the longest, reaching about 50-60 days.

(3) The tillering stage of root growth is also the main stage of root growth. Any root that grows from the stem node is called the first root, the branch root that grows on the first root is called the second root or the first branch, and the third root and the fourth root can grow later. All nodes of rice have the ability to take root. With the birth of leaves, they take root one section at a time. Generally, the difference between hairy roots and leaves is 3 knots, and the appearance of branched roots decreases by one knot in turn. There are aeration tissues in the roots of rice, which are connected with similar tissues in stems and leaves, and become a way to transport oxygen from the aboveground parts to the roots, so that rice can still grow under the condition of flooding and hypoxia. The development of rice root system is closely related to water, fertilizer, gas and heat in soil. For example, the optimum temperature for rice root growth is 28-30℃. Above 35℃, the growth is hindered, below 15℃, the growth is weakened, and below 10℃, the growth stops.

4. Long panicle stage (from jointing to heading) When rice grows to the end of tillering, it begins to elongate the internodes of the stem (jointing) and differentiate the young panicles until the elongation of the internodes is completed, and the young panicles grow to the panicles, which is called the long panicle stage. During this period, the vegetative growth and reproduction of rice went hand in hand, on the one hand, the growth and development of vegetative organs such as roots, stems and leaves were completed, and at the same time, the young panicles differentiated and developed to form reproductive organs.

Growth of roots and leaves

1. Root growth Rice grows adventitious roots from all nodes at tillering stage, and only the upper nodes continue to grow adventitious roots at jointing stage, mainly from adventitious roots. This root is deeply rooted. At the heading stage, the root distribution was inverted oval. The total root amount reached the peak.

2. The growth of stems After rice jointing, several internodes above the ground elongate and become obviously visible stems. Different varieties have different elongation nodes. Early-maturing varieties have 3-4 elongation nodes, middle-maturing varieties have 5-6 elongation nodes, and late-maturing varieties have 6-7 elongation nodes. The elongation of internodes is carried out one by one from bottom to top. Therefore, the management of several basal internodes can be strengthened at jointing stage to make them short and strong, lodging resistant and high yield.

3. Growth of leaves After rice enters the jointing stage at the end of tillering, the leaves grow from L leaves of about 5 days to every 7-9 days 1 leaf; The life span is also prolonged, and the leaves at the ear stage reach more than 40 days; The division of labor in leaf layer is obvious. The nutrients produced by the upper leaves are mainly transported to the young spikes in the growth center, while the nutrients produced by the lower leaves are mainly used for the growth of internodes and roots. Leaf area and population should be suitable. If the line is closed too early, it will affect the stubbornness of stems and internodes, premature root senescence and poor results. Too late closure, too small leaf area, and less nutrient production and accumulation will also affect strong stalks and big spikes. Generally, it is more appropriate to master the tip of the sword leaf.

(2) Young panicles differentiate into panicles of Oryza, with a main stem called panicle axis, a node on the panicle axis called panicle node, and the last node called panicle neck node. There are long branches on the ear nodes, which are called primary branches. Re-branching a long secondary branch. Branchlets grow from primary and secondary branches, and spikelets (flowers) are born at the ends. The process of panicle differentiation of rice can be divided into several periods with different strokes. Here are more concise strokes.

1. The branching differentiation stage includes three stages: the first bud primordium differentiation, the first branching differentiation and the second branching differentiation. The differentiation stage of the first bud primordium refers to the formation of an annular protrusion above the base of the growth cone and the base of the sword, which is the first bud primordium. This is a sign of young spike differentiation. In the first branching and differentiation stage, the growth cone expands and horizontal stripes appear; From bottom to top, the primary branch primordium process was differentiated, and the first bud grew a white bud, indicating that the primary branch differentiation was terminated. In the stage of secondary branching and differentiation, secondary branching primordium processes appear on both sides of the primary branching primordium, and the order is opposite to that of the primary branching, proceeding from top to bottom. At the end of secondary branch differentiation, all young panicles are covered by bracts. The young spike is 0.5- 1.0 mm long.

2. The spikelet differentiation stage includes two stages: spikelet primordium differentiation and pistil formation. The initial stage of spikelet differentiation is glume protection and when the exoglume primordium of the lower floret appears at the top of the upper primary branch. And then differentiate into internal and external glume groups. When the pistil primordium appears, it enters the stage of pistil formation. The order of differentiation develops from top to bottom. Spikelets at the top of branches differentiate first, and then differentiate upward from the base.

3. The meiosis stage includes two stages: the formation of pollen mother cells and the meiosis of pollen mother cells. That is, the development and enrichment, meiosis and tetrad formation of pollen mother cells from anthers. Spikelets develop into effective and degenerated poles, and degenerated spikelets stay in the pistil formation stage and become abortive spikelets or spikelets.

4. In the completion stage of pollen enrichment, the panicle length is fixed and the spikelets reach the full length, mainly because the pollen grains are enriched, the pollen turns yellow, the inner and outer glumes all turn green, the male and female spores all mature, and the rice plants begin to head and blossom.

(3) Field identification of young spike differentiation.

1. According to the perennial heading date, it is inferred that the young ear begins to differentiate about 30-35 days before heading, the secondary branch differentiation about 20-25 days before heading, and the meiosis period about 10- 15 days before heading. It varies with varieties, regions and cultivation conditions.

2. According to the jointing situation, spikelets began to differentiate when the fifth internode was extended from top to bottom, spikelets differentiated when the fourth internode was extended, meiosis occurred when the third internode was extended, and pollen grains formed and entered the heading stage when the second internode was extended.

3. According to the length of spikelets and spikelets, when the spikelets are 0.5- 1.0 mm long and covered by bracts, it is the second branching and differentiation stage. The pistil formation period is when the young spike is 5- 10 mm long. When the young spike length is 1.5-4.0 cm, it is the pollen mother cell formation period. When the young spike and spikelet reach about half of the total length, it is meiosis. When the young spike and spikelet are close to the full length, it is the completion period of pollen content enrichment.

Verb (abbreviation of verb) The growth and development of rice during grain filling period is called grain filling period. This process takes about 30-55 days, and the days of different varieties are different.

(1) The young panicle of flowering and fertilization rice protrudes from the sheath of flag leaf, which is called heading. It takes about 3-5 days to extract all ears. When half of the leaf sheaths of rice plants in the whole field 10% are drawn out, it is heading stage. There are 50% plants heading, which is the heading stage. When there is 80% heading, it is the full heading stage. The spikelet at the top of the spike will bloom after leaving the flag leaf sheath 1-2 days. The order of flowering is the same as that of spikelet development. As far as one ear is concerned, from top to bottom. As far as a branch is concerned, it starts from the top and then goes from the bottom to the top. After each flower opens, cracks, scatters pollen and pollinates itself, the anther spits out glume. Each flower from opening to closing is 1-2 hours. Generally speaking, flowers bloom from 9: 00 a.m. to 10 a.m., at1-12 a.m. and stop at 2-3 p.m. ... The optimum temperature for flowering is 30-35℃, and the lowest temperature is 65438 05℃. It takes about 5-8 days for an ear to blossom. After pollination, the pollen germinates for about 2-7 minutes, extends out of the pollen tube, enters the ovary along the stigma, reaches the ovule, drills into the micropyle and enters the embryo sac for about 30 minutes. The tip of pollen tube breaks, releasing two male nuclei, and one male nucleus fuses with two polar nuclei to form a large nucleus, that is, embryonic milk pronucleus. A male nucleus enters an egg for fertilization, and the fertilized egg will develop into an embryo in the future. Generally, the fertilization process is completed in 9- 18 hours after flowering.

② Grouting is firm.

1. The ovary began to elongate on 1 day after fertilization, and the rice grain reached its maximum length on the 6th to 7th day after flowering. At this time, all the organs of the embryo are basically completed and begin to germinate. After 8- 10 days, the rice grains reached the maximum thickness. The fresh weight of rice increased fastest in 10 day after anthesis, and reached the maximum in 25-28 days. The increase of rice grain dry weight reached its peak at 15-20 days after anthesis and reached its maximum at 25-45 days after anthesis.

2. Grain maturity Rice grain maturity is generally divided into milk maturity, wax maturity and complete maturity. Generally, it enters the milk ripening stage 3-5 days after flowering, when the starch deposits in the seeds are milky white. On this basis, the white emulsion thickens until it becomes waxy and the chaff turns yellow, which is called wax ripening period. When the wax matures for about 7-8 days, it enters the mature stage. At this time, the rice grains are hard and strong, and the back is blue and white, and the life of rice is over.

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