The latest growth characteristics of Rice and its requirements for Environment

In rice, seeds are usually germinated until new seeds are produced for a growth cycle of rice, that is, the growth period. Growth period can be divided into seedling stage, green stage, tillering stage, long ear stage (ear differentiation stage), seed setting stage. Generally, the seedling stage has been completed in the seedling field. After transplanting, the period of slow seedling survival is called the greening stage. After greening, tiller begins (some have begun tiller in the seedling field), and ear differentiation (jointing) begins. Before the young ear differentiation, it is the vegetative growth period dominated by long roots, stems and leaves. The reproductive growth period dominated by long ears, flowers and seeds from ear differentiation to maturity.

seedling stage

Seedling stage is the stage from seed germination to trifoliate stage, which is generally divided into seed germination stage and seedling growth stage. The temperature needed for seed soaking and germination is 12℃ for indica rice, 10℃ for stem rice, 30℃-32℃ for suitable temperature, and 40℃-42℃ for maximum temperature. However, the lowest temperature during seedling raising should not be lower than 5℃ or 0℃. First of all, seedling field should choose sunny, sheltered, irrigated, discharged and other field plots, such as low temperature can also be covered with film and other measures to avoid less rotten or not rotten. The temperature of emergence and seedling growth was 2℃ higher than germination, i.e. 14℃ for indica rice and 12℃ for stem rice.

Environmental Requirements of Rejuvenation Stage and Tillering

Rejuvenation period is the buffer period from seedling field to survival after transplanting, which is about 4 days. It is required to be shallow water. Because the water is too deep, the growth point (heart leaf) is submerged, the air permeability is not good, and the seedlings will rot, or the survival is slow. After rejuvenation, the vegetative growth period of roots and leaves will grow centering on tillers.

1. Temperature requirements. The optimum temperature for rice tillers was 30~32℃, and the optimum water temperature was 32 ~34℃. The highest temperature is 38℃~40℃, the highest water temperature is 40℃~42℃, the lowest temperature is 15℃~16℃, and the lowest water temperature is 16℃~17℃. Tillering is slower when the water temperature is below 22℃. Low temperature delayed tillering and affected the effective panicle number of total tillering, so it was required to start transplanting above 15℃.

2) Requirements for lighting. Sufficient sunlight is needed at tillering stage to increase photosynthetic intensity of leaves, produce organic matter, and promote increased tillering number. Under natural light, tillering begins 3 days after turning green. If only 50% natural light is used, tillering begins 13 days after turning green. If only 5% natural light is used, not only tillering will not occur, but even seedlings will die.

3. Water requirements. Tillering stage is the most sensitive period to water, but only water saturation of paddy field is required, or shallow water is most conducive to tillering. Under high temperature conditions (26℃~36℃), soil water holding capacity of 80% will produce the most tillering. Such as deep water irrigation, water layer more than 8 cm field, so that tiller node light weak, oxygen deficiency, low temperature and inhibit tiller. However, when the field is too dry and the water holding capacity is below 70%, it will stop tillering.

4. Nutritional requirements. Tillering needs more nutrition, and effective tillers are also more. Nutrients can promote tillering and growth faster and more. If nutrition is low, tillering is also low or stopped. Nitrogen, phosphorus and potassium are the main nutrients needed, especially nitrogen fertilizer. Best nitrogen, phosphorus, potassium topdressing with the most favorable.

Requirements of Jointing and Booting Stage to External Conditions

Jointing-booting stage is the period when vegetative growth and reproductive growth go hand in hand. At this stage, rice growth and development rapidly increase, root group reaches the maximum, leaf area of rice plant reaches the maximum, and at the same time rice panicle begins to differentiate. Jointing-booting stage is the key period to determine grain number per panicle, but also the consolidation period of effective panicle number per mu, and the decisive period of grain weight. The main factors lie in the influence of external conditions.

1. Nutrient requirements. In the process of young panicle differentiation, the root group of water root increased continuously, and the last three leaves grew out one after another. Both vegetative growth and reproductive growth needed nutrients. If there was lack of nutrients in this period, it would have adverse effects on young panicle differentiation. Therefore, it is necessary to carry out intertillage and topdressing in production, about 30~40 days before heading, in order to promote spikelet differentiation, increase the number of branches twice, this fertilizer can also be called "flower promotion fertilizer"; 10~20 days before heading, fertilizer can be sprayed once, that is, male and female flower core formation period and pollen mother cell meiosis period, fertilizer is most needed to prevent spikelet abortion, ensure more grains, this period topdressing is "flower protection fertilizer".

2. Temperature requirements. The suitable temperature for young panicle differentiation was 26℃~30℃, and 35℃ day and night was more favorable for large panicle formation. The external temperature for young panicle differentiation was 15℃~18℃, but the most sensitive stage was meiosis. During meiosis, both high and low temperatures can cause a large number of abortion and sterility of spikelets.

3. Light requirements. Light intensity is closely related to young panicle differentiation. Light intensity is beneficial to young panicle differentiation. It has been proved by experiments that spikelet degeneration is 30% more than that of control when two layers of sand cloth are used to shade young panicle differentiation (light transmission is about 1/6~1/8 of natural light). If cloudy and rainy days, less sunshine, too much closure, poor ventilation. Therefore, Guiyang has less light time, so it ensures reasonable rice density, promotes certain photosynthetic crops, and increases organic matter to grow rice with large ears and many grains.

4. Water requirements. From young panicle differentiation to heading, rice needs the most water in its life, especially at the meiosis stage of pollen mother cells, which is most sensitive to water demand. Therefore, it is necessary to keep the field water holding capacity above 90% at this stage. If water shortage affects the development of spikelet. However, excessive water flooding will also cause adverse effects, such as total flooding will also die.

Environmental requirements for heading and seed setting

In the heading and fruiting stage of rice, vegetative growth basically stops, this period is the main period of reproductive growth, all tasks are to maintain the key period of grain quantity and weight, mainly in the management to make rice not premature senescence, nor greedy green, not lodging.

1. Heading and flowering.

(1) Rice heading. 1~2 days after panicle differentiation, 50% of panicles were extracted from leaf sheath of flag leaf, which was heading stage, and 80% of panicles were extracted at full heading stage. Due to low temperature or insufficient fertilizer and water during heading, rice panicles are often unable to be fully extracted. This phenomenon is called "panicle wrapping" or "neck wrapping" in production. The wrapped grains cause blisters or empty shells. For example, when the temperature of hybrid rice heading is lower than 20℃, 100% of the panicles will be produced without harvest.

(2) Flowering; under normal circumstances, rice ears can bloom. Before flowering, the two plasmas in the glume absorb water first, and the volume expands 3~5 times. After sucking, the glume opens, and the angle of the glume and glume is about 25℃~30℃. The opening process is about 10~20 minutes. After full opening, the angle of 25℃~30℃ can be maintained for 30 minutes, so the whole flowering process is about 1~2 hours. Temperature has a great influence on flowering time, high temperature flowering time is short, low temperature flowering time is long, sometimes up to more than 2 hours. When the inner and outer glumes open, the filaments extend, the anthers dehisce, the pollen is scattered, the pollination is on the stigma, and the anthers wither slowly after about 10~15 minutes of pollination. At the same time, the size of the serous water decreases due to evaporation, and the inner and outer glumes close again.

2. Factors affecting the grain filling.

1) Light. Light intensity and light duration affect photosynthesis of rice leaves and the transportation of carbohydrates to grains. More than 90% of the substances filled in grains of high-yield rice are supplied by carbohydrates produced by leaf photosynthesis after heading. Therefore, photosynthesis at filling stage will directly affect rice yield.

(2) Temperature. Temperature is closely related to grain filling. Generally, the most suitable temperature for grain filling is 20℃~22℃. After 15 days before grain filling, the day temperature is 29℃, the night temperature is 19℃, and the daily average temperature is 24℃. For the next 15 days, the temperature should be 20℃ in the day, 16℃ at night and 18℃ in the day. Suitable filling temperature is beneficial to prolong the time of accumulating nutrients, slow aging of cells, less respiration and digestion, good rice quality. Both high temperature and low temperature are harmful to normal grain filling of rice and affect rice quality.

3) Water. Water content in filling stage is second only to water content in jointing stage, panicle stage and tillering stage. If water content is insufficient, it will affect leaf assimilation ability and transportation of filling substances, and insufficient filling will cause yield reduction. Water deficiency at grain filling stage will affect photosynthesis, reduce the efficiency of matter transport, shorten the time, and deteriorate the physical characteristics of rice.

(4) Mineral nutrition. There is a close relationship between leaf nitrogen content and photosynthetic capacity during grain filling period. Appropriate nitrogen application can increase photosynthesis of leaf area, maintain maximum leaf area, prevent premature senescence, improve root activity, and greatly affect rice yield. Therefore, topdressing methods outside roots are often used in production. In the full heading stage, it can be seen that the seedlings are supplemented with fertilizer, or phosphorus and potassium fertilizers, etc., to ensure that the filling process can be carried out normally.

Factors Affecting Rice Root Growth

1. Temperature

The optimum soil temperature for rice root growth was 30℃~32℃. The growth is inhibited above 35℃, the aging is accelerated, and the absorption capacity decreases; the decline is significant above 37℃; the growth and absorption capacity are greatly weakened below 15℃; and the growth stops below 10℃.

2. Light

Light plays an indirect role in root development and absorption capacity. Because sufficient light strengthens photosynthesis and transpiration, the nutrients supplied to the roots increase, so it promotes the development of the roots, improves the vitality of the roots, and increases the absorption of inorganic nutrients by the roots. When the light is insufficient, it not only affects the development of roots, but also makes the absorption of various inorganic nutrients by roots decrease obviously.

3. Soil nutrients

Among the three elements of fertilizer, nitrogen had the greatest effect on root growth and absorption capacity. Appropriate nitrogen fertilizer can effectively increase the differentiation of root primordia and the rooting ability of rice plants, increase the number of roots per plant and shorten the root length. Nitrogen deficiency or excessive nitrogen supply, roots are small. Combined application of phosphorus and potassium fertilizer promoted root growth more greatly, increasing root number, root quantity and root length, and deepening root distribution.

4. Soil aeration

Rice root growth, elongation and nutrient absorption, transformation and other physiological activities, there must be enough oxygen. If oxygen deficiency affects root growth and physiological function, root activity will also be lost.