Growth characteristics of Rice and its requirements for Environment

On rice, seeds are usually germinated until new seeds are produced as a growth cycle of rice, that is, the growth period. The growth period can be divided into seedling stage, green stage, tillering stage, long panicle stage (panicle differentiation stage) and fruiting stage. Generally speaking, the seedling stage has been completed in the seedling field, and the period of slow seedling survival after transplanting is called the green stage, and after turning green, it begins to tiller (some have already started tillering in the seedling field), and the panicle differentiation (jointing) begins. Before the young panicle differentiation, it is the vegetative growth period of long root, stem and leaf, and the reproductive growth period of long spike, flower, grain and so on.

Seedling stage

The seedling stage is the stage from seed germination to clover stage, which is generally divided into seed germination stage and seedling growth stage. The temperature required for seed soaking and germination is 12 ℃ for rice, 10 ℃ for stem rice, the optimum temperature is 30 ℃-32 ℃, and the highest temperature can reach 40 ℃-42 ℃, but the lowest temperature should not be less than 5 ℃ or 0 ℃ during seedling raising. Rotten seeds, rotten buds and rotten seedlings will occur at low temperature. First of all, the seedling field should choose sunny, wind shelter, water irrigation, discharge and other fields, such as low temperature can also be covered with film and other measures to avoid less rotten or not rotten. The temperature of seedling emergence and seedling growth was 2 ℃ higher than that of germination, that is, 14 ℃ for rice, 12 ℃ for stem rice, and more than 16 ℃ for stem rice.

The Environmental requirements of returning to Youth and Tillering

The period of returning to green is after transplanting, the buffer period for survival from seedling field to Honda is about 4 days, the requirement is shallow water, because the water is too deep, the growing point (heart leaf) is submerged, the permeability is not good, the seedling will rot, or the survival is slow, and then take tillering as the center, the vegetative growth period of roots and leaves.

1. Temperature requirements. The optimum temperature of rice tillering is 3032 ℃, and the optimum water temperature is 32 ℃ ~ 34 ℃. The highest temperature is 38 ℃ ~ 40 ℃, the maximum water temperature is 40 ℃ ~ 42 ℃, the minimum temperature is 15 ℃ ~ 16 ℃, and the lowest water temperature is 16 ℃ ~ 17 ℃. The tiller is slower when the water temperature is below 22 ℃. Low temperature delayed tillering and affected the effective panicle number of total tillers, so it was required to start transplanting seedlings above 15 ℃.

2. The requirement of light. Sufficient sunlight is needed at the tillering stage to improve the photosynthetic rate of leaves, produce organic matter and increase the number of tillers. Under natural light, tillering begins 3 days after turning green. If only 50% natural light, 13 days after turning green, tillering begins. If there is only 5% natural light, not only tillers will not be produced, but even seedlings will die.

3. Water requirement. The tillering stage is the most sensitive to water, but only the paddy field is saturated, or shallow water is the most favorable for tillering. Under the condition of high temperature (26 ℃ ~ 36 ℃), the most tillers will be produced when the soil water holding capacity is 80%. Such as deep-water irrigation, when the water layer is more than 8 cm, the tiller node light is weak, the oxygen is insufficient, and the temperature is low, so that the tiller is inhibited. However, when the field is too dry and the water holding capacity is less than 70%, the tillering will stop.

4. Nutritional requirements. More nutrition is needed in tillering, and more effective tillering is needed. Nutrition can promote tillering and growth faster and more. If there is less nutrition, less tillering or stop. Nitrogen, phosphorus and potassium are the main nutrients needed, especially nitrogen fertilizer. The best nitrogen, phosphorus, potassium combined with topdressing is the most favorable.

Requirements for external conditions at jointing and booting stage

The jointing and booting stage is the period of both vegetative growth and reproductive growth, in which the growth and development of rice increases rapidly, the root group is the largest, the leaf area of rice plant is the largest, and the panicle begins to differentiate at the same time. Jointing and booting is the key period for determining the number of grains per panicle, the consolidation period for the number of effective panicles per mu, and the determining period for grain weight, the main factor is the influence of external conditions.

1. Nutrient requirements. In the process of young panicle differentiation, the root group of water root increases continuously, and the last three leaves grow out one after another, and both vegetative growth and reproductive growth need nutrients. If there is a lack of nutrition in this period, it will have an adverse effect on young panicle differentiation. Therefore, it is necessary to carry out mid-tillage topdressing in production, about 30-40 days before heading, in order to promote spikelet differentiation and increase the number of secondary branches, this fertilizer can also be called "flower-promoting fertilizer"; fertilizer can be sprayed once 10-20 days before heading, that is, male and female core formation stage and pollen mother cell meiosis stage, the most need fertilizer to prevent spikelet abortion and ensure more grains, this period of topdressing is "flower-protecting fertilizer".

2. Temperature requirement. The suitable temperature for young panicle differentiation was 26 ℃ ~ 30 ℃, and 35 ℃ day and night and 25 ℃ night temperature were more favorable for large panicle formation. The external temperature of young panicle differentiation is 15 ℃ ~ 18 ℃, but the most sensitive period is meiosis. In the stage of meiosis, the harm to high and low temperature will cause a large number of abortion and infertility of spikelets.

3. Lighting requirements. The light intensity is closely related to the young panicle differentiation, and the light intensity is beneficial to the young panicle differentiation. According to the experiment, it is proved that the spikelet degeneration is 30% more than that of the control when shaded by two layers of sand cloth during the young panicle differentiation period. If there are more overcast and rainy days, less sunshine and too much closure, the ventilation is not good. Therefore, the light time in Guiyang is less, so the rice density is reasonable to promote a certain amount of photosynthetic crops, and the increase of organic matter can grow rice with large spikes and many grains.

4. Moisture requirement. The period from young panicle differentiation to heading is the period when rice needs the most water in its life, especially in the pollen mother cell meiosis stage, which is the most sensitive, so the field capacity must be maintained at more than 90% during this period, if water shortage will affect floret development. However, if too much water is flooded, it will also cause adverse effects, such as complete flooding will also lead to death.