1. 1. The vegetative growth period is the growth of rice vegetative body, which is divided into seedling stage and tillering stage. Production is divided into seedling stage and big (original) field stage (from transplanting to greening to jointing).
1.2, the reproductive growth period is the growth of fruiting organs, from young panicle differentiation to flowering and fruiting, and it is divided into long panicle period and flowering and fruiting period. The differentiation from young panicle to heading is the same period of vegetative growth and reproductive growth, and the reproductive growth period is basically after heading. The long panicle stage starts from young panicle differentiation to heading stage, generally about 30 days. The fruiting period from heading to flowering to grain maturity varies with climate and varieties. Between 50 days.
1.3. The growth type of rice (the relationship between young panicle differentiation and jointing) is different in early, middle and late rice varieties, and the early rice varieties are called overlapping growth type after young panicle differentiation; Mid-season rice varieties, jointing and young panicle differentiation at the same time, are called continuous type; Late rice varieties differentiate young panicles at intervals after jointing stage, which is called separated growth type.
2. Stability and variability of rice varieties in growth period. The growth period of rice varieties is controlled by their own genetic characteristics and influenced by environmental conditions.
2. 1. Stability of growth period of rice varieties The same variety is cultivated in the same area, the same season and different years, and its growth period is relatively stable due to similar ecological conditions between years. Early-maturing varieties always show early maturity, and late-maturing varieties always show late maturity. This stability is mainly controlled by genetic factors. Therefore, in production practice, it can be divided into early rice, whole growth period >; 125th day, medium rice >; 150 days, continuous cropping of late rice > 140 days, late rice in one season > 170 days, and the difference of growth period of early, middle and late rice can also be divided into early, middle and late rice varieties to meet the needs of natural conditions and farming systems in different regions, thus ensuring the relative stability and continuity of agricultural production in a certain period.
2.2. The variability of rice varieties in growth period varies with different ecological environment and cultivation conditions. When the same variety is cultivated in different areas, the growth period is prolonged with the increase of latitude and altitude, and conversely, it is shortened with the decrease of latitude and altitude. The cultivation of the same variety in different seasons shows that the growth period is shortened with the delay of sowing date and extended with the advance of sowing date. Early rice varieties are cultivated as continuous cropping late rice, and the growth period is shortened; Introduced from the south to the north, the growth period is prolonged.
3. The "three characteristics" of rice varieties are the genetic characteristics of light sensitivity, temperature sensitivity and basic nutritional growth. In different regions and different cultivation seasons, the growth period of rice varieties (from sowing to heading) is basically determined by the comprehensive effect of the "three characteristics" of the varieties. Therefore, the three characteristics of rice varieties are the essence that determines the length and change of rice varieties. The three characteristics of rice are formed under the influence of climatic conditions and cultivation seasons. For any specific variety, these three characteristics are an interrelated whole.
3. 1. The photosensitivity of rice varieties is characterized by the change of growth period due to the length of sunshine in the temperature range suitable for rice growth, which is called the photosensitivity of rice. For photosensitive varieties, short sunshine can accelerate their development and change and lead to early heading differentiation, that is, heading earlier than a certain day; When it is longer than a certain day, the heading is obviously delayed, also known as "the temporary day length of delayed heading", which is the upper limit of the day length to induce the differentiation of young panicles. Different rice varieties and different planting areas have different temporary days to postpone heading. In the northern and southern rice areas of China, the growth period of rice is mostly between >: 65438 and 06 hours.
3.2. The temperature sensitivity of rice varieties is within the temperature range suitable for rice growth. High temperature will shorten the growth period of rice, while low temperature will prolong the growth period. This characteristic that the growth period changes due to high and low temperatures is called the temperature sensitivity of rice varieties. The growth period of rice varieties will be shortened at high temperature, but the degree of shortening varies with the characteristics of rice varieties. The temperature sensitivity of late rice varieties is stronger than that of early rice, but the development and transformation of late rice varieties are mainly controlled by the conditions of day length. When the day can't meet the requirements, the effect of high temperature can't be shown. Mid-season rice varieties are between early rice and late rice.
3.3. Basic vegetative growth of rice varieties The vegetative growth period of rice that cannot be shortened under the influence of high temperature and short sunshine before it enters reproductive growth is called the basic vegetative growth period of rice. Not affected by environmental factors, also known as the basic nutritional growth of varieties. The part where the vegetative growth period is shortened by short-day high temperature is called digestible vegetative growth period.
The "three characteristics" of rice are formed under the influence of climatic conditions and cultivation seasons. For any variety, these three attributes are an interrelated whole. According to the light and temperature sensitivity of varieties and the length of basic vegetative growth period, the types of light and temperature response were divided. In fact, it is to combine the three characteristics of different ecological types of rice seeds. Most early rice varieties have weak photosensitivity, short to medium basic vegetative growth period, medium sensitivity to temperature, no strong photosensitivity and long basic vegetative growth period; Most mid-season rice varieties have long basic vegetative growth period, medium strong temperature sensitivity and weak light sensitivity; Late rice varieties have strong photosensitivity, short to medium basic vegetative growth period and strong to medium temperature sensitivity. The basic vegetative growth period of late rice in China is short, and there is no weak or moderate photosensitivity. The temperature sensitivity of late rice can only be reflected in short sunshine. Early rice varieties planted in temperate high latitudes can heading normally under the condition of long sunshine in summer and mature before the arrival of low temperature, while in the middle and lower reaches of the Yangtze River, under the condition of long sunshine, young panicles begin to differentiate and complete development and transformation. The late rice type is swollen, which is not suitable for planting in temperate high latitudes, but it can be planted as single-season late rice and double-season late rice in the middle and lower reaches of the Yangtze River. Among the mid-season rice varieties, the early-maturing mid-season rice is biased towards early rice, while the late-maturing mid-season rice is biased towards late rice. When cultivated in early season, the heading date was obviously delayed compared with early rice, and when cultivated in late season, it was delayed compared with late rice.
4. The application of "three characteristics" of rice in production.
4. 1. Introduction and application: Generally, it is not appropriate to introduce early-maturing varieties from different latitudes and from north to south, because they are sensitive to high temperature and prone to early panicles, spikelets and few grains, thus reducing production; It is easy to introduce early rice varieties with weak photosensitivity from the south to the north, but it is difficult to introduce late rice varieties with strong photosensitivity. Introduction at different altitudes, at the same latitude, from high altitude to low altitude, shortens the growth period and matures early, which is more suitable for introducing late-maturing varieties. On the contrary, the introduction from low altitude to high altitude should be based on early and middle mature clocks.
4.2. Application in cultivation In order to meet the requirements of various farming systems, rice variety collocation and sowing date arrangement, and ensure stable and high yield, it is necessary to consider the light and temperature characteristics of varieties. Varieties should be matched with three-season rice fields in the south, and late-maturing early rice varieties with weak photosensitivity, moderate temperature sensitivity and long basic nutritional growth period should be selected for early rice; However, early-maturing varieties have strong temperature sensitivity, short basic vegetative growth period, slightly larger seedling ridge, easy heading early and difficult to improve yield. Due to the strict requirements for short-day conditions, late-maturing rice varieties can't mature in early season, so they can only be cultivated as late rice.
Varieties with strong temperature sensitivity should arrange sowing date in advance and cultivate strong seedlings in order to make full use of the early low temperature for vegetative growth. If this variety is sown late, even if the seedling ridge is very short, it will often lead to early ear; For late rice varieties with strong photosensitivity, Yangling has great flexibility. In the cultivation of continuous cropping late rice, sowing should be delayed appropriately, but heading should be controlled at the local safe heading stage.
5. Rice variety classification is the basic unit of cultivated rice formed by long-term artificial and natural selection under certain areas and cultivation conditions. It has certain genetic characteristics, and individuals in the same variety have consistent botanical and biological characteristics, and have strong adaptability to local natural conditions and farming systems.
5. 1. Varieties can be divided into early rice (early, middle and late maturity), middle rice (early, middle and late maturity) and late rice (early, middle and late maturity). Maturity is related to place and time. The division of national maturity of rice varieties in China is based on the heading date of various varieties in Nanjing. The division of regional maturity depends on the length of local growth period of regional varieties. Varieties with different maturity types have different growth days and types, and grow under different ecological conditions, so corresponding cultivation measures should be taken according to the characteristics of maturity.
5.2. According to the characteristics of panicles and grains, it can be divided into large panicle type and multi-panicle type, with large panicles, thick stems, large leaves, few tillers, few panicles per plant and large panicles and many grains; Multi-spike type, thin stems, small leaves, more tillers, more spikes per plant and less grains per spike. In the big spike cultivation, the measures of low population and strong individuals, paying attention to fertilization in the middle stage and leaving roots and leaves in the later stage are adopted; Multi-spike varieties are suitable for close planting, nitrogen adjustment in the middle stage and lodging prevention in the later stage.
5.3. According to the classification of plant height, it is divided into high, medium and short varieties. The stalk rice is short and the indica rice is high. Its standard: the plant height below 100 cm is short, the plant height above 120 cm is high, and the middle is medium.
5.4. According to the classification of hybrid rice and conventional rice, it shows obvious heterosis and is easy to obtain large-area high yield, but the sterile rate of seed production is high and the cost is high; Conventional rice does not produce seeds, which is conducive to accelerated propagation of improved varieties and lower cost. At present, the rice production in China is the coexistence of hybrid rice and conventional rice, mainly conventional rice.