Rice originated from low-latitude high-temperature, rainy mountain valleys and swamps. It took a long time to evolve to the mid-high latitudes. The history of the origin and evolution of rice determines the various physiological and ecological characteristics of rice that currently live. Rice germination
(1) Water Research Pan Ruichi pointed out that if the water absorption of indica rice is equivalent to 25% or more of the seed's own weight (air-dried weight), it can germinate, and the water intake of indica rice should reach 35% or more. The water requirement for rice germination is not higher than that for dry cultivation and is still lower (when wheat seeds require 45% water absorption to enter the germination). This is related to the origin of rice in the monsoon marsh area. Both wild rice and ancient rice germinate at the beginning of the monsoon. , The low water absorption requirement is good for the season.
(2) Oxygen rice seeds germinate in two ways: one is anaerobic respiration, and less energy is produced from alcohol and CO2. Before the rice seeds are broken, due to the resistance of the seed coat to oxygen entry, anaerobic respiration is predominant. At this time, it is required to constantly change the water during soaking so as to prevent alcohol taste. The second is to break into the chest and expose to aerobic respiration. The respiratory intensity is 30 times stronger than that before dew-whitening.
(3) The temperature of indica rice seeds is the fastest when they are at 30°C, and the amount of water (25% of the dry weight of the seeds) is as long as 30 hours, 20 hours at 20°C, and 140 hours at 15°C. Compared with japonica rice, japonica rice has lower water absorption than japonica rice at high water temperature, and faster than japonica rice at low water temperature. Regardless of long or long roots, 32C is the optimum temperature for indica seed germination, and japonica rice germinates fastest at 34°C, which is consistent with the masses' experience of “high temperature breaking of the chestâ€.
Rice emergence and seedling growth
(1) Temperature The East China Agricultural Research Institute Meteorological Group (1958) used 4 varieties and 6 different temperature-controlled treatments. The study pointed out that the minimum temperature for emergence was 12°C for indica and 14°C for indica, but maintaining such temperature and emergence It is very slow, and the growth condition is also very poor. The emergence above 15°C is relatively normal, and the emergence above 20°C is smooth.
What is the optimum temperature for the emergence of rice? According to Yan Yurui (1956), in terms of growth rate, japonica rice is the fastest at 32-34°C and japonica rice is the fastest at 30-32°C, but seedlings grow fast and are easy to grow.
The study on the relationship between cell division and temperature at the growth point of rice seedlings indicated that at 20-25°C, tillering was the most vigorous. Therefore, 20-25°C is the most suitable for the requirements of strong seedlings.
(2) After three-leaf stage of light seedlings, the endosperm nutrient is consumed, and it is necessary to rely on the photosynthesis of its own leaves to supply seedlings for growth. Therefore, seedlings need good lighting conditions. According to Mo Huidong (1978), the critical illuminance of the leaf area per plant is 25.6-30.310-5J/m2. Below the critical illuminance, seedling growth will be inhibited.
(3) Moisture and Oxygen Rice originated from wetlands in swamps and has been adapted to flooding conditions since the seedling stage. Rice seedlings have fissured aerenchyma in the body, which is conducive to oxygen as far as the root system. However, before the three-leaf stage, the aerenchyma is not very developed, and it is advisable for Putian to keep moist. After the three-leaf stage, there may be a shallow water layer, and in the dry conditions, it may continue to be moist, or slightly dry, to facilitate the growth of roots, and the seedlings are short and strong. Http://
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