The growth and function of Rice Root

The seeds sprout and take root immediately after accelerating germination. At first, only one root, called seed root (main root), grew from the radicle of the seed. The fibrous root that grows from the root point of the stem node is called adventitious root. There are about 5 hairy roots in coleoptile nodes and incomplete leaf nodes, 10 hairy roots in the first, second and third leaves, and about 10-20 hairy roots in the nodes above the fourth leaf. This is because the leaves increase sequentially from the bottom up, the supply of nutrients to the hairy roots increases sequentially, and the hairy roots also increase. Aboveground nodes, generally not rooting. Nutrients made by leaves are transported to the root primordium through vascular bundles of leaf sheaths and stem nodes to promote root formation. The increase or decrease of vascular bundle number is affected by environment and cultivation conditions. Under the condition of moist soil, there is plenty of oxygen, more hair roots and root hairs. Under the condition of deep irrigation, the soil is in a state of reduction, lack of oxygen, affecting root respiration, no root hair and black root and rotten root, 32 ℃ is the most suitable temperature for root growth, when the soil is 25 ℃, the hairy root is more, but shorter, and at 5 ℃, there are few roots. Rice fields irrigated with cold water at the bottom of the reservoir or cold bottom fields also have little rooting. When the depth of transplanting rice seedlings reaches 3 to 4 inches, thin and long elongated internodes will appear, forming two stages of rooting. Plants with two stages of rooting often have few or no tillers, or late tillers become ineffective tillers. And the stem is thin and weak and easy to lodge. Therefore, transplanting rice seedlings should not be too deep.

The root of the bud sheath node can make the bud take root, turn the grain bud and give out the needle. The roots born at the incomplete leaf node and the first complete leaf node play a role in absorbing nutrients during the weaning period of the seedling. The roots produced by the nodes above the second leaf position play a role in the growth of seedlings and the growth after transplantation. Under normal circumstances, rooting is exuberant 7 days after transplanting. The root angle of the initial growth is smaller, the root angle of the middle node is larger, and the root of the upper node is horizontally distributed, like a network. In the later stage, it depends on these roots to absorb water and fertilizer. Therefore, it is not suitable to trample in the field at booting stage, so as not to break the horizontal root which plays a major role in flowering and fruiting.

The root growth is compatible with the aboveground part. The root plays the role of fixation and support, and can synthesize amino acids and other organic substances, which can be transported to the aboveground parts for protein synthesis. 75% of the inorganic nutrients absorbed by the root are needed by the stem and leaf, and only a small part is left in the root. The organic matter needed by the root is supplied from the aboveground part. In this way, the division of nutritional function between roots and stems and leaves is formed, and they promote each other.

The soil environment in which the rice root is located is lack of oxygen, and the oxygen transported from the leaves to the root not only meets the needs of fundamental body respiration, but also secretes some from the epidermis of the root, and the oxygen surrounds the root. to avoid being poisoned by reducing substances in the soil, this phenomenon is called oxygen secretion. The new root secretes more oxygen, is white, has a strong ability to absorb fertilizer and water, and the old root often has scab spots, because the soluble ferrous hydroxide in the paddy field is oxidized into insoluble ferric hydroxide, accumulates around the rhizosphere, and even attaches to the surface of the root. Long-term deep irrigation of rice fields will produce hydrogen sulfide, when the ferric hydroxide around the rhizosphere is not enough to combine with hydrogen sulfide, rice roots will be damaged by toxic substances such as hydrogen sulfide, resulting in rotting roots. When there is black root without rotting root, through drainage open field or drying field, increase the oxygen in the soil, in order to strengthen oxidation, can change the color of black root and avoid rotting root.

For the strength of rice roots, as far as one root is concerned, the tip of the root has the strongest vitality. In the case of a rice plant, the new root is more vigorous than the old one. The root with strong vitality has a strong ability to absorb water and nutrients and has a strong respiration. The strength of respiration is mainly affected by the supply of oxygen and carbohydrates. The heavy clay, which is lack of oxygen, will take away a large amount of oxygen secreted by the rice root, reducing the oxygen needed to supply the root to breathe and reducing the vitality of the root. If too much nitrogen fertilizer is applied, it will cause the leaves to bend and spread fog, so that the lower leaves, which supply nutrients to the rice roots, produce less carbohydrates due to lack of direct sunlight, and the vitality of the roots decreases. Some seedlings grow well in the early stage, but die early in the later stage, and good crops are not good grain. It is mainly due to the lack of oxygen and carbohydrates needed to supply the rice root, the premature senescence of the root, the decline of vitality and the decrease of the ability to absorb water and nutrients; because the leaves do not get enough water and nutrients, they also dry up prematurely, thus affecting the fullness of the grain.