Although about 80% of the nitrogen in the air can not be directly used by ordinary plants, peanuts,but soybeans, alfalfa and other leguminous plants can only convert the molecular nitrogen in the air into ammonia nitrogen that can be used by plants through symbiotic nitrogen fixation with rhizobia.
After the seeds germinate and take root, rhizobia invade the roots from the root hairs.Under certain conditions, they form nodules with nitrogen fixing ability.
Under the action of nitrogen fixing enzymes, the bacteroids in the nodules convert molecular nitrogen into ammonia nitrogen.At the same time, each nodule is a miniature nitrogen fertilizer plant, which continuously delivers nitrogen to plants for utilization.
The number of indigenous rhizobia around leguminous crops is small, which is difficult to meet the needs of crop growth.Leguminous crops in the world need to be inoculated with rhizobial agents manually.The nitrogen fertilizer produced by rhizobial agents to crops will not cause environmental pollution,do not need long-distance transportation, and there is no nitrogen loss during use.
However, the loss rate of chemical nitrogen fertilizer applied manually is often more than 50%.When leguminous crops germinate and grow root hairs, rhizobia are stimulated and attracted by lectins secreted by root hairs,and accumulate in the rhizosphere and root surface in large quantities. After the root hair contacts with the rhizobia,first the cell wall becomes soft, and then the root hair curls, and then the cell wall collapses.
The rhizobia then invades the root hair until the cortex of the root.The rhizobia propagates in large numbers in the cortex and turns into bacteroids.At this time, the cortex of the root proliferates in large numbers, forming nodular tissue, and finally protruding from the root to form root nodules.When the section of the effective root nodules is pink, it indicates that the root nodules have entered the mature stage and begin to fix nitrogen,
And provide nitrogen to the plant.
Artificial inoculation of rhizobia with excellent nodulation and nitrogen fixation performance can improve the symbiotic nitrogen fixation efficiency.