Table Comparing Leguminous and Non-Leguminous Plants
Leguminous and non-leguminous plants are reported to belong to the flowering plant family in the plant kingdom. Leguminous plants have the property of fixing atmospheric nitrogen due to the presence of Rhizobium sp. in their roots, unlike non-leguminous plants. The nitrogenase complex present in these diazotrophs helps in the conversion of nitrogen to ammonia. However, some non-leguminous plants have been reported to fix atmospheric nitrogen. Examples include those which form symbiotic associations with Frankia sp. and Azolla sp, like alder trees and shrubs (Alnus sp.), pea plants and sweet-fern (Comptonia peregrina). Nitrogen is a limiting factor in plant growth and development. Plants are reported to absorb the nitrogen available in the soil by their roots in the form of ammonia. The ammonia is made available to the plants by the nitrogen-fixing bacteria with the aid of the nitrogenase complex.
Difference Between Leguminous and Non-leguminous Plants
Leguminous Plants
Leguminous plants are the group of angiosperms that enrich the soil with nitrogen-rich compounds by the process of biological nitrogen fixation.
Certain prokaryotes have the capability to fix atmospheric nitrogen through a process known as biological nitrogen fixation (BNF) and convert the atmospheric N2 to NH3, which is absorbable by plants. The bacteria are called diazotrophs, and they are reported to have nitrogenase, the enzyme complex that catalyses the whole process. Beans and peanuts are leguminous plant examples that can fix nitrogen. These plants are agriculturally beneficial because they enrich the soil with important nutrients that are essential for the growth of the crops. Leguminous plants can also improve the quality of the soil and can prevent soil erosion. Leguminous crops always produce pods as their fruit. The seeds of the plants are enclosed in these pods. The leguminous plants have tap roots that penetrate deep into the soil. The leguminous plants having symbiotic relations with the diazotrophs receive an ample amount of nitrogen, reducing the requirement for chemical fertilisers.
Leguminous Plants Examples
Leguminous plants serve as the staple food in our diet. Beans, cowpeas, chickpeas, kidney beans, alfalfa and groundnuts are the most common legumes. The leaves of the plant are stipulated and compounded. The fruits are the pods.
Non-Leguminous Plants
Non-Leguminous plants belong to different classes, except Fabaceae. These plants do not bear pods, and they do not have Rhizobium sp. associated with the roots. These plants do not have the capacity to replenish the soil with nitrogen. Instead, they deplete the soil nitrogen.
Non-Leguminous Plants Examples
Examples of non-leguminous plants include Tal or Asian palm B.flabellifer Sorisha or black mustard B.nigra. Other non-leguminous plant examples include Rose, mango, ficus, etc.
Nitrogen Fixation in Non - Leguminous Plants
The process of biological nitrogen fixation involves the fixation of atmospheric nitrogen to ammonia with the help of the nitrogenase complex present in diazotrophs or the nitrogen-fixing bacteria. These bacteria pass the fixed atmospheric nitrogen into a plant host. Leguminous plants have Rhizobium sp. association in their roots that aid in this process. The non-leguminous plants are the exception, and they do not have Rhizobium sp. in their roots. Examples of nitrogen fixation in non-leguminous plants include an association between sugarcane and endophytic bacteria Gluconacetobacter diazotrophicus. Association of tropical grasses such as Digitaria sp. and Paspalum sp. with Azospirillum sp, and an association of coffee and maize with Burkholderia sp.
Parasponia sp. is the only exception; it belongs to a non-legume lineage to a rhizobial symbiosis system that is less advanced than the leguminous plants. In the non-leguminous plant Gunnera, the nitrogen-fixing bacteria Cyanobacterium sp. and Nostoc sp. are reported to enter the mucilage-secreting glands located in the stem and axis of the leaves. These form membrane-bound vesicles in the cytoplasm that is similar to rhizobium–legume symbiosis, but in this case, nodule formation does not occur.
Process of Nitrogen Fixation by Nitrogen-fixing Bacteria
List of Leguminous Plants
Leguminous plants help in the enhancement of nitrogen-rich compounds in soil that is required for the growth and development of plants by the process of biological nitrogen fixation. The list of leguminous plants is given below.
Interesting Facts
The leguminous plants are popular for their nitrogen-fixing capacity; however, some non-leguminous plants are also reported to fix atmospheric nitrogen by maintaining symbiotic relation with Frankia sp.
Key Features of Leguminous and Non-Leguminous Plants
Legumes can be annual, biennial, or perennial; these plants are reported to bear pods or seeds.
Leguminous plants are important in agriculture. They help in the enrichment of soil quality by enhancing the number of natural fertilisers (ammonium) in soil by the bacteria found in the roots.
The leaves of leguminous plants are pinnate, compound and stipulated. Whereas; leaves of non-leguminous plants can be simple or compound; stipulated or unstipulated.
Leguminous plants form symbiotic relations with Rhizobia sp. On the other hand, non-leguminous plants form symbiotic relations with actinomycetes.
Leguminous plants are used as a staple food in the human diet; they can be used in crop rotation as these plants can fix atmospheric nitrogen. On the other hand, non-leguminous plants can be used for animal grazing and can also be used in the human diet.
FAQs on Leguminous vs Non-Leguminous Plants: Differences Explained
1. What is the fundamental difference between leguminous and non-leguminous plants?
The fundamental difference lies in their ability to perform biological nitrogen fixation. Leguminous plants form a symbiotic relationship with nitrogen-fixing bacteria (like Rhizobium) in special structures on their roots called root nodules. This allows them to convert atmospheric nitrogen into a usable form. Non-leguminous plants lack this specific symbiotic relationship and cannot form these types of root nodules, so they must absorb nitrogen from the soil.
2. Can you provide common examples of both leguminous and non-leguminous plants?
Yes, here are some common examples:
- Leguminous Plants: This group, belonging to the family Fabaceae, includes most peas, beans, lentils, chickpeas, peanuts, soybeans, and alfalfa.
- Non-leguminous Plants: This is a vast category that includes most other plants. Common examples are major cereal crops like rice, wheat, and corn (maize), as well as vegetables like tomatoes and potatoes, and fruits like mangoes and apples.
3. Why is the distinction between leguminous and non-leguminous plants so important in agriculture?
This distinction is crucial for a farming practice called crop rotation. Farmers often plant leguminous crops in a field to naturally enrich the soil with nitrogen compounds. After harvesting the legumes, they plant a non-leguminous crop, like wheat or maize, which can then use the abundant nitrogen left in the soil. This sustainable practice reduces the need for expensive and environmentally impactful nitrogen fertilisers, improving soil fertility and crop yields.
4. How exactly does the symbiotic nitrogen fixation in leguminous plants work?
The process is a complex biochemical interaction. The plant roots release chemical signals (flavonoids) that attract Rhizobium bacteria. The bacteria, in turn, release signals that cause the root hairs to curl and form an infection thread, allowing the bacteria to enter the root's cortex. This triggers rapid cell division, forming a root nodule. Inside the nodule, the bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃) using an enzyme called nitrogenase. The plant protects this oxygen-sensitive enzyme with a pinkish pigment called leghaemoglobin and, in return, receives the fixed nitrogen.
5. Do non-leguminous plants have any way to fix nitrogen?
While non-leguminous plants cannot form the classic symbiotic relationship with Rhizobium, nitrogen fixation in their vicinity is still possible. Some non-legumes, like Alnus, form a symbiotic relationship with other nitrogen-fixing bacteria such as Frankia. Additionally, all plants benefit from free-living (non-symbiotic) nitrogen-fixing bacteria like Azotobacter and Clostridium that live in the soil and independently convert nitrogen gas into usable compounds.
6. Besides root nodules, what other botanical features can help identify a leguminous plant?
Beyond the presence of root nodules, plants in the legume family (Fabaceae) often share other distinct characteristics. The most telling feature is their fruit, which is typically a pod or legume that splits open along two seams (like a pea pod). Many also have compound leaves, where a single leaf is made up of multiple smaller leaflets. Their flower structure is also often unique and recognisable.
7. Why did only leguminous plants evolve this specific symbiotic relationship with Rhizobium?
This ability is the result of a highly specialised and ancient evolutionary pathway. It requires a complex genetic and biochemical 'dialogue' between the plant and the bacteria. The plant must produce specific chemical signals to attract the right bacteria, and its genetic code must allow for the formation of nodules. Most other plant families have not evolved this intricate set of genes and signalling pathways, making this symbiotic relationship a unique advantage for the Fabaceae family, allowing them to thrive in nitrogen-poor soils where other plants might struggle.
