Nitrogen Fixation in Leguminous Plants - Class VII

Leghaemoglobin is an oxygen-binding protein found in the root nodules of leguminous plants. It gives the nodules their characteristic pink or red color.

Leghaemoglobin is an iron-containing protein (a hemoprotein), not a Molybdenum-Iron (Mo-Fe) protein. Nitrogenase is the Mo-Fe protein involved in nitrogen fixation.

Statements I and ii are correct. Rhizobium leguminosarum is also known as Bacillus radicicola. Nitrifying bacteria (Nitrosomonas, etc) are chemoautotrophs. They use inorganic energy sources. However, the enzyme nitrogenase is highly sensitive to oxygen and gets readily oxidised in it's presence and Leghaemoglobin creates anerobic conditions for the enzyme nitrogenase by scavenging the oxygen molecules.

Nitrogenase is highly sensitive to oxygen. Leghaemoglobin acts as an oxygen scavenger, maintaining the low-oxygen (anaerobic) environment necessary for the nitrogenase enzyme to function.

Nitrogenase is the essential enzyme for biological nitrogen fixation. If it is inactivated, the plant cannot convert atmospheric nitrogen into ammonia.

Leghemoglobin supports the centralization of free oxygen in the cytoplasm of contaminated plant cells to guarantee the best possible capacity of root knobs. Its capacity is to help give oxygen to the breathing harmonious bacterial cells in root nodules of leguminous plants in a way practically equivalent to hemoglobin transporting oxygen to breathing tissues in creatures.

Soya bean is a legume. Leguminous plants contain root nodules. Nitrogen fixing bacteria rhizobium is present in the root nodules of leguminous plants which fix the nitrogen naturally. So, it does not require an outer supplement for nitrogen or nitrogen fertilizer.

Leghaemoglobin is a hemoprotein found in the root nodules of leguminous plants.  In plants colonized by Rhizobium, such as alfalfa or soybeans, the presence of oxygen in the root nodules would reduce the activity of the oxygen-sensitive nitrogenase, an enzyme responsible for the fixation of atmospheric nitrogen.   

Diazotrophy is the process of biological nitrogen fixation, where atmospheric nitrogen is converted into ammonia. Leghaemoglobin is crucial for this process in legumes.

• Leghaemoglobin (also leghemoglobin or legoglobin) is an oxygen carrier and hemoprotein found in the nitrogen-fixing root nodules of leguminous plants. 
• Leghaemoglobin buffers the concentration of free oxygen in the cytoplasm of infected plant cells to ensure the proper function of root nodules.

So, the correct answer is "transports oxygen to the root nodule".

Microorganisms which, when applied to seed, plant surfaces, or soil, colonizes the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Rhizobium can be used as biofertilizer. Rhizobium are found in the soil and after infection, produce nodules in the legume where they fix nitrogen gas (N2) from the atmosphere turning it into a more readily usable form of nitrogen.

Leg-haemoglobin is an oxygen carrier. It is found in root nodules of leguminous plants. It is red in colour and is a hemoprotein. It provides or helps in providing oxygen to symbiotic bacterial cells. 

Leghaemoglobin helps to mantain internal oxygen in symbiotic nodules, because this protein has ten times more affinity for oxygen as compared to blood pigment haemoglobin.Therefore they acts as oxygen scavenger.

Rhizobium is microaerophilic rod shaped gram negative bacteria found in association with legume plants in root nodules. These bacteria fix atmospheric nitrogen into ammonium ions, which can be readily assimilated by plants.

Plants cannot consume atmospheric nitrogen directly, because in atmosphere nitrogen occurs in stable diatomic form. The atmospheric nitrogen needs to be converted into plant usable forms like nitrate, nitrite and ammonium ion. This process is called as nitrogen fixation. 

Nodules develop in the roots of leguminuos plants like pulses and grams. These nodules have a very specific function. They inhabit rhizobium bacteria. it is a type of nitrogen fixing bacteria, It absorbs free nitrogen from the atmosphere and converts it into nitrites and nitrates and fixes it in the soil. From soil, plants absorb nitrogen fixed by the bacteria. So, nitrogen requirement of leuminuous plants is fulfilled.

The primary function of leghaemoglobin is to bind oxygen, thereby protecting the oxygen-sensitive nitrogenase enzyme from inactivation.

In the roots of legumes, there live many bacteria, who through their own metabolic processes are able to convert the nitrogen gas into ammonia or ammonium, depending on the acidity of the soil. Converting nitrogen gas into a more usable form is extremely difficult and is the reason that this process is so specialized. While ammonium may be usable by a few plants, the majority cannot use it and another process is required. Nitrifying bacteria oxidize the ammonia creating nitrite then nitrate allowing for the nitrogen to be assimilated into the plants.

Many rhizobia, nitrogen fixing bacteria, live in a symbiotic relationship with plants known as legumes. In such plants, the presence of oxygen in the root nodules would reduce the activity of the oxygen-sensitive nitrogenase. In these situations, the roots of such plants produce a protein known as leghemoglobin. Leghemoglobin buffers the concentration of free oxygen in the cytoplasm of infected plant cells to ensure the proper function of root nodules. Leghemoglobin is a nitrogen or oxygen carrier; naturally occurring oxygen and nitrogen interact similarly with this protein. Hence option B is correct.

Leghaemoglobin is an oxygen scavanger. It combines with oxygen and protects nitrogenase, which catalyses the fixation of nitrogen under anaerobic conditions.

Leguminous plants are in symbiotic association with nitrogen-fixing bacteria like Rhizobium. These bacteria invade root hairs of leguminous plants and forms root nodules in which they fix nitrogen. A red pigment present in the root nodules of leguminous plants is known as leghaemoglobin. Leghaemoglobin is an oxygen-carrier molecule.  It protects nitrogen-fixing enzyme nitrogenase from the side effect of oxygen as the enzyme is highly sensitive to oxygen.

Legumes are in symbiotic association with nitrogen-fixing bacteria like Rhizobium. They fix nitrogen with the help of bacteria that live in their roots. These bacteria invade root hairs of leguminous plants and forms root nodules in which they fix nitrogen. Rood nodules are found in some other plants also apart from leguminous plants. A red pigment present in the root nodules of leguminous plants is known as leghaemoglobin. 

Atmospheric nitrogen is not available to the plants. Nitrogen fixing bacteria converts atmospheric nitrogen into ammonium compounds and make it available to the plants. There are two types of bacteria, free-living and symbiotic. Example of free living nitrogen fixing bacteria include Azotobacter. The example of symbiotic nitrogen fixing bacteria includes Rhizobium. Rhizobium lives in symbiotic association with the legume plants in the root nodules and fixes atmospheric nitrogen. Root nodules of legume plants contains leghaemoglobin. This acts as an oxygen scavanger. 

Leguminous plants are in symbiotic association with nitrogen-fixing bacteria like Rhizobium. These bacteria invade root hairs of leguminous plants and forms root nodules in which they fix nitrogen. A red pigment present in the root nodules of leguminous plants is known as leghaemoglobin. Leghaemoglobin is an oxygen-carrier molecule.  It protects nitrogen-fixing enzyme nitrogenase from the side effect of oxygen as the enzyme is highly sensitive to oxygen.

The root nodules of the leguminous plants contain an oxygen-binding heme protein called leghemoglobin. It is present in the cytoplasm of infected nodule cells at high concentrations. The function of  leghemoglobin is to help transport oxygen to the respiring symbiotic bacterial cells in a manner analogous to hemoglobin transporting oxygen to respiring tissues in animals. It has a high affinity for oxygen (approximately, ten times higher than the ß chain of human hemoglobin). Thus, it acts as a oxygen scavenger.
Hence, the correct answer is option (A).

Lectins are sugar-binding proteins that play a key role in the recognition and attachment of compatible Rhizobium bacteria to the root hairs of host leguminous plants.

The root nodules contain pink colored pigment contains a protein called leg-hemoglobin.

Leghaemoglobin is an oxygen carrier found in the nitrogen fixing root nodules of leguminous plants. Rhizobium is a free living bacteria that can fix atmospheric nitrogen.

Leghaemoglobin present in plant nodules ,impart a characteristic pink colour to the roots.

Plants are not capable of fixing nitrogen on their own, but need it in one or the other form to make proteins and amino acids. Legumes form root nodules, when they exist in a symbiotic relationship with 'Rhizobia' and therefore, have high levels of nitrogen available to them. These soil bacteria (e.g., Rhizobium, Mesorhizobium, Sinorhizobium) fix the atmospheric nitrogen or dinitrogen, into inorganic compounds, like ammonium, which is then converted into amino acids, which the plants can utilize.

The nitrogenase enzyme is extremely sensitive to oxygen and is inactivated by it. Therefore, the statement that it is 'insensitive to oxygen' is incorrect.

Rhizobium, is a rod shaped, aerobic, nitrogen fixing bacterium present in the root nodules of leguminous plants. It performs symbiotic nitrogen fixation in the root nodules of leguminous plants, in presence of an enzyme dinitrogenase.

So,
the correct option is ‘bacteria are aerobic and nitrogenase are active’.

Under ordinary conditions, the water potential of a root hair cell is negative, typically ranging between -1 and -4 atm, which allows it to absorb water from the soil.

Larger surface area and thinner walls of root hair are required to absorb water efficiently. 

The cells of the roots contain cell sap (solution) at a higher concentration than that of surrounding soil water. As a result, the water is absorbed by the root hairs. This is because the water always travels from a region of high water potential to the region of lower water potential. Here, the soil possesses a higher water potential as compared to the root hair.

Mineral absorption is an active process that requires energy (ATP) and occurs independently of water absorption, which is primarily a passive process driven by water potential gradients.

Transpiratioal or gravitational pull exert strain so they are factors that can cause rupture of the column. 

Water enters root hairs from the soil primarily due to osmosis, which is driven by the difference in Osmotic Pressure (O.P.) between the root cell sap and the soil water. Root hairs have a higher solute concentration, resulting in a higher osmotic pressure that pulls water inward.

Water flows from a region of higher water potential (or lower diffusion pressure deficit / lower osmotic pressure relative to turgor) to a region of lower water potential. Alternatively, using DPD = OP - TP, for cell A: DPD = 10 - 4 = 6. For cell B: OP=4, TP=4, DPD = 0. Since water moves from lower DPD to higher DPD, water flows from cell B (DPD 0) to cell A (DPD 6).

Phosphorus, sulphur, nitrogen and potassium most readily mobilise while calcium is structural component which is not remobilised.