โ `color{Brown}"Nodule formation"` involves a sequence of `color{violet}"multiple interactions"` between `color{violet}"๐๐ฉ๐ช๐ป๐ฐ๐ฃ๐ช๐ถ๐ฎ"` and `color{violet}"roots"` of the host plant.
โ `color{violet}"Principal stages"` in the nodule formation are summarised as follows:
โ `color{violet}"Rhizobia multiply and colonise"` the surroundings of roots and get attached to `color{violet}"epidermal"` and `color{violet}"root hair cells"`.
โ The `color{violet}"root-hairs curl"` and the `color{violet}"bacteria invade"` the root-hair.
โ An `color{violet}"infection thread"` is produced carrying the bacteria into the `color{violet}"cortex of the root"`, where they initiate the `color{violet}"nodule formation"` in the cortex of the root.
โ Then the `color{violet}"bacteria are released"` from the thread into the cells which leads to the `color{violet}"differentiation"` of specialised `color{violet}"nitrogen fixing cells"`.
โ The `color{violet}"nodule thus formed,"` establishes a direct `color{violet}"vascular connection"` with the host for exchange of nutrients.
โ These events are depicted in Figure.
โ The nodule contains all the `color{violet}"necessary biochemical components"`, such as the enzyme `color{Brown}"nitrogenase and leghaemoglobin"`.
โ The enzyme `color{violet}"nitrogenase is a Mo-Fe protein"` and catalyses the conversion of `color{violet}"atmospheric nitrogen"` to `color{violet}"ammonia"`,the first stable product of nitrogen fixation.
โ The reaction is as follows: โ
โ The enzyme `color{violet}"nitrogenase is highly sensitive"` to the `color{Brown}"molecular oxygen"`; it requires `color{violet}"anaerobic conditions"`.
โ The nodules have adaptations that ensure that the `color{violet}"enzyme is protected"` from oxygen.
โ To protect these enzymes, the nodule contains an `color{violet}"oxygen scavenger"` called `color{Brown}"leg-haemoglobin"`.
โ It is interesting to note that these `color{violet}"microbes live as aerobes"` under free-living conditions (where nitrogenase is not operational), but during nitrogen-fixing events, they become `color{violet}"anaerobic"` (thus protecting the nitrogenase enzyme).
โ You must have noticed in the above reaction that the `color{violet}"ammonia synthesis by nitrogenease"` requires a very `color{violet}"high input of energy"` (`color{Brown}"8 ATP"` for each `NH_3` produced).
โ The `color{violet}"energy required"`, thus, is obtained from the `color{violet}"respiration"` of the host cells.
โ `color{Brown}"Nodule formation"` involves a sequence of `color{violet}"multiple interactions"` between `color{violet}"๐๐ฉ๐ช๐ป๐ฐ๐ฃ๐ช๐ถ๐ฎ"` and `color{violet}"roots"` of the host plant.
โ `color{violet}"Principal stages"` in the nodule formation are summarised as follows:
โ `color{violet}"Rhizobia multiply and colonise"` the surroundings of roots and get attached to `color{violet}"epidermal"` and `color{violet}"root hair cells"`.
โ The `color{violet}"root-hairs curl"` and the `color{violet}"bacteria invade"` the root-hair.
โ An `color{violet}"infection thread"` is produced carrying the bacteria into the `color{violet}"cortex of the root"`, where they initiate the `color{violet}"nodule formation"` in the cortex of the root.
โ Then the `color{violet}"bacteria are released"` from the thread into the cells which leads to the `color{violet}"differentiation"` of specialised `color{violet}"nitrogen fixing cells"`.
โ The `color{violet}"nodule thus formed,"` establishes a direct `color{violet}"vascular connection"` with the host for exchange of nutrients.
โ These events are depicted in Figure.
โ The nodule contains all the `color{violet}"necessary biochemical components"`, such as the enzyme `color{Brown}"nitrogenase and leghaemoglobin"`.
โ The enzyme `color{violet}"nitrogenase is a Mo-Fe protein"` and catalyses the conversion of `color{violet}"atmospheric nitrogen"` to `color{violet}"ammonia"`,the first stable product of nitrogen fixation.
โ The reaction is as follows: โ
โ The enzyme `color{violet}"nitrogenase is highly sensitive"` to the `color{Brown}"molecular oxygen"`; it requires `color{violet}"anaerobic conditions"`.
โ The nodules have adaptations that ensure that the `color{violet}"enzyme is protected"` from oxygen.
โ To protect these enzymes, the nodule contains an `color{violet}"oxygen scavenger"` called `color{Brown}"leg-haemoglobin"`.
โ It is interesting to note that these `color{violet}"microbes live as aerobes"` under free-living conditions (where nitrogenase is not operational), but during nitrogen-fixing events, they become `color{violet}"anaerobic"` (thus protecting the nitrogenase enzyme).
โ You must have noticed in the above reaction that the `color{violet}"ammonia synthesis by nitrogenease"` requires a very `color{violet}"high input of energy"` (`color{Brown}"8 ATP"` for each `NH_3` produced).
โ The `color{violet}"energy required"`, thus, is obtained from the `color{violet}"respiration"` of the host cells.