MCQ
The common Nitrogen-fixer in paddy fields is
- AFrankia
- BRhizobium
- CAzospirillum
- DOscillatoria
Explanation:
Azospirillum is a microaerophilic nitrogen fixer commonly found in association with the roots of cereals and grasses of interest.
It colonizes the root mass and fixes nitrogen in association with plants.
It is the popular nitrogen-fixer used in paddy fields along with Azolla. When a small amount of it is added to the soil, it multiplies into million and is capable of providing up to 20-40kg of nitrogen per hectare per season.
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| Column - $I$ | Column - $II$ |
| $(a)$ Herbivores-Plants | $(i)$ Commensalism |
| $(b)$ Mycorrhiza-Plants | $(ii)$ Mutualism |
| $(c)$ Sheep-Cattle | $(iii)$ Predation |
| $(d)$ Orchid-Tree | $(iv)$ Competition |