91Ó°ÊÓ

Assertion: Leguminous plants are nitrogen fixers. Reason: Leguminous plants have rhizobium in their root nodules.

Assertion: The use of fertilizers greatly enhances the crop productivity. Reason: Irrigation is very important in increasing crop productivity.

Assertion: Hydroponics is uscd for solution culture. Reason: A balanced nutricnt solution contains both cssential and non-cssential clements.

Assertion: Nitrogen is very cssential for sustenance of lifc. Reason: Plants cannot use atmospheric nitrogen directly.

Assertion: The movement of ion is usually called flux. Reason: The concentration of essential elements below which the plant growth is retarded is termed as critical concentration.

Assertion: Iron takes part in the electron transport system of mitochondria. Reason: Iron has no role in chlorophyll synthesis.

Assertion: Rhizobium fixes nitrogen in the symbiotic association with root nodules of leguminous plants only. Reason: Biological nitrogen fixation is anaerobic process.

Assertion: Nitrogen fixing bacteria in legume root nodules survive in oxygen depleted cells of nodules. Reason: Leghaemoglobin completely removes oxygen from the nodule cells.

Assertion: Deficiency of sulphur causes chlorosis in plants. Reason: Sulphur is a constituent of chlorophyll, proteins and nucleic acids.

Assertion: \(\mathrm{S}\) and \(\mathrm{Ca}\) are immobile. Reason: \(\mathrm{S}\) and \(\mathrm{Ca}\) are part of the structural component of cell and hence it is not easily released.