Mineral Nutrition

(b) Iron is essential for the formation of chlorophyll.

Zinc is needed for synthesis of auxin.

Boron plays a role in pollen grain germination.

Manganese is involved in the splitting of water to liberate $O_2$ during photosynthesis.

Iron $(Fe)$ deficiency is a plant disorder also known as "lime-induced chlorosis".

Zinc deficiency occurs when plant growth is limited because the plant cannot take up sufficient quantities of this essential micronutrient from its growing medium. boron deficiency are expressed at growing tips of the root or shoot, and generally include stunting and distortion of the growing tip that can lead to tip death, brittle foliage, and yellowing of lower leaf tips.

Manganese deficiency causes yellowing of leaves and undergoes interveinal chlorosis.

(d) Anabaena is a nitrogen fixing blue-green alga composed of barrel-shaped cells held in a gelatinous matrix.

So it can fix atmospheric nitrogen.

Anabaena may produce a few different toxins, including anatoxin and microcystin.

Ingestion of small amounts of toxin can cause gastrointestinal distress.

If elevated levels of the algal toxin microcystin are present in the water and ingested, serious liver damage can result.

(b) Rhizobium is a symbiotic nitrogen fixer. Azospirillum is a nitrogen fixing fungus and Nostoc is anaerobic.

(a) Inulin and raphides crystals are reserve materials in plants.

Inulin is a polysaccharide (a polymer of fructose) and is present in compositae.

Raphides are bunches of needle like crystal of calcium oxalate found in certain plant cells.

(a) Azolla performs nitrogen fixation through its colonies of Anabaena azollae, which have the capacity to fix atmospheric nitrogen.

(a) A molecule of $N_2$ is changed to ammonia by nitrogenase.

Transaminase transfers amino group from one substrate to another.

(a) Molybdenum is a component of nitrogenase and nitrate reductase involved during $N_2$ fixation.

Copper is essential for photosynthesis and respiration.

Zinc is involved in synthesis of auxin.

Manganese is an activator of enzymes involved in nitrogen metabolism.

(b) Leghaemoglobin scavenges oxygen to protect nitrogenase from O2 inactivation.

(a) Nitrifying bacteria oxidize ammonia → nitrite (Nitrosomonas) then nitrite → nitrate (Nitrobacter).

(b) Anabaena (cyanobacteria) — prokaryotic autotrophic nitrogen fixer — lives in Cycas root coralloid roots.