Zoology Test Paper

Sodium is not generally regarded as an essential nutrient for plants. However, sodium can substitute for potassium to a greater or lesser extent in different plant species.

  Nickel is not an essential micronutrient.

 Deficiency of molybdenum causes mottling and necrosis of leaves.

 Boron is necessary for translocation of sugars in plants.

Magnesium ion is present in the center of a chlorophyll molecule. Its deficiency causes the yellowing or whitening of normal green plant tissue which is known as chlorosis. 

Death of the stem and root tips occurs due to deficiency of calcium.

 Root hairs do not play any role in both water and mineral intake.

Plant ash is an indication of mineral salts absorbed by the plant.

 Active mineral absorption depends on expenditure of energy.

Calcium is a macronutrient. It is an essential part of the plant cell wall and helps in the transport and retention of other elements.

Zinc can be absorbed by foliage. Zinc deficiencies can affect plant by stunting its growth, decreasing number of tillers, chlorosis and smaller leaves, increasing crop maturity period, spikelet sterility and inferior quality of harvested products.

In leguminous plants, leghaemoglobin regulates the supply of oxygen to nodule tissue. Therefore, it is essential for nitrogen fixation.

  Cortex primarily contributes to the formation of nodules, particularly in legume family.

High humidity restricts the transpiration because humid air is almost saturated with water vapour and cannot absorb much more by transpiration.

Nitrogenase enzyme is present in the root nodules of leguminous plants, which helps in the conversion of atmospheric free nitrogen into ammonia.

Trace element is an element that is required in minute quantities for physiological functioning.

 Rhizobium is a symbiotic bacteria present in the root nodules of leguminous plants. It contains the enzyme nitrogenase that helps in the conversion of atmospheric free nitrogen into ammonia.

Nitrobacter bacteria play a major role in the nitrogen cycle, mostly by transforming nitrites into nitrates. 

Cyanobacteria, also known as blue-green algae, are the primary organisms responsible for nitrogen fixation in aquatic habitats. They possess specialized cells called heterocysts to convert atmospheric nitrogen into usable forms.

The molecular structure of chlorophyll consists of a N-ring with a Mg center, side chains, and a hydrocarbon tail.

Land plants obtain carbon directly from the atmosphere in the form of carbon dioxide (CO2) during photosynthesis. Other elements like nitrogen and phosphorus are primarily absorbed from the soil.

Iron is essential for the synthesis of chlorophyll. Because iron is immobile within the plant, its deficiency first appears as interveinal chlorosis (yellowing between the veins) on young, developing leaves.

Exanthema is a physiological disorder in citrus plants caused by a deficiency of copper. It is characterized by the formation of gum pockets under the bark and the dying back of young twigs.

Although nitrogen is an essential nutrient, most plants cannot utilize nitrogen gas (N2) directly from the air. They must absorb nitrogen from the soil in the form of nitrates or ammonium ions.

Ferredoxins are iron-sulfur proteins that act as electron carriers in various metabolic processes, most notably in the light reactions of photosynthesis. The name is derived from 'ferrum', the Latin word for iron.

The middle lamella is the outermost layer of the plant cell wall that glues adjacent cells together. It is primarily composed of calcium and magnesium pectates.

Micronutrients are essential elements required by plants in very small quantities. Zinc (Zn) is a micronutrient, while Magnesium (Mg), Phosphorus (P), and Potassium (K) are macronutrients required in larger amounts.

Martinus Willem Beijerinck was a Dutch microbiologist and botanist. In 1901, he discovered that symbiotic nitrogen fixation is done by rhizobium.

Water is the primary component of all living cells, typically accounting for 70% to 90% of their total mass. It serves as a universal solvent for biochemical reactions and provides structural turgidity to the cell.

Leguminous plants have a symbiotic relationship with nitrogen-fixing bacteria, most notably Rhizobium. These bacteria reside in specialized nodules formed on the roots of the plant, converting atmospheric nitrogen into a form the plant can absorb.

Cajanus cajan, commonly known as pigeon pea or arhar, is a leguminous crop. Because it can fix atmospheric nitrogen through root nodules, it is capable of growing in nitrogen-deficient soils without the need for external fertilizers.

Plants primarily absorb iron from the soil in the form of ferric ions (Fe3+). While some plants can reduce it to the ferrous form (Fe2+) for easier uptake or metabolic use, the ferric form is the standard state for absorption in most soil conditions.

NPK stands for Nitrogen (N), Phosphorous (P) and Potassium (K). 

Azotobacter fixes atmospheric nitrogen, lightning converts nitrogen into oxides, and bacterial decay releases nitrogen from organic matter. Lime (calcium carbonate) is used to neutralize soil acidity and does not provide nitrogen compounds.

Magnesium is the central metallic atom in the chlorophyll molecule, making it structurally essential. Iron is not part of the chlorophyll structure itself but is a critical cofactor for the enzymes that catalyze its biosynthesis.

Phosphorus is a fundamental component of the sugar-phosphate backbone in DNA and RNA. It is also found in ATP and phospholipids, but it is not a structural part of simple proteins or carbohydrates.

Ammonification is the conversion of organic nitrogen to ammonium (NH4+) by the action of decomposers (bacteria).

Biological nitrogen fixation, particularly by symbiotic bacteria like Rhizobium in legume nodules, accounts for the vast majority of nitrogen fixed in nature. This process far exceeds the amounts fixed by lightning or industrial processes.

Potassium (K) is not a structural component of any organic compound in plants, but it acts as a vital activator for over 60 enzymes. It also plays a key role in maintaining osmotic balance and stomatal movement.

While plants can absorb nitrogen as ammonium, the most common and abundant form of nitrogen uptake from the soil is nitrate (NO3-). Nitrates are highly soluble and easily transported through the plant's xylem.

Plants obtain carbon primarily from atmospheric carbon dioxide (CO2) during photosynthesis. This carbon is fixed into organic molecules like glucose, which serve as the building blocks for the plant's structure and energy.

Potassium is essential for plant health because it activates numerous enzymes that regulate metabolic processes like protein synthesis and photosynthesis. It also maintains cell turgor and regulates the opening and closing of stomata.

 Rhizobium is the most commom symbiotic bacteria, which carry out the nitrogen fixation.

Necrosis refers to the localized death of plant tissue, often appearing as brown or black spots on leaves. Deficiencies in mobile macronutrients like Potassium (K) and Magnesium (Mg), as well as Calcium (Ca), frequently manifest as necrotic areas.

Micronutrients are required by plants in very small quantities, but they are just as essential for growth and reproduction as macronutrients. A deficiency in a micronutrient can lead to severe physiological disorders or death.